Post-diagnostic coffee and tea consumption and risk of prostate cancer progression by smoking history

Post-diagnostic coffee and tea consumption and prostate cancer progression is understudied.

We examined 1,557 men from the Cancer of the Prostate Strategic Urologic Research Endeavor who completed a food frequency questionnaire a median of 28 months post-diagnosis. We estimated associations between post-diagnostic coffee (total, caffeinated, decaffeinated) and tea (total, non-herbal, herbal) and risk of prostate cancer progression (recurrence, secondary treatment, bone metastases, or prostate cancer death) using Cox proportional hazards regression. We also examined whether smoking (current, former, never) modified these associations.

We observed 167 progression events (median follow-up 9 years). Higher coffee intake was associated with higher risk of progression among current smokers (n = 95). The hazard ratio (HR) [95% confidence interval (CI)] for 5 vs 0 cups/day of coffee was 0.5 (CI 0.2, 1.7) among never smokers, but 4.5 (CI 1.1, 19.4) among current smokers (p-interaction: 0.001). There was no association between total coffee intake and prostate cancer progression among never and former smokers. However, we observed an inverse association between decaffeinated coffee (cups/days) and risk of prostate cancer progression in these men (HR _{> 0 to  < 1 vs 0}: 1.1 (CI 0.7, 1.8); HR_{1 to <2 vs 0}: 0.7 (CI 0.3, 1.4); HR_{≥2 vs 0}: 0.6 (CI 0.3, 1.1); p-trend = 0.03). There was no association between tea and prostate cancer progression, overall or by smoking status.

Among non-smoking men diagnosed with localized prostate cancer, moderate coffee and tea consumption was not associated with risk of cancer progression. However, post-diagnostic coffee intake was associated with increased risk of progression among current smokers.