UCSF

Background

The association of obesity at diagnosis with prostate cancer progression is uncertain. This study aimed to examine the relationship between body mass index (BMI; 18.5-<25, 25-<30, 30-<35, ≥35 kg/m²) and prognostic risk at diagnosis, compare the concordance between prognostic risk assessed at diagnostic biopsy versus pathologic risk assessed at surgery across BMI categories, and investigate the association between obesity and prostate cancer recurrence and all-cause death.

Methods

We examined men enrolled in CaPSURE who underwent radical prostatectomy between 1995 and 2017. Multiple imputation methods were used to handle missing data and reported along with complete case findings.

Results

Participants (n = 5,200) were followed for a median of 4.5 years; 685 experienced recurrence. Obesity was associated with higher prognostic risk at time of diagnosis (OR_obese = 1.5; OR_{very obese} = 1.7) and upward reclassification of disease between biopsy and surgery, driven by change in tumor stage (OR_obese = 1.3; OR_{very obese} = 1.6). We observed an association between BMI and recurrence with adjustment for disease severity using diagnostic factors (HR_{very obese} = 1.7); this association disappeared when adjusting for disease severity factors obtained at surgery.

Conclusions

Our findings suggest that residual confounding may partially explain the conflicting evidence regarding obesity's influence on prostate cancer progression. Assessing T-stage via digital rectal exam may be complicated in larger men, potentially affecting clinical treatment decisions. A strong association with all-cause mortality demonstrates healthier BMI at diagnosis may still improve overall survival.

Impact

Patients with greater BMI are prone to more advanced disease at diagnosis and may be more likely to have their tumor stage underestimated at diagnosis.