Validation of JSBMR's CTIBL manual for Japanese men receiving androgen deprivation therapy for prostate cancer.

Introduction: Androgen deprivation therapy (ADT) for prostate cancer causes cancer treatment-induced bone loss (CTIBL), increases the fracture risk 2-3 times, and worsens life prognoses. The Japan Society of Bone and Mineral Research (JSBMR) created a CTIBL treatment manual in 2020; however, no study has validated its use in patients with ADT/CTIBL prostate cancer.

Materials and methods: This study classified 124 patients with prostate cancer without bone metastasis who received ADT into high- and low-risk groups using the JSBMR CTIBL algorithm. Comparisons were made with the period to incident vertebral fracture and the existing International Osteoporosis Foundation (IOF) classification.

Results: The median age was 74 years; the median observation period was 81 months. At 1, 3, 5, 7, and 9 years, the prevalence of incident vertebral fractures was, respectively, 3.3%, 10.7%, 17.9%, 21.4%, and 31.2% in the entire population; 13%, 27%, 36%, 42%, and 58% in the high-risk group (19%); and 1%, 7%, 14%, 17%, and 25% in the low-risk group (81%). The hazard ratio between the two groups was 3.57 (p = 0.0004). Based on multivariate analysis, age, previous vertebral fracture and femoral neck bone density were significant risk factors for incidental vertebral fracture. The JSBMR had a hazard ratio of 3.26 (p = 0.04) relative to 1.13 (p = 0.84) for the IOF, indicating the JSBMR classification performed better.

Conclusion: Taking preventive measures against fractures is necessary, including starting bone-modifying agents early in patients with a high fracture risk. The JSBMR CTIBL manual may be useful for this purpose.