Purpose: To determine whether a matrix metalloproteinase inhibitor improves progression-free survival (PFS) in patients with metastatic breast cancer who have responding or stable disease after first-line chemotherapy.
Patients and methods: One hundred seventy-nine eligible patients were randomly assigned to receive oral marimastat (10 mg bid; n = 114) or a placebo (n = 65) within 3 to 6 weeks of completing six to eight cycles of first-line doxorubicin- and/or taxane-containing chemotherapy for metastatic disease. Patients were evaluated every 3 months until disease progression.
Results: When comparing placebo with marimastat, there was no significant difference in PFS (median, 3.1 months v 4.7 months, respectively; hazard ratio, 1.26; 95% CI, 0.91 to 1.74; P = .16) or overall survival (median, 26.6 months v 24.7 months, respectively; hazard ratio, 1.03; 95% CI, 0.73 to 1.46; P = .86). Patients treated with marimastat were more likely to develop grade 2 or 3 musculoskeletal toxicity (MST), a known complication of the drug indicative of achieving a biologic effect, compared with patients administered placebo (63% v 22%, respectively; P < .0001). Patients with grade 2 or 3 MST had significantly inferior survival compared with patients who had grade 0 or 1 MST (median, 22.5 months v 28.2 months; P = .04). In addition, patients who had a marimastat plasma concentration of at least 10 ng/mL at month 1 and/or 3 were significantly more likely to have grade 2 to 3 MST (P < .0001).
Conclusion: Marimastat does not prolong PFS when used after first-line chemotherapy for metastatic breast cancer. Patients with higher marimastat levels exhibited MST, and MST was associated with inferior survival.