Obesity is associated with a lower risk of death among men with non-metastatic castration-resistant prostate cancer (CRPC), new study findings suggest.
Using the Shared Equal Access Regional Cancer Hospital database, first author Adriana C. Vidal, MD, of Cedars-Sinai Medical Center in Los Angeles, and colleagues identified 1192 men with non-metastatic CRPC. Of these, 438 (37%), 464 (39%), 239 (25%), and 51 (4%) were obese, overweight, normal weight, and underweight, respectively. In adjusted analyses, each 1 kg/m2 increment in body mass index was associated with a statistically significant 2% decreased risk of all-cause mortality. Obesity was associated with a statistically significant 21% decreased risk of all-cause mortality compared with normal weight (reference), the investigators reported online ahead of print in BJU International. Obesity was not associated with the risk of prostate cancer (PCa)-specific mortality or metastasis.
The investigators defined obesity, overweight, normal weight, and underweight as a BMI (in kg/m2) of 30 or higher, 25–29.9, 21–24.9, and less than 21, respectively. During follow-up, metastases developed in 686 patients, 848 died, and 548 died from PCa. The median follow-up time among patients who were alive during the study was 34 months.
The authors noted that it is well established that obesity is associated with aggressive PCa and worse long-term outcomes among men with localized PCa, and a few studies have evaluated the link between BMI and PCa outcomes among men with metastatic CRPC. The current study, led by Stephen J. Freedland, MD, of Cedars-Sinai, is the first to investigate PCa outcomes among patients with non-metastatic CRPC.
The investigators said their data suggest that obesity may be unrelated to PCa aggressiveness and progression in men with non-metastatic CPRC, but, overall, is a favorable prognostic sign. In a discussion of possible explanations for their findings, the authors noted that while tumor-related cachexia is unlikely among patients with non-metastatic CRPC, patients might have cachexia from other causes such as heart disease, chronic obstructive pulmonary disease, and/or other types of cancer. “Thus, a greater BMI may demonstrate a current lack of cachexia but also perhaps provide some protection from future cachexia, allowing patients to live longer.”
Dr Vidal and her colleagues pointed out that they observed that the risks of all-cause and cancer-specific mortality, although not statistically significant, were greatest among underweight patients compared with normal weight men, “arguing this could be in part cachexia-related.”
Study strengths include the large number of men with non-metastatic CRPC and PCa events, “which allowed us to both stratify analysis by BMI categories and adjust for clinicopathological features.” With regard to study limitations, the authors pointed out that they lacked data on additional treatments after CPRC diagnosis as well as data reflecting changes in nutritional and lifestyle regiments prior to CRPC.
Vidal AC, Howard LE, de Hoedt A, et al. Obese patients with castration-resistant prostate cancer may be at a lower risk of all-cause mortality: results from the Shared Equal Access Regional Cancer Hospital (SEARCH) database. BJU Int. 2018; published online ahead of print.