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Breast cancer link to smoking at puberty GIRLS who smoke, or are exposed to passive smoking, around the time of puberty may be at considerably increased risk of developing breast cancer in later life, a conference in Melbourne is to hear today.
Anti-Cancer Council of Victoria director Robert Burton said data from a US study, recently published in the American Journal of Epidemiology, suggests women exposed to passive smoking up to the age of 12 had an almost five times greater risk of developing breast cancer.
The risk of that disease for women who were exposed to passive smoking, and were also active smokers before age 12, was seven times greater.
Professor Burton said yesterday that based on the findings, the risk of developing breast cancer from tobacco exposure could be the same as for lung cancer – meaning smoking could have caused up to 75 per cent of breast cancer cases.
But his proposition, to be outlined in a paper to the Clinical Oncological Society of Australia's annual scientific meeting in Melbourne, has been strongly rejected by leading breast cancer specialists, who argue that it is not backed by sufficient research and flies in the face of other observations of the disease.
The US study was not designed to directly investigate the link between breast cancer and smoking, and runs counter to a large number of studies that have produced conflicting or inconclusive findings about the potential links.
Three large epidemiological studies are now under way in Victoria aimed at replicating the US findings – which also defy observations that a high proportion of breast cancer cases occur in women from higher socio-economic groups that would not be expected to be exposed to cigarette smoke at high rates.
National Breast Cancer Centre director Sally Redman said the US study would need to be replicated "before we would make any statement about the possibility of links".
Professor Redman said she was concerned that women who had not been exposed to tobacco smoke during childhood and adolescence may be influenced to drop out of mammographic screening programs, which help to detect early cases of breast cancer and give women a greater chance of recovery.
Professor Burton suggests women are more susceptible to the carcinogenic contents of cigarettes during childhood and puberty – when breast cells are rapidly dividing.
Research is finding genetic, environmental and hormonal triggers for the disease.
The COSA meeting heard yesterday that the Australian Breast Cancer Family Study has found the risk of breast cancer in women who have a mutation in the BRCA-1 or BRCA-2 genes increases from 10 to 40 per cent.
"What these women have inherited is a susceptibility for breast cancer, not the certainty of developing breast cancer," Melbourne University professor John Hopper said.
By medical writer BELINDA HICKMAN
24nov99