Weekly Paclitaxel/carboplatin/trastuzumab Therapy Improves Pathologic Complete Remission in Aggressive HER2-positive Breast Cancers, Especially in Luminal-B Subtype, Compared with a Once-every-3-weeks Schedule

Background: The efficacy and tolerability of two different schedules of paclitaxel, carboplatin, and trastuzumab (PCarH) for HER2-positive, locally aggressive (stage IIB-IIIC) breast cancers were evaluated in this phase II trial.

Methods: Patients were randomly assigned to receive either weekly (12 doses over 16 weeks) or once-every-3-weeks (4 doses over 12 weeks) treatment. The primary endpoint was pathologic complete remission (pCR) in the breast and axilla. To detect an assumed 35% pCR absolute difference between the two schedules, a minimum of 26 assessable patients in each group was required (two-sided α = 0.05, β = 0.2).

Results: A total of 56 patients were enrolled (weekly group, n = 29; every-3-weeks group, n = 27). In the intent-to-treat analysis, pCR in the breast/axilla were found in 31 patients (55%; 95% confidence interval [CI]: 41%-69%). Compared with the every-3-weeks schedule, the weekly administration achieved higher pCR (41% vs. 69%; p = .03). After adjustment for clinical and pathological factors, the weekly administration was more effective than the every-3-weeks schedule, with hazard ratio of 0.3 (95% CI: 0.1-0.9; p = .03). Interestingly, weekly administration resulted in high pCR rates in both luminal-B (HER2-positive) and ERBB2+ tumors (67% vs. 71%; p = .78), whereas luminal-B (HER2-positive) tumors benefited less from the every-3-weeks schedule compared with the ERBB2+ tumors (21% vs. 62%, p = .03). These results remain after multivariate adjustment, showing weekly administration was more effective in the luminal-B (HER2-positive) subgroup (p = .02) but not in the ERBB2+ subgroup (p = .50).

Conclusion: A more frequent administration might improve the possibility of eradicating invasive cancer in the breast and axilla, especially in the luminal-B (HER2-positive) subtype. Further studies to validate our findings are warranted.