Lapatinib plus trastuzumab
The combination of lapatinib and trastuzumab has been evaluated for patients with HER2-positive metastatic breast cancer whose disease progressed while they were being treated with trastuzumab in a phase III trial.[Level of evidence: 1iiA] A total of 291 patients were randomly assigned to treatment with lapatinib alone or in combination with trastuzumab. Compared with lapatinib alone, the combination of lapatinib and trastuzumab significantly improved PFS (HR, 0.74; 95% CI, 0.58-0.94; median, 11 weeks vs. 8 weeks) and OS (HR, 0.74; 95% CI, 0.57-0.97; median, 14 months vs. 10 months). The control arm of lapatinib alone is a nonstandard treatment arm. These data offer heavily pretreated metastatic HER2-positive breast cancer patients an alternative chemotherapy-free treatment regimen using dual HER2 blockade.
Lapatinib plus paclitaxel
A double-blind, randomized phase III study compared paclitaxel and lapatinib with paclitaxel plus placebo as first-line therapy in patients with metastatic breast cancer. In the intention-to-treat population, no benefit was found with the combination treatment. However, specimens were evaluated retrospectively to determine HER2/neu status. When used in HER2/neu-positive patients, treatment with paclitaxel and lapatinib showed improvement in time to progression, event-free survival, response rate, and clinical benefit rate; OS did not increase. Toxicities, specifically alopecia, diarrhea, and rash were higher in the HER2/neu-positive lapatinib group. A series of AE were low and existed in both arms.[Level of evidence: 1iDiii]
Pertuzumab is a humanized, monoclonal antibody that binds to a different epitope at the HER2 extracellular domain than trastuzumab. The binding of pertuzumab to HER2 prevents dimerization with other ligand-activated HER receptors, most notably HER3. Given their potentially complementary mechanisms of action, the phase III CLEOPATRA [NCT00567190] trial assessed the efficacy and safety of pertuzumab plus trastuzumab plus docetaxel versus placebo plus trastuzumab plus docetaxel, in the first-line HER2+ metastatic setting.[Level of evidence: 1iA]. The median PFS was 12.4 months in the control group versus 18.5 months in the pertuzumab group (HR, 0.62; 95% CI, 0.51-0.75; P < .001). Final OS results are pending. The toxicity profile was similar in both treatment groups with no increase in cardiac toxic effects seen in the pertuzumab combination arm.