Drinking coffee could decrease the risk of breast cancer recurring in patients taking the widely used drug tamoxifen, according to a recent study. Patients who took the pill, along with two or more cups of coffee daily, reported less than half the rate of cancer recurrence, compared with their non-coffee drinking, tamoxifen-taking counterparts.

A team from Lund University in Sweden followed over 600 breast cancer patients from southern Sweden for an average of five years. Approximately 300 took tamoxifen. The drug, a common hormone therapy after breast cancer surgery, reduces the risk of new tumors by blocking estrogen receptors. How coffee interacts with the treatment, however, isn’t immediately known. The researchers genotyped CYP1A2*1F and CYP2C8*3, which contribute to the metabolism of both tamoxifen and caffeine.

“One theory we are working with is that coffee ‘activates’ tamoxifen and makes it more efficient,” said Maria Simonsson, a doctoral student in oncology at Lund University.

After a median follow-up of 4.92 years, the tamoxifen-treated patients with estrogen-receptor positive tumors who consumed two or more cups each day had a significantly decreased risk for early events compared with patients with low consumption. A high risk for early events was found for patients with low coffee consumption and at least one CYP1A2*1FC or CYP2C8*3 allele.

The Lund University researchers have previously linked coffee consumption to a decreased risk of developing certain types of breast cancer. Caffeine has also been shown to hamper the growth of cancer cells. The latest observational study involving coffee’s role in cancer prevention and treatment underlines the need for more research, according to the team.

“We would like to know more about how lifestyle can interact with breast cancer treatment,” said Helena Jernström, Associate Professor of Experimental Oncology at Lund University. This study was published in Cancer Causes & Control (2013; doi: 10.1007/s10552-013-0169-1). If its results are confirmed, they may warrant new recommendations on coffee consumption during tamoxifen treatment.