Abstract 883: Weight gain is associated with an increased risk of prostate cancer recurrence in the PSA era

Abstract

Abstract Background: Obesity measured at or near time of prostatectomy has been associated with increased risk of prostate cancer recurrence. However, it is unknown whether obesity or weight gain in the years prior to surgery is associated with recurrence. In addition, whether physical inactivity or sedentary behavior exacerbates the obesity-related risk of recurrence has not been studied. Methods: We conducted a retrospective cohort study of men with clinically-localized prostate cancer who underwent radical prostatectomy performed by one surgeon at Johns Hopkins between 1/93 − 3/06 and who previously had not had hormone or radiation therapy. The men were followed for recurrence, defined as PSA recurrence, metastasis, or prostate cancer death. A survey on dietary, lifestyle and medical factors, including weight, height, physical activity, and sedentary behavior 5 years before surgery and 1 year after, was mailed to the men residing in the U.S. as of 11/07. We classified men as normal body mass index (BMI, <25 kg/m2), overweight (25-29.9), or obese (≥30); as physically active (≥5 hrs/wk leisure time activity) or inactive; and as not sedentary or sedentary (≥20 hrs/wk sitting). Men began contributing time at risk starting 1 year after surgery. We used Cox proportional hazards regression to estimate the hazard ratio (HR) of recurrence comparing a gain in BMI of ≥1 kg/m2 from 5 years before surgery to 1 year after with stable BMI, and obesity 1 year after surgery with normal weight. We adjusted for age, race, family history, preoperative PSA, surgery year, positive surgical margins, and pathologic stage and Gleason sum, and for the BMI gain analysis also for BMI 5 years before surgery. For the analysis of obesity 1 year after surgery, we stratified by physical activity and sedentary behavior. Results: At the time of prostatectomy, men who recurred (n=102) were older (58.1 vs. 56.3 yr, p=0.007), more likely to have poorer pathological tumor characteristics (all p<0.0001), and were less likely to have a family history (14.7% vs. 27.7%, p=0.013) than men who did not recur (n=1235). Five years before surgery, 54% were overweight and 9% were obese. Compared with men who had stable BMI, those whose BMI increased ≥1 kg/m2 from 5 years before surgery to 1 year after had twice the recurrence risk (HR=2.18, 95% CI 1.24-3.81). Men who were obese 1 year after surgery were 1.67 times (95% CI 0.91-3.04) more likely to recur compared with men with normal BMI. Risk of recurrence associated with obesity 1 year after surgery was even stronger in men who were sedentary (HR=2.65, 95% CI 1.09-6.47) or inactive (HR=2.30, 95% CI 0.94-5.62). In contrast, in men who were not sedentary (HR=0.89, 95% CI 0.36-2.21) or who were active (HR=1.09, 95% CI 0.45-2.69), obesity 1 year after surgery was not associated with recurrence. Discussion: Weight gain and obesity, especially in sedentary or inactive men, may contribute to risk of prostate cancer recurrence after prostatectomy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 883.