The researchers reviewed 13 studies and concluded that passive smoke causes breast cancer. The report has created controversy because other major health groups, including the World Health Organization, reviewed the same material but did not reach the same conclusion.
The California scientists gave more weight to animal studies and recent human studies that better screened women for exposure to tobacco smoke, but indicting secondhand smoke may be difficult because scientists haven't proven that active smoking causes breast cancer.
"As new studies come in, it's quite possible all these agencies will be persuaded this is rock solid. But this is the first to come to that conclusion,"said Dr. Michael Thun, a representative of the American Cancer Society.
Dr. Jonathan Samet, the senior scientific editor for Surgeon General's Report says some scientists are uncomfortable with the balance of evidence and not quite so convinced as the state of California that it's leaning strongly toward the positive.
Cigarette maker R.J. Reynolds claimed, in written comments, that the report is flawed.T hey claim the researchers made errors, misinterpreted data and sometimes failed to explain how they analyzed the data.
Tobacco company Philip Morris said they're still deciding whether to comment. The surgeon general's new report on secondhand smoke is due out later this year.
The review found current literature, while incomplete, particularly in tumor biology, genetics, and inheritance patterns, does demonstrate epidemiological and clinical similarities between Africans and African Americans. African women are diagnosed most often between 35 and 45 years, and more than fifteen years earlier than women in Europe and North America. The mortality rate seen among women in sub-Saharan Africa is disproportionately high compared to the incident rate, as in African American women. Their tumors tend to be very aggressive with short periods of time between the onset of symptoms and diagnosis. Moreover, the tumors at diagnosis also tend to be higher grade, often involving axillary lymph nodes and, therefore, higher stages disease with worse prognoses. Poor prognosis is compounded by resource poor healthcare infrastructure, which offers limited treatment options and underutilizes effective treatments.
Still, the incidence of breast cancer in sub-Saharan Africa is small at 20 per 100,000 compared to 90 per 100,000 people in the West. The reason for this geographic disparity has much to do with protective behaviors that inadvertently minimize estrogen exposure, such as reproductive patterns, body build, and dietary patterns. The authors say as Africans adopt Western lifestyles, these protective behaviors are expected to be replaced with known risk factors for breast cancer.
The authors conclude, "The parallels between African American and Sub-Saharan African breast cancer patients suggests the possible effects of hereditary factors, and these influences may cause the younger age distribution that is seen among these patient populations to persist."
interscience.wiley/cancer-newsroom