Saturday, March 19, 2005

More on Vitamin A Causing Cancer

The asbestos arm of the asbestos and smoking chemoprevention study are critical to the asbestos compensation bill now before the Senate Judiciary Committee. BrooklynDodger will post on that soon. The overall study enrolled a large group of very heavy smokers as well as asbestos workers with all levels of smoking. Posted below is title information to lead you to the full abstract of that study.

The key conclusions were: "The previously reported adverse effects of beta-carotene and retinyl palmitate on lung cancer incidence and all-cause mortality in cigarette smokers and individuals with occupational exposure to asbestos persisted after drug [vitamin A] administration was stopped although they are no longer statistically significant.... the excess risks of lung cancer [in the post administration period, relative to other similarly exposed] were restricted primarily to females, and cardiovascular disease mortality primarily to females and to former smokers."

[The full text may be available from JNCI, a lot of the federal journals now have free web access.]

BrooklynDodger had previously opined that estimates of lung cancer effects of smoking should be modified to take into account the independent effect of newly identified carcinogens such as silica, diesel particulate matter, carbon black, metal oxides [as identified in welding fume] as well as synergistic effects. If carbon black is carcinogenic, then perhaps all particles are carcinogenic, including the massive particle exposure to cigarette smoke.

This study was launched based on diet studies in a general population [that is, a population without exposure assessment] which observed reduced lung cancer among those with high anti-oxident

BrooklynDodger suggests that an effect seen in females but not males may be an artifact of lower general population rates in females, and less variation in exposure in the females, rather than a real differential effect between men and women.


J Natl Cancer Inst. 2004 Dec 1;96(23):1743-50.

The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer
and cardiovascular disease mortality during 6-year follow-up after
stopping beta-carotene and retinol supplements.

Goodman GE, Thornquist MD, Balmes J, Cullen MR, Meyskens FL Jr, Omenn
GS, Valanis B, Williams JH Jr.
Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. North, Bldg.
M, M1-B514, Seattle, WA 98109, USA.

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