Obesity is associated with risk of progression for low-risk prostate cancers managed expectantly.
BACKGROUND
Active surveillance (AS) is an expectant management strategy for prostate cancer (PCa). The impact of obesity on progression is not well characterized in this population.


OBJECTIVE
To determine if obesity is associated with progression in men on AS for low-risk PCa.


DESIGN, SETTING, AND PARTICIPANTS
Men undergoing AS for low-risk PCa (no Gleason pattern ≥4, three or fewer cores involved or one-third or less of the total number of cores involved, and no core with >50% cancer involvement) were identified at our institution.


OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS
The outcomes were pathologic progression (defined as no longer meeting low-risk criteria on follow-up biopsy) and therapeutic progression (defined as intent to initiate active treatment). Kaplan-Meier curves and multivariable logistic regression and Cox proportional hazards models were used, with separate models for reclassification at confirmatory biopsy (first biopsy after diagnostic biopsy) and progression beyond confirmatory biopsy.


RESULTS AND LIMITATIONS
In this cohort of 565 men (median follow-up: 48 mo), 124 (22%) were obese (body mass index [BMI] ≥30kg/m(2)). Pathologic and therapeutic progression occurred in 168 men (30%) and 172 men (30%), respectively. No association was noted between obesity and risk of progression at the confirmatory biopsy. However, beyond confirmatory biopsy, obesity was associated with a greater probability of pathologic progression (p=0.007) and therapeutic progression (p=0.007) in Kaplan-Meier analyses. In adjusted Cox models, each 5-unit increase in BMI was associated with an increased risk of pathologic progression (hazard ratio [HR]: 1.5; 95% confidence interval [CI], 1.1-2.1; p=0.02) and therapeutic progression (HR: 1.4; 95% CI, 1.0-1.9; p=0.05). The main limitation is the retrospective design, limiting the ability to assess BMI changes over time.


CONCLUSIONS
Obesity was associated with a significantly increased risk of progression beyond the confirmatory biopsy. This suggests an increased risk of long-term biologic progression rather than solely misclassification.


PATIENT SUMMARY
As opposed to immediate active treatment (surgery or radiation), active surveillance (AS) involves closely monitoring low-risk prostate cancers and only using active treatment if there are signs of progression. Our study is the first to suggest that obesity is associated with a higher risk of cancer progression while on AS. Further research is needed to determine if diet and exercise can decrease the risk of cancer progression while on AS.