(ChemotherapyAdvisor) – Men with nonmetastatic, hormone-sensitive prostate cancer experience the greatest average change in bone mineral density (BMD) during the early treatment period of intermittent androgen deprivation (IAD) and fractures are rare, a study in the Journal of Clinical Oncology online on April 9 concluded.

In this prospective trial of IAD, 100 men with prostate cancer were treated with leuprolide and flutamide for nine months. Androgen deprivation therapy was then stopped until prostate-specific antigen reached a threshold for a new cycle. The threshold was defined as 1ng/mL for radical prostatectomy and 4ng/mL for radiation or primary ADT. The median age at study entry was 64.5 years (range, 49.8–80.9).

Dual-energy x-ray absorptiometry (DXA) scans were performed before starting ADT and subsequently with each change in therapy; at least two consecutive DXA scans were required for analysis. Computed tomography, bone scintigraphy, and lumbar spine x-rays were performed at the beginning and end of each treatment period.

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Of 56 patients who met criteria for analysis, average percentage change in BMD during the first on-treatment period was -3.4% (P<0.001) for the spine and -1.2% (P=0.001) for the left hip. During the first off-treatment period (median, 37.4 weeks; range, 13.4 weeks to 8.7+ years), BMD recovery at the spine was significant, with an average percentage change of +1.4% (P=0.002), the investigators reported. Subsequent periods had heterogeneous changes of BMD without significant average changes. After a median of 5.5 years (range, 1.1 to 13.8+) on trial, one patient (1.8%) had a compression fracture associated with trauma.

“Although the results demonstrated that patients who were treated with IAD experienced a reasonably stable fluctuation in BMD that was slightly below average baseline measurements and did not have an increase in fracture risk, the patient numbers were small,” the wrote. “Fracture risk may be better defined in the Phase 3 cooperative group trial of intermittent vs. continuous therapy in men treated with biochemically recurrent, nonmetastatic disease after treatment with radiation. In our trial, changes in BMD were unpredictable in the individual patient, and hence, continued monitoring with DXA scans is advised.”