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Mount Sinai Hospital, Toronto, ON, Canada.
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Editor’s note: Numerous studies have shown that the risk of developing asynchronous contralateral breast cancer, a primary breast cancer occurring in the opposite breast subsequent to a first breast cancer diagnosis, in female survivors of breast cancer is fivefold higher than the risk of developing a first primary breast cancer in unaffected women. It is reasonable to assume that women who go on to develop asynchronous contralateral breast cancer have an even higher prevalence of risk factors than those who develop only one tumor, although there may be mitigating factors such as the treatment received for the first breast cancer. Few studies have examined the role of alcohol intake or cigarette smoking, two potentially modifiable risk factors, in this context. There are now a number of meta-analyses confirming that alcohol is a risk factor for both pre- and postmenopausal first primary breast cancer; however, thus far, no significant association between alcohol intake and second primary breast cancer has been observed. Cigarette smoking is more controversial as a risk factor for breast cancer, with inconsistent published data.