Relationship between prostate-specific antigen bounce body fat distribution and body mass index in permanent seed brachytherapy for prostate cancer

Abstract

PurposeTo analyze the influence of body mass index (BMI) and adipose tissue distribution on prostate-specific antigen (PSA) bounce after iodine-125 prostate brachytherapy. Methods and MaterialsWe studied 20 patients who had PSA bounce (≥0.50ng/mL) after exclusive prostate brachytherapy. These patients were compared with 48 patients without a bounce (<0.50ng/mL). All patients in the comparison group had a followup of ≥24 months and a last PSA ≤0.5ng/mL. Within these 48 patients, there was a group matched for age (n=20). Univariate and multivariate logistic models were estimated to assess the association between age, baseline PSA, prostate volume, D90, visceral fat (VF) volume, and BMI on PSA-bouncing status. ResultsWhen comparing the patients with a bounce to those without, only BMI showed a significantly different distribution (mean, 25.18 vs. 27.47kg/m2; p=0.0342). On a multivariate analysis, BMI had an odds ratio of 0.85 (95% confidence interval, 0.71–0.99, p=0.049), indicating that an increase of 1kg/m2 in BMI is associated with a 15% reduction in the odds of having a bounce. In the univariate analysis with the matching patients, BMI was a significant predictor of a bounce (p=0.0147). In the multivariate conditional logistic model, BMI showed a trend toward an influence on a bounce (p=0.0615). All other factors, including VF, did not have any influence on a PSA bounce. ConclusionsPatients with a lower BMI are more likely to experience a PSA bounce ≥0.50ng/mL. VF did not have an influence on a PSA bounce.