High BMI, Weight Gain Tied to Increased Mortality in Prostate Cancer

Alyssa N. Troeschel, MPH

Obese men with nonmetastatic prostate cancer have higher cardiovascular disease—related mortality and all-cause mortality, and potentially increased prostate cancer–specific mortality, according to findings published in the Journal of Clinical Oncology.

In the study, the distribution of 3855 patient deaths from all causes revealed 500 disease—specific deaths and 1155 cardiovascular disease–related deaths. Men who had an obese body mass index (BMI) ≥30 kg/m² were more likely to experience prostate cancer—specific mortality versus men who had a healthy BMI of 18.5 < 25.0 kg/m² (HR, 1.28; 95% CI, 0.96-1.67). Cardiovascular disease—related mortality was also heightened among obese men versus men at healthy weight (HR, 1.24; 95% CI, 1.03-1.49), translating to worse all-cause mortality (HR, 1.23; 95% CI, 1.11-1.35).

Moreover, men who gained >5% of their weight after diagnosis had a higher risk of prostate cancer—specific mortality versus those who maintained stable weight (+/- <3%; HR, 1.65; 95% CI, 1.21-2.25). This also translated into worse all-cause mortality among men who gained >5% of their body weight after diagnosis versus those who maintained stable weight (HR, 1.27; 95% CI, 1.12-1.45).

Men who were overweight at diagnosis and developed an obese BMI after diagnosis had a higher likelihood of prostate cancer—specific mortality (HR, 1.69; 95% CI, 1.12-2.57).

"Our results suggest that among survivors of nonmetastatic prostate cancer, postdiagnosis obesity may be associated with higher cardiovascular disease—related mortality and all-cause mortality," Alyssa N. Troeschel, MPH, and PhD candidate at Emory University, and coinvestigators wrote. "Postdiagnosis weight gain may be associated with a higher mortality as a result of all causes and prostate cancer," Troeschel and coinvestigators added.

In the analysis, men in the Cancer Prevention Study II Nutrition Cohort who were diagnosed with nonmetastatic prostate cancer between 1992 and 2013 were followed for mortality through 2016. Men who died within 4 years of follow-up were excluded from the analysis.

Patients' "baseline" BMI was taken from the first survey they completed within the first 6 years after diagnosis (n = 8330). Patients completed follow-up questionnaires every 2 years thereafter to track their change in weight (n = 6942).

Prostate cancer—specific mortality served as the primary endpoint of the trial. Key secondary endpoints included cardiovascular disease–related mortality and all-cause mortality.

The multivariable models used to calculate the association between BMI and mortality controlled for age, education, smoking status, physical activity, American Joint Committee on Cancer primary tumor category, Gleason score, initial treatment, and year of diagnosis. The weight change models also adjusted for patients’ postdiagnosis BMI in the calculation.

In the BMI cohort, 36% of men were of healthy weight, 49% were overweight, and 16% were determined to be obese.

Although the mortality rate was most pronounced in obese men, overweight men also demonstrated a higher risk of prostate cancer—specific mortality (HR, 1.23; 95% CI, 1.00-1.50), but not cardiovascular disease–related mortality or all-cause mortality.

"Survivors of prostate cancer are advised to maintain a healthy weight and avoid weight gain, and our findings provide additional evidence to follow these recommendations," Troeschel and coinvestigators wrote.

Notably, obesity was associated with a higher likelihood of prostate cancer—specific mortality in men with low-risk tumors (HR, 1.58; 95% CI, 1.13-2.22) but not high-risk tumors (HR, 1.00; 95% CI, 0.63-1.58). Although the relationship between BMI and prostate cancer–specific mortality was stronger in men with low-risk tumors, the association between risk category and BMI was not statistically significant (P = .63).

In the weight change cohort, all-cause mortality was also heightened in men who lost 3% to 5% of their body weight (HR, 1.15; 95% CI, 1.02-1.31) and in men who lost >5% of their body weight (HR, 1.30; 95% CI, 1.16-1.46). There was no association between weight change and cardiovascular disease—related mortality.

Additional analyses that accounted for other potential confounding variables, such as treatment course, revealed similar findings.

"Future studies are needed to determine whether intentional weight loss provides health benefits among overweight and obese survivors of prostate cancer. Clinicians should be vigilant about identifying moderate weight loss or gain in survivors of prostate cancer because both have poor prognostic implications," Troeschel and coinvestigators concluded.

Postdiagnosis body mass index, weight change, and mortality from prostate cancer, cardiovascular disease, and all causes among survivors of nonmetastatic prostate cancer [published online ahead of print April 6, 2020]. J Clin Oncol. doi: 10.1200/JCO.19.02185