TUESDAY, Aug. 23 (HealthDay News) -- Women at high risk for breast cancer who smoke and drink are less likely to stick with a drug regimen meant to prevent cancer, a new study finds.

Researchers analyzed adherence to the drug tamoxifen by 11,000 women with a high risk of breast cancer who took part in the U.S. National Surgical Adjuvant Breast and Bowel Project's Breast Cancer Prevention Trial.

Heavy drinkers (more than one drink a day) were less likely to stick with the drug regimen after one month. Smokers were less likely to adhere to the medication over the long term.

Yet physical activity levels and obesity were not associated with adherence, suggesting that "poor adherence is not simply based on a pattern of unhealthy behavior in general, but could be related to common sociological, psychological, biological or genetic mechanisms that impact both substance use and medication adherence," the researchers wrote.

The study, published in the current issue of the journal Cancer Prevention Research, also suggests that certain women at high risk for breast cancer may require extra support to help with medication adherence.

"Patients shouldn't be afraid to ask for support from their social network and health care community," lead researcher Stephanie R. Land, a program director and statistician at U.S. National Cancer Institute's Behavioral Research Program, said in a journal news release.

"Health care providers need to know that smokers and drinkers may need additional support. This medication has been shown to prevent breast cancer, but that benefit will only translate if women follow the regimen and maintain it," she added.

More information

The U.S. National Cancer Institute has more on tamoxifen.