Scientists at Lund University in Sweden found patients who took Tamoxifen, along with two or more cups of coffee daily, reported less than half the rate of cancer recurrence, compared with their Tamoxifen-taking counterparts who drank one cup or less.
The team 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 tumours by blocking oestrogen receptors. How coffee interacts with the treatment, however, isn't immediately known.
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 Jernstrom, Associate Professor of Experimental Oncology at Lund University.