Cleveland Indians pitcher Carlos Carrasco has recently been diagnosed with a form of blood cancer called chronic myeloid leukemia (CML). The disease, revealed during blood tests after the pitcher had reported feeling sluggish and lethargic, has a good prognosis, with 90% of people surviving for five years or more after diagnosis, according to the American Cancer Society. But until the early 2000's, CML had a substantially worse prognosis and Carrasco, had he been diagnosed a couple of decades ago, would likely not be resuming his conditioning and throwing training already, as has been reported.
This is thanks largely to one of the biggest breakthroughs in modern medicine to date, the development of the first targeted cancer drug called Imatinib (widely marketed by Novartis as Gleevec). Many conventional chemotherapy drugs, particularly those developed decades ago are not specific for cancer cells. More they target cells which are fast-dividing in preference to those which are dividing slowly, or not at all. Many of them are very effective in treating certain types of cancer, but unfortunately do come with numerous side-effects as any person who has had cancer will know. Cells which produce hair follicles and those which line the stomach and mouth are two examples of healthy fast-dividing cells which are often affected by conventional chemotherapies.
Imatinib was different.
All cancers are caused by faults in DNA called mutations, which result in uncontrolled growth of immature cells. In leukemia, these immature cells flood the blood system, taking up important room and resources that would otherwise be occupied by red blood cells (hence why many people with leukemia feel lethargic) and other, functioning immune cells. In CML, these cells have a particular genetic fault called a fusion protein where during cell division, two areas of DNA called genes, that have no business being anywhere near each other, get fused together. In CML, genes on chromosomes 9 and 22 get joined together, forming a mangled structure known as the Philadelphia chromosome. Imatinib was designed to lock onto a specific part of the Philadelphia chromosome and stop that cell from dividing. When first tested in humans, it produced stunning results, even in its first clinical trial and was one of the fastest-ever therapies to be FDA-approved back in 2001.
Dr Brian Druker, one of the researchers who led the development of Imatinib told the New York Times in 2009: "For a lot of people, Gleevec was simply too good to be true. But these once-dying patients were getting out of bed, dancing, going hiking, doing yoga. The drug was amazing.” Phase I clinical trials are largely to establish the safety profile of brand new drugs that have only previously been tested in animal models. However, remarkably, 98% of the patients on this initial trial were still alive five years after treatment and some of them are still alive today. A stunning result which has not been matched yet by any of the hundreds of other targeted cancer therapies approved, or in development, since.
Carrasco will almost certainly be on Imatinib, or one of the similar variants of the drug developed since the original FDA-approval in 2001 to treat his CML. Importantly for his athletic career, because the drugs are specific for the CML cells, in most people they come with minimal side-effects, especially when compared with conventional chemotherapies that are often used for other types of leukemia that do not have the Philadelphia chromosome. NHL player Brian Boyle was diagnosed with the same cancer in 2017 whilst playing for the New Jersey Devils and was able to continue his playing career after some brief time off.
Although coming with undoubtedly fewer side-effects than many cancer drugs, Imatinib and its variants are not flawless. It can cause some problems, especially when taken long-term as is the norm with most people with CML, but the majority of people taking it do well and experience minimal to no issues. If Carrasco is one of these people, he should be able to hopefully continue his MLB career unimpeded.
