Carboplatin activity in untreated metastatic breast cancer patients--results of a phase II study

Due to the favourable results previously obtained with cisplatin in breast cancer (54% response rate), we studied a second-generation platinum analogue, carboplatin, in patients with previously untreated breast cancer. A total of 20 patients were entered in the study and all were evaluable. The median age was 57 years and all patients were in menopause. Karnofsky scores of 80-100 and 40-70 were registered in 14 and 6 cases, respectively. The predominant metastatic site was soft tissue in 12 subjects, visceral organs in 5 and bone in 3; 14 patients had greater than 2 metastatic sites. Carboplatin was given i.v. at a dose of 400 mg/m2 on day 1, with a 3-week rest period. In 13 patients who did not respond or whose disease recurred after carboplatin treatment, the CMFVP, CAP or FAC regimen was given as second line treatment. Carboplatin activity was observed in 4 patients [2 complete remissions (CRs) and 2 partial responses (PRs)], for a response rate of 20% (4/20); the 2 PRs were observed in soft tissue and bone and the 2 CRs, in lung, liver and bone. Remission lasted 2-10 months (mean, 4 months). CMFVP given as second-line chemotherapy to 13 patients produced 7 PRs (7/13, 54%). Toxicity was moderate, producing no drug-related deaths. Anemia (grade I-II) was recorded in seven patients; grade I-II leukopenia, in six; and grade III-IV leukopenia in two (median leukocyte nadir, 1,600/mm3). Thrombocytopenia was observed in three cases (grades I, II and III; median platelet nadir, 47,800/mm3). Unpleasant nausea/vomiting was pronounced (12 cases of grade III-IV) in 19 subjects. There were no cases of neuro- or nephrotoxicity. Due to permanent myelosuppression, no more than five cycles could be given. Our study showed that, unlike cisplatin, carboplatin given at a dose of 400 mg/m2 has low antitumorigenic activity in breast cancer patients and produces pronounced myelotoxicity. Additional first-line chemotherapy studies using carboplatin are needed to define the antitumorigenic activity of this platinum analogue.