The effect of clodronate and antioestrogens on bone loss associated with oestrogen withdrawal in postmenopausal women with breast cancer

In this study we report bone mineral density (BMD) changes during clodronate and antioestrogen treatment in women with breast cancer having discontinued hormone replacement therapy (HRT) at the time of operation compared to women who had not used HRT immediately before the operation. 61 postmenopausal women with operable breast cancer were treated with the adjuvant antioestrogen tamoxifen 20 mg or toremifene 60 mg daily for 3 years. All patients were randomized to clodronate (1.6 g daily orally) or control groups for 3 years. 23 patients had recently (recent users) and 38 never or not for at least 1 year before operation used HRT (non-users). BMD of lumbar spine and femoral neck were measured before antiresorptive therapy (antioestrogens and clodronate) and at 1, 2, 3 and 5 years thereafter. All patients were disease-free at the time of BMD measurements. Patients who had recently used HRT had more significant bone loss as compared to HRT non-users at 3 years in lumbar spine – 3.0% vs. + 1.2% (P< 0.001), but not in femoral neck – 0.4% vs. + 1.7% (P = 0.27). Adding 3-year clodronate treatment to antioestrogen therapy improved BMD marginally at 3 years: lumbar spine + 1.0% vs. –1.7% (P = 0.01) and femoral neck + 2.4% vs. –0.4% (P = 0.12). This was also seen at 5 years of follow-up, 2 years after termination of the antiresorptive therapy: HRT recent users vs. HRT non-users in lumbar spine –6.5% vs. +0.5% (P< 0.0001) and in femoral neck –4.8% vs. –1.5% (P = 0.38); and clodronate vs. controls in lumbar spine –1.0% vs. –3.2% (P = 0.06) and in femoral neck –0.1% vs. –5.2% (P = 0.001, respectively). The type of endocrine therapy (tamoxifen and toremifene) had no significant influence on BMD changes. We conclude from this study that postmenopausal women who have recently discontinued HRT experience more rapid bone loss than HRT non-users. Neither 3-year antioestrogen therapy alone nor antioestrogen together with clodronate could totally prevent the bone loss related to HRT withdrawal in lumbar spine, even though clodronate seemed to retard it. © 2001 Cancer Research Campaign