Cigarettes May Have an Up Side
By Paul Recer
AP Science Writer
Tuesday, May 19, 1998; 4:03 p.m. EDT WASHINGTON (AP) -- Cigarettes may actually lower the risk of breast cancer among women with a gene mutation linked to high rates of the disease, a study indicates. But the researchers say other health risks of smoking far outweigh the possible benefits.
``Smoking may reduce breast cancer risk for these women, but cigarettes sharply increase the incidence of other cancers,'' said Jean-Sebastien Brunet, lead author of a study being published Wednesday in the Journal of the National Cancer Institute.
``This study is interesting scientifically, but it should not encourage anyone to smoke,'' said Brunet, a researcher at the Women's College Hospital of the University of Toronto in Canada.
The study examined the breast cancer history of 372 women who all had mutations of the BRCA1 or BRCA2 genes. By some estimates, about 80 percent of such women will develop breast cancer during their lifetime.
Half of the women in the study were smokers and half were nonsmokers.
Brunet said that the incidence of breast cancer was 54 percent lower among heavy smokers than among nonsmokers. The effect, he said, was ``dose related''; that is, the more a woman with a BRCA gene mutation smoked, the less likelihood of her developing breast cancer.
``If a woman smoked up to four pack years, the reduction was 35 percent,'' he said. ``For a four or more pack years, the reduction was 54 percent.''
A pack year is equal to smoking one 20-cigarette pack a day for a year. Four pack years would be four packs a day for a year or one pack a day for four years.
The study involved only women with the BRCA gene mutation. This mutation occurs, on average, in only one of every 250 women. Among some ethnic groups, the rate can be as high as one in 50. Between 5 percent and 10 percent of all women with breast cancer have a BRCA mutation.
Brunet said the study was scientifically valuable because it suggests that some action of smoking or of some of the 1,300 compounds in cigarette smoke may be protective against breast cancer. However, he said, ``we don't have any idea what that compound is.''
Some breast cancers have been linked to estrogen, the female hormone, and cigarette smoking is known to lower production of estrogen, said Brunet. Smoking also is linked to early menopause and to a decreased risk of endometrial cancer, Brunet said.
However, smoking significantly increases the risk of other, even more dangerous cancers, such of the lung, throat and pancreas.
Brunet said he and his 18 co-authors came to their conclusions reluctantly and only after putting the study results to rigorous statistical tests. Further, Brunet said that scientific referees on the Journal also carefully scrutinized the data.
``We did everything we could to test the data, but we would really like for someone to replicate the study just to prove that our data set is correct,'' he said.
In a commentary in the journal, Dr. John A. Baron of Dartmouth Medical School and Dr. R. W. Haile of the University of Southern California said that the study ``certainly should not be taken as encouragement for women with (the) mutations to smoke,'' but that it does raise the possibility that something in cigarette smoke could be of benefit for such women.
They said more research could lead to a drug that would protect against mutation-related breast cancer, but without the serious health risks of smoking.
© Copyright 1998 The Associated Press