Influence of obesity on tumour volume in patients with prostate cancer

• To investigate the association between body mass index and tumour volume at radical prostatectomy in a large European population.

• Recent data support the hypothesis that the hormonal environment in overweight and obese men may alter androgen-dependent prostate growth. Body mass index (BMI) has been implicated in prostate cancer pathophysiology. • We analysed 1275 patients with prostate cancer who underwent radical prostatectomy at a single tertiary care institution. Mean tumour volume (TV) was evaluated according to BMI WHO categories (normal <25 kg/m(2) vs overweight 25-30 kg/m(2) vs obese 30-35 kg/m(2) vs severely obese >35 kg/m(2)). • Univariable linear regression analyses targeted the association between BMI and TV at radical prostatectomy. Multivariable analyses were adjusted for age, prostate-specific antigen value, biopsy Gleason sum, clinical stage and prostate volume.

• Mean BMI was 26.3 kg/m(2) (median 26; range 16.7-42.0). Mean TV was 5.6 mL (median 3.3; range 0.1-61.2). The mean prostate-specific antigen value was 10.3 ng/dL (median 6.6; range 0.3-327). • The mean TV was 5.0, 5.8, 6.3 and 9.2 mL in normal, overweight, obese and severely obese patients, respectively (P= 0.03). TVs in men with a normal BMI were 84% smaller than in severely obese men (5.0 vs 9.2 mL). • On univariable analysis, BMI was correlated with TV at radical prostatectomy (P < 0.001). On multivariable analysis, BMI reached the independent predictor status after adjustment for age, prostate-specific antigen value, biopsy Gleason score, clinical stage and prostate volume (P= 0.03).

• We showed that BMI is independently associated with prostate cancer volume at radical prostatectomy. The present results confirm that obesity may play a key role in prostate cancer pathophysiology.