Phase II trial of gemcitabine/carboplatin (plus trastuzumab in HER2-positive disease) in patients with metastatic breast cancer.

BACKGROUND: Gemcitabine and carboplatin have significant preclinical synergy, and both provide synergistic antitumor activity in metastatic breast cancer (MBC) when used in combination with trastuzumab. The gemcitabine/ cisplatin combination is highly active in MBC with response rates (RRs) of approximately 50% in anthracycline- and taxane-pretreated patients and up to 80% in untreated subjects. This phase II trial studied the efficacy and safety of gemcitabine/carboplatin with or without trastuzumab in patients with MBC.

PATIENTS AND METHODS: Patients were stratified into 3 groups: group 1, HER2-positive; group 2, HER2-negative and taxane- naive/remote (no taxanes within past 2 years); and group 3, HER2-negative and previous taxane therapy. Included were women aged > or = 18 years, Eastern Cooperative Oncology Group performance status of 0-2, with Response Evaluation Criteria in Solid Tumors-defined measurable MBC; HER2-negative or HER2 (3+) by immunohistochemistry or fluorescence in situ hybridization positive. All cycles were repeated every 14 days. On day 1, gemcitabine 1500 mg/m2 over 30 minutes was administered followed by carboplatin area under the curve of 2.5. Group 1 also received trastuzumab 8 mg/kg on day 1 of each cycle followed by 4 mg/kg for every 2 weeks thereafter.

RESULTS: One hundred fifty patients were registered (50, 51, and 49 in groups 1, 2, and 3, respectively). The overall RRs were 64%, 27%, and 32%, respectively, with median time to progression of 7.2, 5.5, and 4.4 months, respectively. Overall, grade 3/4 toxicities included neutropenia (45%), leukopenia (17%), and thrombocytopenia (7%). Alopecia was infrequent: grade 1 (34%) and grade 2 (3%), and there was no significant cardiac toxicity.

CONCLUSION: Gemcitabine/carboplatin/trastuzumab is highly active in patients with HER2-positive MBC. Gemcitabine/carboplatin is active in patients with HER2-negative MBC independent of previous taxane therapy. Gemcitabine/carboplatin with or without trastuzumab administered every 2 weeks is associated with a low frequency of serious toxicity.