WO2006078770A2

WO2006078770A2 - Creating temporary space between body tissues

Info

Publication number: WO2006078770A2
Application number: PCT/US2006/001826
Authority: WO
Inventors: Winston E. Barzell
Original assignee: Civco Medical Instruments Co., Inc.
Priority date: 2005-01-21
Filing date: 2006-01-20
Publication date: 2006-07-27
Also published as: WO2006078770A3

Abstract

A method for treating a prostate with radiation includes: introducing a fluid into a potential space defined between two layers of fascia to contact the two layers; forming a bioresorbable spacer from the fluid to provide an increased spacing of the prostate and a rectum from one another beyond natural spacing thereof; applying radiation therapy to the prostate after introducing the fluid into the potential space; maintaining a minimum spacing between the prostate and the rectum with the bioresorbable spacer for a desired time period of at least forty-eight hours, wherein the minimum spacing is greater than the natural spacing.

Description

CREATING TEMPORARY SPACE BETWEEN BODY TISSUES

FIELD OF THE INVENTION

This invention relates generally to the creation of temporary space between body tissues. The present invention also relates, for example, to the use of a biodegradable spacer between the rectum and prostate prior to delivering external radiation therapy in the treatment of prostatic cancer.

BACKGROUND OF THE INVENTION Prostate cancer is a relatively radioresistant malignancy, but can be effectively treated with radiation if a high dose can be delivered. The major risk to the delivery of high doses of radiation to the prostate is collateral radiation damage to surrounding structures, the rectum being the most vulnerable. The rectum is susceptible because of the very close natural anatomic proximity of the posterior surface of the prostate and the anterior rectal wall and the comparative radiation sensitivity of the bowel. Radiation proctitis is the major limiting factor for the radiation therapist using this modality. This type of proctitis may occur acutely during treatment and/or develop later as chronic and progressive radiation induced inflammatory reaction of the rectal wall that can cause diarrhea, rectal pain, tenesmus, bleeding and in the worst case, a recto-urethral fistula. Currently, it is believed that domestically well over 100,000 patients annually are treated with external beam radiation therapy either as monotherapy or in combination with implanted radioactive seeds (brachytherapy). In every case the concern with rectal overdose puts constraints on the achievement of optimal therapy.

The natural anatomic tissues that exist between the posterior surface of the prostate and the anterior rectal wall include two very thin but consistent fibrous layers or planes that define a potential space. These layers were discovered by anatomic dissection over 100 years ago and routinely are taken advantage of surgically to separate the prostate from the rectum in many operations. These layers have been variously described as "Denonvillier's fascia" or "Denonvilliers' fascia" or a "biplane fascial layer." It has been shown, however, that the two macroscopically and generally readily separable layers that are disposed between and separate the prostate and the rectum are actually appropriately described in an anatomical sense as (1) the fascia propria of the rectum, containing the mesorectum, and (2) the true Denonvilliers' fascia covering the prostate and seminal vesicles. See, e.g., I. Lindsey et al, "Anatomy of Denonvilliers' fascia and pelvic nerves, impotence, and implications for the colorectal surgeon," British Journal of Surgery 2000, 87, 1288-1299. This article by Lindsey et al. is incorporated herein in its entirety.

In recent years transient filling of the potential space between these two separable layers has been exploited using saline or a temporary balloon to separate the rectal wall from the prostate for acute one-time therapies such as cryotherapy or microwave thermotherapy. During cryotherapy for example, in one technique a long needle may be inserted through the perineum while the patient is in the lithotomy position. Using a real time image from a transrectal ultrasound probe for visual guidance, the needle tip may be placed into this potential space between the layers of Denonvillier's fascia and fluid instilled. The fluid then hydraulically dissects and fills this potential space to create a pillow shaped "balloon" of liquid separating the prostate and rectum. The filled space between the two fascial layers can achieve one or a few centimeters of additional separation of the rectal wall and prostate when compared to normal anatomic proximity. This transient separation improves the safety margin for avoiding rectal injury during treatment. One potential consequence of this dissection is scarring and adhesion making subsequent attempts to repeat this process more difficult.

An example of a known method of treatment is described in U.S. Patent No. 6,064,914 which is entitled Thermotherapy Method and issued to John R. Trachtenberg. This patent, which is incorporated herein in its entirety, concerns an apparatus for the treatment of the prostate. As explained in this patent, because the rectum naturally lies in intimate contact with the prostate and the biplane fascial layer, if one subjects the periphery of the prostate to intense thermal therapy to kill living tissue within, one risks damaging the portions of the rectum close to the prostate. This patent instead describes the injection of fluid flow under pressure into the biplane fascial layer so as to create a space. Energy source therapy can then be applied to the prostate for thermal therapy. However, this method and device of operation would not be applicable for external radiation therapy which typically lasts 6 to 8 weeks since the Trachtenberg tissue spacer is impractical and indeed would be associated with numerous complications including infection. An example of a method employing saline is described and illustrated in Gary Onik, "Image Guided Prostate Cryosurgery: State of the Art," Cancer Control, Nov-Dec 2001 , Vol. 8, No. 6, pp. 522-531 , which is incorporated herein in its entirety. See also U.S. Patent No. 5,733,316 and its U.S. Reissued Patent No. RE38,143 E to Tierney et al. and directed to organ separation for thermal therapy, also incorporated herein in their entirety.

U.S. Patent No. 6,210,314 Bl to Ein-Gal is directed to a prostate radiotherapy apparatus for spatially fixing a target volume in a prostate which is to be irradiated. As safety features, this patent describes the injection of water in the area of Denonvilliers' fascia for reflecting the rectal wall away from the prostate and provision of cooling in the area of the prostate to reduce the adverse effects of radiation on healthy tissue, e.g., the rectal wall or urethra. This patent also is incorporated herein by reference. The use of biodegradable materials has been known, for example, in the marking of biopsy sites, as exemplified in U.S. Patent No. 6,567,689 B2, which is incorporated herein in its entirety. However, this patent falls short of the present inventions which relate to the treatment of the prostate.

The present invention provides for a more convenient and efficient method of creating a temporary biodegradable spacer between the rectum and the prostate. After the spacer is inserted, the prostate can be treated, for example, by radiation therapy with minimal or negligible harm to the rectum.

SUMMARY OF THE INVENTION The invention relates to a method for treating a prostate with radiation comprising: introducing a fluid into a potential space defined between two layers of fascia to contact the two layers; forming a bioresorbable spacer from the fluid to provide an increased spacing of the prostate and a rectum from one another beyond natural spacing thereof; applying radiation therapy to the prostate after introducing the fluid into the potential space; maintaining a minimum spacing between the prostate and the rectum with the bioresorbable spacer for a time period of at least one month, wherein the minimum spacing is greater than the natural spacing. The method may further include at least one of: allowing the prostate and the rectum to return to natural spacing thereof as the bioresorbable spacer is broken down in vivo; piercing at least one of the two layers of fascia to introduce the fluid into the potential space; obtaining an ultrasound image to determine whether the fluid is disposed in the potential space; obtaining an ultrasound image to determine whether the bioresorbable spacer is maintaining the minimum spacing; conducting x-ray fluoroscopy to determine whether the fluid is disposed in the potential space; conducting x-ray fluoroscopy to determine whether the bioresorbable spacer is maintaining the minimum spacing; obtaining imaging to determine whether the fluid is disposed in the potential space; obtaining imaging to determine whether the bioresorbable spacer is maintaining the minimum spacing.

The rectum has a rectal wall and in some embodiments when radiation therapy is applied to the prostate less than 50% of the rectal wall receives a dose of radiation no more than 55 Gy when the minimum spacing is maintained. In some embodiments, when radiation therapy is applied to the prostate less than 20% of the rectum receives a dose of radiation no more than 65 Gy when the minimum spacing is maintained.

The radiation therapy may deliver a dose of radiation to the prostate of at least 80 Gy, and the radiation therapy may be external beam radiation therapy and/or brachytherapy. The fluid may include a liquid or a gel. hi some embodiments, the minimum spacing may be maintained for a time period of at least two months or at least three months. The minimum spacing, for example, may be at least 0.5 cm, at least 1.0 cm, at least 1.5 cm, or at least 2.0 cm. The fluid may be introduced into the potential space by injection.

The fluid may include a beneficial agent. In some embodiments, the fluid may include a therapeutic agent such as an anti-inflammatory agent.

The fluid may include a plurality of components that interact to form the spacer. In some embodiments, the spacer is sponge-like. In some embodiments, the spacer is at least partially solid. The invention also relates to a method for providing temporarily increased spacing between a prostate and a rectum during radiation therapy including: introducing a volume of bioresorbable composition into a region between two layers comprising the fascia propria of the rectum and the Denonvilliers' fascia to directly contact the layers and exert pressure thereon, the volume selected to provide spacing of the prostate and the rectum from one another by at least 5.0 mm; applying radiation therapy to the prostate after introducing the volume of bioresorbable composition into the region; maintaining the at least 5.0 mm of spacing between the prostate and the rectum as a result of introduction of the bioresorbable composition for a time period of at least one week. The method may further include one or more of: allowing the prostate and the rectum to return to natural spacing thereof as the bioresorbable composition is broken down in vivo; piercing at least one of the two layers to introduce the bioresorbable composition into the region; obtaining an image to determine whether the bioresorbable composition is maintaining the at least 5.0 mm of spacing between the prostate and the rectum. The rectum may have a rectal wall and when radiation therapy is applied to the prostate less than 50% of the rectal wall receives a dose of radiation no more than 55 Gy when the spacing is maintained. Also, when radiation therapy is applied to the prostate less than 20% of the rectum may receive a dose of radiation no more than 65 Gy when the spacing is maintained. The radiation therapy may deliver a dose of radiation to the prostate of at least 80 Gy and the radiation therapy may be external beam radiation therapy and/or brachytherapy. The composition may include a fluid. In some embodiments, the composition may include a liquid or a gel.

The present invention also relates to a rectal spacing implant including an injectable volume of fluid for providing a bioresorbable mass adapted to directly contact anatomical layers defining recto-prostatic space while providing and maintaining a mass thickness of at least 5.0 mm between portions of a prostate and a rectum for at least one week before break down thereof. In some embodiments, the bioresorbable mass may be sponge-like. In some embodiments, the bioresorbable mass may be at least partially solid. In addition, the present invention relates to a rectal spacing implant including an injectable volume of fluid for providing a bioresorbable mass adapted to directly contact anatomical layers defining recto-prostatic space while providing and maintaining a mass thickness of at least 5.0 mm between portions of a prostate and a rectum for at least forty-eight hours. In some embodiments, the bioresorbable mass may be sponge-like. In some embodiments, the bioresorbable mass may be at least partially solid. Further, the present invention relates to a radiation treatment system including: a radiation seed; and a rectal spacing implant including an injectable volume of fluid for providing a bioresorbable mass adapted to directly contact two layers of fascia defining recto-prostatic space, the bioresorbable mass capable of providing and maintaining a separation of at least 5.0 mm between portions of the two layers of fascia for at least forty-eight hours. In some embodiments, the bioresorbable mass may be sponge-like. In some embodiments, the bioresorbable mass may be at least partially solid. Also, in some embodiments, the bioresorbable mass may be capable of providing and maintaining a separation of at least 5.0 mm between portions of the two layers of fascia for at least one week. In addition, the present invention relates to a process for treating the prostate with radiation which process comprises the creation of a temporary space between the rectum and the prostate by preparing a biodegradable member having a predetermined lifetime and injecting said biodegradable member between the two layers of fascia separating the prostate and the rectum so as to develop a space between the prostate and the rectum, and applying radiation therapy after the creation of the temporary space with the biodegradable member. The biodegradable member may help to protect the rectum from damage that may result from the radiation.

BRIEF DESCRIPTION OF THE DRAWING Preferred features of the present invention are disclosed in the accompanying drawings, wherein:

FIG. 1 illustrates a side view of a prostate and a rectum; FIG. 2 illustrates a front view of the prostate and rectum physically separated by fluid according to the prior art; and FIG. 3 is a schematic illustration in cross-sectional side view of fluid disposed between two layers of fascia according to the present invention (not shown to particular scale of desired spacing necessarily provided by the fluid). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description which follows, any reference to direction or orientation is intended primarily and solely for purposes of illustration and is not intended in any way as a limitation to the scope of the present inventions. Also, the particular embodiments described herein, although being preferred, are not to be considered as limiting of the present inventions.

As used herein, the term "two layers of fascia" means the two macroscopically and generally readily separable layers that are disposed between and separate the prostate and the rectum, described in an anatomical sense as (1) the fascia propria of the rectum, containing the mesorectum, and (2) the true Denonvilliers' fascia covering the prostate and seminal vesicles.

As used herein, the term "potential space" means a region of adjustable size defined between the two layers of fascia. The size may be adjusted by insertion of fluid between the two layers of fascia to increase the spacing therebetween.

As used herein, the term "fluid" means a composition that may be in the form of a liquid, gel, slurry, or combination thereof and which optionally may have bubbles therein containing gas such as air. Fluids also include pastes and viscous suspensions. The fluid is flowable so that it may be dispensed from a delivery device such as a needle.

As used herein, the term "beneficial agent" is intended to have its broadest possible interpretation and is used to include any drug or therapeutic agent.

As used herein, the terms "drug" and "therapeutic agent" are used interchangeably to mean any therapeutically active substance that is delivered to an anatomical region of a living being to produce a desired, usually beneficial, effect. For example, the therapeutic agent may be an anti-inflammatory agent or another agent for addressing common side effects of radiation treatment for prostate cancer including irritation of the skin around the rectum, bowel irritability including mild diarrhea, gas, bowel urgency, and tenderness, increased urinary frequency, and mild burning with urination. The therapeutic agent also may be an anti-infection agent such as an antimicrobial agent. As used herein, the terms "bioresorbable" and "biodegradable" are used interchangeably to refer to a composition that can be broken down by either chemical or physical process, such as a biological process, upon interaction with a physiological environment. A bioresorbable fluid, bioresorbable mass, or bioresorbable spacer of the present invention may be broken into components that are metabolizable or excretable, over a period of time from minutes to years, while maintaining any requisite anatomical spacing in that same time period.

As used herein, the term "spacer" refers to a mass, formed of solid, semisolid, fluid, or combinations thereof, that provides spacing between anatomical portions. The present invention is directed to a method of injecting a biodegradable spacer in place of the fluid separator 10 in the recto-prostatic space between the rectum 12 and prostate 14, as shown in FIGS. 1 and 2, prior to delivering external radiation therapy in the treatment of prostatic cancer. The spacer aids in protecting the rectum from the harmful effects of radiation while allowing for maximizing the dose of radiation to the prostate.

External radiation therapy is a recognized modality for treating patients with prostate cancer. Approximately 125,000 patients undergo this procedure in the United States per year. While most prostate cancers are theoretically curable with radiation if enough radiation is given, the limiting factor is toxicity to adjacent structures, notably the rectum. Because of this, radiation to the prostate in the past, in the linear accelerator era, was only able to safely deliver between 65.00-68.00 Gy (gray) to the prostate without adversely affecting the rectum. Unfortunately, this dose was insufficient in curing a significant proportion of cancers. In an effort to increase the dose of radiation while minimizing collateral damage to the rectum, 3-D conformal radiation was started in the 1990s and a total dose of 70.2-75.6 Gy was accomplished by blocking out the rectum after the 70 Gy dose had been delivered. Most recently, in the current era, IMRT (intensity-modulated radiation therapy) has attempted to further decrease the radiation damage to the rectum by a computer modulated radiation delivery system. Now, doses of 75.6-78.0 Gy can be given with acceptable rectal complications. Despite these attempts, the proximity of the rectum to the prostate, with a natural spacing of 1-2 mm from each other, is the limiting factor in delivering adequate radiation to the prostate. The toxic dose to the rectum is approximately 65 Gy and, as long as less than 20% of the rectum gets less than 65 Gy, rectal complications are reduced to less than 5%. The complications to the rectum are thought to be negligible if less than 50% of the rectal wall gets no more than 55 Gy. It is estimated that a 1 centimeter (cm) separation between the rectal wall and the prostate results in about a 10% reduction of the dose to the rectum; a 1.5 cm separation results in about 15-20% reduction of the dose; and a 2 cm separation in about 30-35% reduction in the dose to the rectum.

Thus, there is a major theoretical "cap" on the amount of radiation that can be delivered to the prostate because of the proximity of the prostate capsule to the rectal mucosa. These two organs are separated by a minimal amount of fat, and by the readily separable two layers of fascia. This anatomic fact has led to the current use of saline to separate the rectum from the prostate during cryosurgery. During cryosurgery, a recognized and approved treatment for prostate cancer, saline may be injected into the potential space between the two layers of fascia prior to freezing the prostate in an effort to protect the rectum from freeze injury. This saline is quickly resorbed and repeated injections are necessary during the procedure.

According to the present invention, a biodegradable tissue spacer can be injected into the potential space between the two layers of fascia to develop the space between the prostate and rectum and thus separate the rectal wall from the prostate capsule. For example, the biodegradable tissue spacer can be injected in place of the fluid separator shown in FIG. 1 between the prostate 14 and the rectum 12. Biodegradable materials are currently in wide use in medicine and, by varying the chemical composition, one can provide for a precise "lifetime" in tissue.

As shown in FIG. 3, according to the present invention fluid 20 may be injected or otherwise delivered, such as by needle 22, to provide increased separation between rectal wall 12a of the rectum and the prostate/seminal vesicles 14a. In particular, fluid 20 may be delivered to the potential space between the fascia propria of the rectum 12b, containing the mesorectum 12c, and the true Denonvilliers' fascia 15. In one preferred embodiment of the present invention, a biodegradable agent with a 3-4 month expected duration is used so that the amount of spacer remains generally constant during the approximate 6-8 weeks that it takes to complete a course of external radiation therapy. In this fashion, larger doses of radiation to the prostate can be achieved with improved overall cure rates, but diminished side effects on the rectum. The fluid used in creating the expanded potential space, for example, may comprise or be derived from collagen collected from any number of mammalian sources and maybe an injectable, aqueous suspension of cross-linked, quenched collagen. One such preferred biodegradable material includes a sterile, cross-linked, bovine-derived collagen marketed as Contigen® Bard® Collagen Implant available from C. R. Bard, Inc. Preferably, the fluid dispensed to the potential space is reabsorbed over time. A variety of other fluids are contemplated such as a biodegradable gels of hyaluronic acid or hyaluronic acid derivatives, or hydrogels. The fluid may, for example, be catabolized. In some embodiments, the fluid may include one or more components selected from the group consisting of collagen, gelatin, albumin, chondroitin sulfate, hyaluronic acid, heparin, oxidized cellulose, dextran, polyglycolic acid, polylactic acid, and polyanhydride.

In summary, therefore, what is proposed by this invention is to inject a biodegradable spacer with a predetermined known half-life in tissue preferably into the potential space between the two layers of fascia — the fascia propria of the rectum, containing the mesorectum, and the true Denonvilliers' fascia covering the prostate and seminal vesicles — and thus to separate the rectum from the prostate capsule by about 1 -2 cm or more. This would allow higher doses of radiation to the prostate in the 80+ Gy range with minimal, if any, side effects on the rectum. It is widely accepted that if one can deliver doses of 80+ Gy to the prostate most prostate cancers could be cured by this modality.

Thus the present invention includes the application of a method for separating the rectal wall 12a from the prostate 14a during external beam radiation therapy. The method demands that greater than normal anatomic separation between the posterior aspect of the prostate and the rectal wall be maintained over a period of weeks rather than the transient period using currently available methods which typically provide some separation for less than about 24 hours. To accomplish this, the present inventions, instead of saline or other quickly absorbed or dispersed liquids, involve the use of a more viscous or more slowly absorbed or dispersed substance. As noted generally, there are numerous compounds in several classes of approved biocompatible materials that can serve as a fluid for injection into the potential space between the two layers of fascia and that would achieve a generally sufficiently long lasting filling of the space. Preferably the substance chosen for the fluid may dissolve or be metabolized over time, so that the normal anatomic positions of the two layers of fascia may be restored eventually.

In a preferred exemplary embodiment of the present invention, once fluid is injected into the potential space, it forms a bioresorbable spacer. The bioresorbable spacer, for example, may be formed when the fluid is transformed, e.g. through chemical reaction, to sponge-like or other at least partially solid compositions in vivo. Such a bioresorbable spacer may provide a matrix that optionally may be porous and that may separate the two layers of fascia from each other by a desired distance, e.g. at least 0.5 mm, for a desired time period, e.g. at least forty-eight hours, before gradually losing the ability to maintain such a separation.

Also, preferably the substance chosen for the fluid could be radiolucent and relatively pliable for anatomic conformance. The substance chosen for the fluid may be delivered, for example, using a needle positionable between the two layers of fascia using a template grid as described in United States Patent Application Publication No. US 2004/0143150 Al to Barzell et al. directed to a template grid system, which is incorporated herein in its entirety.

External beam radiation therapy is delivered in once or twice a day fractional doses over a period of about 4 to 6 weeks or more. The typical saline induced separation of the two layers of fascia is very transient lasting less than one hour unless additional fluid is instilled. The balloon method which is described for example in U.S. Patent No. 6,064,914 is also transient with a placement duration of several hours.

The present inventions propose using an injectable substance that will function as a spacer in this anatomic compartment between the prostate and rectum for a finite residence time therein for a period of weeks or months. In the present invention, the injected fluid preferably is bioresorbable and is broken into components that are metabolizable or excretable, over a period of time of at least one week such as between one week and one year, and more preferably between one month and three months, while maintaining any requisite anatomical spacing in that same time period. Preferably, the injected fluid maintains the desired anatomical spacing for the entire multi-week period during radiation therapy.

The placement or injection of this substance preferably can be performed using real time imaging such as ultrasound or x-ray fluoroscopy. Confirmation of the persistence of this artificial spacer may be done using ultrasound, CT, MRI or other modality. Because of the inverse square relationship of radiation dose with distance from the target, the modest degree of separation achieved by this exemplary method will greatly reduce the risks of rectal morbidity from prostate irradiation and allow higher, potentially more effective doses to be delivered. The present inventions will be very well accepted by radiation oncologists because of the potential for improving radiation therapy outcomes in patients with prostate cancer.

Although the two layers of fascia may not themselves create a completely enclosed region that would limit migration of fluid delivered to the potential space, surrounding anatomy combined with the two layers of fascia acts to limit such migration so that the fluid maintains desired spacing between the two layers of fascia prior to bioresorption causing loss of an ability of the fluid to otherwise maintain such desired spacing. Delivery of the fluid expands the potential space to provide a desired spacing between the prostate and rectum. Once the fluid is delivered, it is generally static in the potential space, e.g., it is not continuously recirculated as is the case with some balloon catheters of the prior art inserted between the two layers of fascia and employing saline as the fluid.

During delivery of the fluid to the potential space, at least one of the two layers of fascia may be pierced by the delivery device such as a needle. Although the spacing of the two layers of fascia has been described herein in connection with external beam radiation therapy, the present invention may be used in connection with other forms of radiation therapy including low dose rate (LDR) brachytherapy and high dose rate (HDR) brachytherapy. For example, radiation may be delivered interstitially using radioactive seeds. A radioactive seed has a radioactive material with a half-life defined as the amount of time it takes for half of the radioactive material to decay. Iodine- 125, for example, has a half life of about sixty days, while Palladium- 103 has a half-life of about 17 days and Iridium- 195 has a half-life of about 72 days. ^■ In some exemplary embodiments of the present invention, where a radioactive seed is delivered to the prostate for radiation treatment, the two layers of fascia preferably are spaced apart as described above for at least the half-life of the radioactive material of the seed. More preferably, the two layers of fascia are spaced apart as described above for at least two times the half-life of the radioactive material of the seed, and in some embodiment, for between two and six times the half-life. In instances where the seed may be implanted for a period of less than one week at a time, for example 48 hours (2 days) at a time, preferably the two layers of fascia are spaced apart for at least the time period during which the seed is disposed in or proximate the prostate. While various descriptions of the present invention are described above, it should be understood that the various features can be used singly or in any combination thereof. Therefore, this invention is not to be limited to only the specifically preferred embodiments depicted herein.

Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. For example, in some exemplary embodiments of the present invention, the fluid(s) delivered to the potential space remain in fluid form for the desired period of time before no longer no longer being able to maintain desired spacing between the two layers of fascia. In other exemplary embodiments, some fluid(s) delivered to the potential space may transform to sponge-like or other at least partially solid compositions in vivo while being bioresorbable and losing an ability to maintain desired spacing between the two layers of fascia after a finite time therein of at least one week, and in some embodiments of at least one month. Injectable and bioerodible polymers may be used in accordance with the present invention to provide a body of solid gel polymer to undergo degradation, erosion and solubilization as a result of hydrolysis of labile linkages at the physiologic conditions of use, after providing the desired spacing for the desired period of time when disposed in the potential space as described above. In addition, although the present invention is described for use in the potential space between two layers of fascia in connection with radiation therapy of the prostate, the present invention may be applied in connection with separating other anatomical regions during radiation therapy and thus may be applied to therapies other than prostate cancer treatment. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly defined as set forth in the appended claims.

Claims

The Claims What is claimed is:

1. A method for treating a prostate with radiation comprising: introducing a fluid into a potential space defined between two layers of fascia to contact the two layers; forming a bioresorbable spacer from the fluid to provide an increased spacing of the prostate and a rectum from one another beyond natural spacing thereof; applying radiation therapy to the prostate after introducing the fluid into the potential space; maintaining a minimum spacing between the prostate and the rectum with the bioresorbable spacer for a time period of at least one month, wherein the minimum spacing is greater than the natural spacing.

2. The method of claim 1 , further comprising: allowing the prostate and the rectum to return to natural spacing thereof as the bioresorbable spacer is broken down in vivo.

3. The method of claim 1, further comprising: piercing at least one of the two layers of fascia to introduce the fluid into the potential space.

4. The method of claim 1 , further comprising: obtaining an ultrasound image to determine whether the fluid is disposed in the potential space.

5. The method of claim 1 , further comprising: obtaining an ultrasound image to determine whether the bioresorbable spacer is maintaining the minimum spacing.

6. The method of claim 1 , further comprising: conducting x-ray fluoroscopy to determine whether the fluid is disposed in the potential space.

7. The method of claim 1 , further comprising: conducting x-ray fluoroscopy to determine whether the bioresorbable spacer is maintaining the minimum spacing.

8. The method of claim 1 , further comprising: obtaining imaging to determine whether the fluid is disposed in the potential space.

9. The method of claim 1 , further comprising: obtaining imaging to determine whether the bioresorbable spacer is maintaining the minimum spacing.

10. The method of claim 1 , wherein the rectum has a rectal wall and when radiation therapy is applied to the prostate less than 50% of the rectal wall receives a dose of radiation no more than 55 Gy when the minimum spacing is maintained.

11. The method of claim 1 , wherein when radiation therapy is applied to the prostate less than 20% of the rectum receives a dose of radiation no more than 65 Gy when the minimum spacing is maintained.

12. The method of claim 1 , wherein the radiation therapy delivers a dose of radiation to the prostate of at least 80 Gy.

13. The method of claim 1 , wherein the radiation therapy comprises external beam radiation therapy.

14. The method of claim 1 , wherein the radiation therapy comprises brachytherapy.

15. The method of claim 1 , wherein the fluid comprises a liquid.

16. The method of claim 1 , wherein the fluid comprises a gel.

17. The method of claim 1 , wherein the minimum spacing is maintained for a time period of at least two months.

18. The method of claim 1 , wherein the minimum spacing is maintained for a time period of at least three months.

19. The method of claim 1 , wherein the minimum spacing is at least 0.5 cm.

20. The method of claim 1 , wherein the minimum spacing is at least 1.0 cm.

21. The method of claim 1 , wherein the minimum spacing is at least 1.5 cm.

22. The method of claim 1 , wherein the minimum spacing is at least

2.0 cm.

23. The method of claim 1 , wherein the fluid is introduced into the potential space by injection.

24. The method of claim 1 , wherein the fluid comprises a beneficial agent.

25. The method of claim 1 , wherein the fluid comprises a therapeutic agent.

26. The method of claim 25, wherein the therapeutic agent is an antiinflammatory agent.

27. The method of claim 1 , wherein the fluid comprises a plurality of components that interact to form the spacer.

28. The method of claim 1 , wherein the spacer is sponge-like.

29. The method of claim 1 , wherein the spacer is at least partially solid.

30. A method for providing temporarily increased spacing between a prostate and a rectum during radiation therapy comprising: introducing a volume of bioresorbable composition into a region between two layers comprising the fascia propria of the rectum and the Denonvilliers' fascia to directly contact the layers and exert pressure thereon, the volume selected to provide spacing of the prostate and the rectum from one another by at least 5.0 mm; applying radiation therapy to the prostate after introducing the volume of bioresorbable composition into the region; maintaining the at least 5.0 mm of spacing between the prostate and the rectum as a result of introduction of the bioresorbable composition for a time period of at least one week.

31. The method of claim 30, further comprising: allowing the prostate and the rectum to return to natural spacing thereof as the bioresorbable composition is broken down in vivo.

32. The method of claim 30, further comprising: piercing at least one of the two layers to introduce the bioresorbable composition into the region.

33. The method of claim 30, further comprising: obtaining an image to determine whether the bioresorbable composition is maintaining the at least 5.0 mm of spacing between the prostate and the rectum.

34. The method of claim 30, wherein the rectum has a rectal wall and when radiation therapy is applied to the prostate less than 50% of the rectal wall receives a dose of radiation no more than 55 Gy when the spacing is maintained.

35. The method of claim 30, wherein when radiation therapy is applied to the prostate less than 20% of the rectum receives a dose of radiation no more than 65 Gy when the spacing is maintained.

36. The method of claim 30, wherein the radiation therapy delivers a dose of radiation to the prostate of at least 80 Gy.

37. The method of claim 30, wherein the radiation therapy comprises external beam radiation therapy.

38. The method of claim 30, wherein the radiation therapy comprises brachytherapy.

39. The method of claim 30, wherein the composition comprises a fluid.

40. The method of claim 30, wherein the composition comprises a liquid.

41. The method of claim 30, wherein the composition comprises a gel.

42. A rectal spacing implant comprising an injectable volume of fluid for providing a bioresorbable mass adapted to directly contact anatomical layers defining recto-prostatic space while providing and maintaining a mass thickness of at least 5.0 mm 6 001826

between portions of a prostate and a rectum for at least one week before break down thereof.

43. The implant of claim 42, wherein the bioresorbable mass is sponge-like.

44. The implant of claim 42, wherein the bioresorbable mass is at least partially solid.

45. A rectal spacing implant comprising an inj ectable volume of fluid for providing a bioresorbable mass adapted to directly contact anatomical layers defining recto-prostatic space while providing and maintaining a mass thickness of at least 5.0 mm between portions of a prostate and a rectum for at least forty-eight hours.

46. The implant of claim 45, wherein the bioresorbable mass is sponge-like.

47. The implant of claim 45, wherein the bioresorbable mass is at least partially solid.

48. A radiation treatment system comprising: a radiation seed; and a rectal spacing implant comprising an injectable volume of fluid for providing a bioresorbable mass adapted to directly contact two layers of fascia defining recto-prostatic space, the bioresorbable mass capable of providing and maintaining a separation of at least 5.0 mm between portions of the two layers of fascia for at least forty-eight hours.

49. The system of claim 48, wherein the bioresorbable mass is sponge- like.

50. The system of claim 48, wherein the bioresorbable mass is at least partially solid.

51. The system of claim 48, wherein the bioresorbable mass is capable of providing and maintaining a separation of at least 5.0 mm between portions of the two layers of fascia for at least one week.