Sunday, December 14, 2008

Gleevec: Explanation

I was talking with a friend about my previous entry about Gleevec, and found she’d come away with some confusion, an unintended interpretation. I’ll try to put my own understanding into better perspective and explain a bit more clearly.

Results of initial Gleevec testing with CML (Chronic Myeloid Leukemia) came as a surprise to researchers. Ten years ago they were only looking to verify its safety to test on people rather than its effectiveness; they weren’t expecting to find such high response rates in such early trials. But what they saw drove them to look at the patients more closely to see what was common about them. That’s when they discovered the “Philadelphia chromosome”, named for the lab where it was discovered. This chromosome malformation they had discovered led them to identify the first protein identified as a cancer-causing agent.

When they looked around at other cancers, they found similar reactions and high occurrence of the defective chromosome with GIST (Gastrointestinal Stromal Tumors). Soon after that, the FDA approved Gleevec for use with CML and GIST, making the drug commercially available.

In the meantime, other researchers in other types of cancers jumped on the bandwagon. Maybe they’d find a similar genetic mutation and the high response rates in their disciplines as well. Some of those other researchers, of course, dealt with melanoma.

There are experimental trials currently underway with melanoma to prove the concept. In order to get into such a trial, the drug company requires a four-week genetic workup to identify presence of the deformity. But the doctors on the battlefront have their own anecdotal evidence to identify who is most likely to be receptive to Gleevec treatment. My doctor and her geographically far-flung colleagues have independently observed that melanoma patients whose primary lesions start in two different ways tend to be the best candidates, while other, more “traditional” forms of skin lesions don’t usually respond. The responsive cancers start in moist places of the anatomy, or on the palms of hands and on the feet.

My doctor added her own 2-plus-2 and realized that I’d be an excellent candidate for Gleevec. She didn’t want us to wait four weeks for the drug company to come up their own verdict about me when her own intuition told her to go ahead. We were able to start me on the drug right away because it is commercially available.

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