The addition of pertuzumab to trastuzumab and docetaxel as first-line therapy for women with HER2-positive metastatic breast cancer significantly prolongs progression-free survival (PFS) compared with the use of the 2 agents without pertuzumab, according to results of a new phase 3 clinical trial (Baselga J, et al. N Engl J Med. 2012;366:101-119).
These results from the Clinical Evaluation of Pertuzumab and Trastuzumab (CLEOPATRA) study suggest that using the 2 HER2 inhibitors, trastuzumab and pertuzumab, together provides a complementary activity that enhances HER2 blockade, there-by increasing antitumor activity in patients with HER2-positive breast cancer, as has been demonstrated in earlier studies.
In CLEOPATRA, 808 patients from 25 countries with HER2-positive metastatic breast cancer were randomized to trastuzumab (6 mg/kg every 3 weeks or until progression) plus docetaxel (75 mg/m2) plus either pertuzumab (420 mg every 3 weeks or until progression or unmanageable toxicity) or to placebo. The primary end point was PFS.
The median duration of treatment was 18.1 months in the pertuzumab group and 11.8 months in the placebo group. At approximately 34 months, PFS was 6.1 months longer in the pertuzumab group (18.5 months vs 12.4 months, respectively; P<.001).
In addition, after a median follow-up period of 19.3 months, the objective response rate, a secondary end point, was 80.2% with pertuzumab versus 69.3% with placebo (P = .001).
The rates of grade ≥3 febrile neutropenia and diarrhea were ≥2% higher in the pertuzumab group (13.8% and 7.9%, respectively) than in the placebo group. The rates of cardiac dysfunction did not increase in the pertuzumab group, however.
