Dr. Andy

Reflections on medicine and biology among other things

Wednesday, December 14, 2005

Genes, chemicals, and cancer

Two articles in the NYTimes today about cancer and what causes it, one focusing on environmental exposure to chemicals and the other on a new initiative to comprehensively examine the genes involved in various cancers.

In contrast to much of the hysteria out there about environmental exposures, the first article points out how little evidence there is linking environmental exposures to cancer:
Rates of cancer have been steadily dropping for 50 years, if tobacco-related cancers are taken out of the equation, said Prof. Richard Peto, an epidemiologist and a biostatistician at Oxford University.

What appear as increases in cancers of the breast and prostate, Dr. Peto added, are in fact artifacts of increased screening. When healthy people are screened, the tests find not only cancers that would be deadly if untreated, but also a certain percentage of tumors that would never cause problems if let alone.

His analysis of cancer statistics leads Dr. Peto to this firm conclusion: "Pollution is not a major determinant of U.S. cancer rates."
The article goes on to, in a nice way, expose the lack of sophistication of many "believers" in the exposure-cancer risk. Not being scientists, they don't have any evidence, but rely instead on emotion:
Barbara Brenner, executive director of the Breast Cancer Action Coalition, an advocacy group in San Francisco, said that at the very least people should look for the least toxic alternative to chemicals in common use that may cause cancer.

Having had breast cancer twice, Ms. Brenner is impassioned by the cause. "I have a firsthand experience, and I would do anything - anything - to keep someone else from having that experience," she said.

Of course, how do you know what the least toxic alternative is?

None of this is to say that the environment plays no role in cancer, it certainly can (think second hand tobacco smoke), but that the role is likely small. The article describes some ongoing research into unravelling the connection.

The second article details a new initiative to find genetic mutations in specific cancers. The search has been spurred on by the success of imatinib (Gleevac) which inhibits a specific altered protein in certain leukemias and GI tumors. It has been a stunning success, the exemplar of the utility of targeted molecular therapies for cancer.

The new initiative is huge, a 3 year pilot study budgeted for $100million to focus on 2 or 3 types of cancer (you can bet breast will be one). The full study would run 9 years and cost more than a billion dollars.

This seems like a lot of money, given how many other smaller research projects you could fund.


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