An open-label safety study of lapatinib plus trastuzumab plus paclitaxel in first-line HER2-positive metastatic breast cancer.

BACKGROUND: Recent data support the hypothesis that combining lapatinib and trastuzumab with taxane chemotherapy may offer added clinical benefit to patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). This study examined the safety of the triplet combination in first-line HER2-positive MBC. PATIENTS AND METHODS: Patients were enrolled into three sequential cohorts; the last two cohorts were added by protocol amendment following review of safety data from cohort 1. Patients in cohort 1 received lapatinib (1000 mg/day) plus paclitaxel (80 mg/m(2) per week, 3 of every 4 weeks); cohort 2 received lapatinib (1000 mg/day) plus paclitaxel (70 mg/m(2) per week, 3 of every 4 weeks); and cohort 3 received lapatinib (750 mg/day) plus paclitaxel (80 mg/m(2) per week, 3 of every 4 weeks). All received standard trastuzumab dosing. The primary objective was assessment of dose-limiting toxicities, safety, and tolerability of this combination. RESULTS: The most frequent adverse events (AEs) for all cohorts were diarrhea (89%), rash (79%), fatigue (73%), alopecia (63%), nausea (63%), and vomiting (40%). In cohorts 1 and 2, the incidence of grade 3 diarrhea was 62% and 50%, respectively; in cohort 3, the incidence was 25% (with prophylactic loperamide). Dehydration was the most frequent serious AE (10%). Across cohorts, overall response rate was 75%. CONCLUSIONS: The dose-limiting toxicity of paclitaxel, trastuzumab, and lapatinib in first-line HER2-positive MBC was diarrhea. Of the triplet combinations tested, the cohort receiving 750 mg/day dose of lapatinib had the lowest incidence of diarrhea; therefore, this dose should be used in further studies on the treatment of MBC.

Phase II study evaluating lapatinib in combination with nab-paclitaxel in HER2-overexpressing metastatic breast cancer patients who have received no more than one prior chemotherapeutic regimen.

Lapatinib, an oral, reversible inhibitor of epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2) tyrosine kinase, has proven antitumor activity in HER2-positive metastatic breast cancer (MBC). Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is indicated for the treatment of breast cancer after failure of combination chemotherapy for metastatic disease or relapse within 6 months of adjuvant chemotherapy. This was an open-label, single-arm, multicenter, Phase II study to evaluate the efficacy and safety of nab-paclitaxel plus lapatinib in women with HER2 over-expressing MBC who had received no more than one prior chemotherapeutic regimen. The primary efficacy endpoint was the overall response rate (ORR). This was defined as the percentage of patients having either a complete response (CR) or partial response (PR). Secondary efficacy endpoints included progression-free survival (PFS), overall survival, duration of response (DoR), time to response (TTR), and time to progression (TTP). Investigator-assessed ORR was 53 % (n = 32, 95 % confidence interval (CI): 40.7-66.0) with the majority of patient responses demonstrating a PR (47 %). Four (7 %) patient responses demonstrated a CR, and ten (17 %) a stable disease. The median Kaplan-Meier estimate of investigator-assessed PFS, DoR, TTR, and TTP was 39.7 weeks (95 % CI 34.1-63.9), 48.7 weeks (95 % CI 31.7-57.1), 7.8 weeks (95 % CI 7.4-8.1), and 41 weeks (95 % CI 39.1-64.6), respectively. Lapatinib 1,000 mg with nab-paclitaxel 100 mg/m(2) IV is feasible with manageable and predictable toxicity and an ORR of 53 % comparing favorably with other HER2-based combinations in this setting.