It is likely that, in the near future,
a sample of an individual’s cancer will be carefully and extensively analyzed
in the laboratory before any therapy is started. The results of this analysis
will allow us to select a treatment that will likely work the first time. By matching drugs to the specific defects in
an individual human being’s cancer, we should be able to avoid the “trial and
error” approaches of today.
In 2011, two new cancer treatments
were approved that illustrate this new paradigm. Crizotinib (Xalkori®)
was approved for the treatment of lung cancer that harbors a specific mutation
in the ALK gene. Vemurafenib (Zelboraf®) was approved for the
treatment of melanoma, the deadliest form of skin cancer. This drug targets BRAF—a protein that is mutated in nearly
half of melanomas and drives the cancer’s growth. Both of these drugs will only be helpful to people whose cancer carries the target mutation and that is why the drugs were approved together with a test to determine if an individual person's cancer is likely to be susceptible.
We
will see many more such drug–test combinations, and they promise to bring much
better results to cancer patients. The approval of these two drugs shows that
the era of personalized medicine has begun to arrive.
These targeted therapies are encouraging developments and undoubtedly will help many people! Thank you for offering such a valuable resource here to those of us out here looking for guideposts in what is at times a confusing and dark night. I look forward to your book and understanding more about the world of clinical trials in cancer treatment.
ReplyDeleteI have a question about clinical trials specifically for maintenance therapies. I was specifically interested in pancreatic cancer and have recently seen a quote by a well-regarded oncologist at the Mayo Clinic who specializes in gastrointestinal saying that he used maintenance therapies in cases of inoperable stage iv colon cancer patients who had achieved successful results after an initial chemo regimen. He goes on to say the evidence is just circumstantial but that giving the patient a complete break from of therapy is probably not a good idea (when they are tolerating it well and risk/benefit is clearer). Do you see any general trends or new developments in the study of maintenance chemotherapies?
Thanks for the comment. The use of maintenance chemotherapy is another area where there is no "one size fits all" answer, but there is quite a bit of history on this topic. In fact 20 to 30 years ago, it was common practice to treat patients with many cancers with extended chemotherapy. Studies then began to show that similar benefits were achievable with shorter duration of therapy in many cases. That is how, for many cancers, maintenance therapy became uncommon. This did not happen for all cancers, however. In some leukemias, for example, chemotherapy for 1 or even 2 years remains the standard of care. With newer agents, the idea of long term maintenance has had a bit of renaissance. For example, in some cancers, the anti-angiogenic drug bevacizumab can be prescribed as maintenance even when chemotherapy is completed. The immunotherapy drug ipilimumab, recently approved for melanoma, is also being studied in this way. These are just a couple of examples. So, in some situations, there is clearly a role for extended therapy, but to be sure, we need clinical trials to quantify the benefits and the side effects and make sure the balance favors maintenance therapy. All the best.
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