Prediagnostic Body-mass Index, Smoking and Prostate Cancer Survival: A Cohort Consortium Study of Over 10,000 White Men with Prostate Cancer.

Few prospective studies have investigated the relationship between pre-diagnostic obesity, smoking and prostate cancer (PCa) survival by timing of measurement, by age at diagnosis, and evaluated the interaction between obesity and smoking.

METHODS: We conducted a multinational survival analysis among 10,106 PCa cases (1,007 PCa deaths and 2,893 total deaths) from eight cohorts with an average of 8.2 years of follow up. Hazard ratio (HR) of PCa death was estimated using Cox proportional hazard model, adjusting for age, alcohol intake, diabetes status, cohort and duration between baseline and diagnosis and subsequently adjusted for tumor stage and grade.

RESULTS: Higher prediagnostic BMI was related to higher risk of PCa death. With each 5 kg/m2 increase in BMI, the multivariate HR for PCa death was 1.08 (95% CI, 1.02-1.14) among overall participants (p-trend = 0.01) and 1.33 (95% CI, 1.18-1.51) among never or former smokers (p-trend < 0.001). This positive trend for PCa mortality was mainly observed among men with BMI measured more than 5 years before diagnosis, and among those age >65 years old at diagnosis. Compared with never smokers, current smokers had significantly elevated risk of PCa death, with a HR of 1.92 (95% CI, 1.52-2.43) regardless of the time of measurement, age at diagnosis and BMI. After further adjusting for tumor stage and grade, the association between BMI, smoking and PCa death was attenuated but remained statistical significant.

CONCLUSIONS: In this consortium study of eight large cohorts, smoking and overweight/obesity before diagnosis were significant predictors for subsequent PCa-specific mortality. Smoking significantly modifies the association of BMI and PCa-specific mortality.