Randomized trial of low- versus high-dose medroxyprogesterone acetate in the induction treatment of postmenopausal patients with advanced breast cancer.

In a randomized trial, 210 postmenopausal women with advanced measurable breast cancer were allocated to two different schedules of medroxyprogesterone acetate (MPA). In the induction phase they received either 1,000 mg intramuscular (IM) MPA (high dose) daily or 500 mg IM MPA (low dose) twice weekly for four weeks. The maintenance treatment consisted of 500 mg MPA IM once weekly for all patients. In total, 184 patients were considered evaluable. The response rate was significantly higher (p = 0.004) for patients receiving high-dose MPA (30 [33%] of 91) as compared to the women receiving the low-dose regimen (14 [15%] of 93) and was consistent across all prognostic subgroups. These prognostic subgroups included soft-tissue and osseous metastases, two metastatic sites, patients greater than 60 years, disease-free interval greater than 60 months, no prior chemotherapy, patients with a response to the last hormonal treatment before MPA, unknown estrogen receptors, and positive progestin receptors. The two different schedules of MPA did not influence the time to progression and the survival. Toxicity was similar in both regimens. These results confirm that a higher response rate can be achieved with a more intensive MPA schedule. This treatment may represent an ideal second-line choice in the endocrine therapy of advanced breast cancer; however, its role as a first-line treatment remains to be defined.