Coffee Consumption Associated with Increased Mortality of Women with Breast Cancer.

Background: There has been some speculation that caffeine consumption may affect breast cancer. Most case-control studies have not documented evidence of a caffeine-breast cancer incidence link; however, there has been very little analysis of the possible effects of caffeine consumption on breast cancer survival.

Methods: We examined overall a 20-year survival of 96 women treated for breast cancer between 1990 and 1994. As part of their health history, these women were asked about coffee drinking.

Results: Fifty-three women drank one cup a day (79.2% survival), 22 women had two cups a day (72.7% survival), and 21 women drank three or more cups a day (42.9% survival). The effect of coffee consumption on survival was significant (p=0.006, the log rank test). To exclude the effects of lymph node involvement, age at diagnosis, and smoking history, Cox regression was performed. The effect of coffee was significant (p=0.001), independent of the effects of lymph node involvement (p=0.012) and age at diagnosis (p=0.014), and unrelated to a smoking history (p=0.721).

Conclusion: Fatigued breast cancer survivors have an abnormal proinflammatory cytokine activity, an average of 5 years after diagnosis, as well as significant serum cortisol derangements compared to other survivors. One possible interpretation of our results suggests that there is an abnormal hypothalamic-pituitary-adrenal axis functioning in breast cancer patients with persistent fatigue, who might be using coffee to self-medicate. In other words, coffee consumption in the present study might be a surrogate marker for fatigue. Because of the paucity of data regarding caffeine intake, poor sleep, fatigue, and breast cancer survival, further studies could be worthwhile.