Factors affecting bone mineral density in patients with prostate carcinoma before and after orchidectomy

Orchidectomy is an accepted form of androgen-deprivation therapy (ADT) for prostate carcinoma. Osteoporosis is common in elderly individuals and is accelerated by ADT. The authors studied changes in bone mineral density (BMD) after ADT and factors that affected those changes.

Fifty patients with prostatic adenocarcinoma who opted to undergo orchidectomy were studied prospectively. All patients completed 6 months of follow-up, and 20 of those patients completed 12 months of follow-up. Patients' age, weight, height, body mass index (BMI), physical activity, addiction (smoking, alcohol), dietary calcium intake, and lactose tolerance status were noted. Lumbar spinal (L1-L3) trabecular BMD was measured with quantitative computed tomography (QCT) at baseline and every 6 months for 1 year and was compared with preoperative values. The effects of various patient characteristics on preoperative BMD and changes in BMD also were analyzed.

The mean +/- standard deviation (SD) age of the patients was 69.5 +/- 8.1 years, BMI was 23.5 +/- 3.9 kg/m2, dietary calcium intake was 1066.1 +/- 443.3 mg per day. Thirty-eight percent of patients were lactose intolerant. Sixty-two percent of patients were in the light weight-bearing activity group. The mean +/- SD preoperative BMD was 119.2 +/- 34.9 mg/cc, with T-scores of - 1.77 +/- 1.22 and Z-scores of 0.43 +/- 1.27. A decrease in BMD during the first 6 months ( approximately 13%) was statistically significant (P = 0.0001) and continued further during next 6 months (BMD loss of approximately 18% at 12 months). Patients with osteoporosis, as defined by T-scores < or = - 2.5, increased from 24% at baseline to 48% at 6 months. Nonsmokers, nonalcoholics, patients with higher physical activity, and patients with a BMI > 25 kg/m2 had statistically significant higher BMD compared with their counterparts (P < 0.05). Body weight < 60 kg and BMI < 25 kg/m2 were significant risk factors for loss of BMD (P < 0.05). Dietary calcium had a discernible but statistically insignificant effect on BMD (P = 0.16). Lactose intolerance had no significant effect on BMD or bone loss.

Osteoporosis was common in the population affected by prostate carcinoma. Orchidectomy led to accelerated bone loss. Periodic measurement of BMD after ADT would help in the early detection of osteoporosis. Maintenance of high BMI, weight-bearing physical activity, avoidance of alcohol and smoking, and possibly high dietary calcium intake help in maintaining bone mass.