Dual HER2 inhibition in combination with anti-VEGF treatment is active in heavily pretreated HER2-positive breast cancer.

BACKGROUND

Preclinical data indicate that dual HER2 inhibition overcomes trastuzumab resistance and that use of an HER2 inhibitor with an anti-angiogenic agent may augment responses.

PATIENTS AND METHODS

We conducted a dose-escalation, phase I study of a combination of trastuzumab, lapatinib and bevacizumab. The subset of patients with metastatic breast cancer was analyzed for safety and response.

RESULTS

Twenty-six patients with metastatic breast cancer (median = 7 prior systemic therapies) (all with prior trastuzumab; 23 with prior lapatinib; one with prior bevacizumab) received treatment on a range of dose levels. The most common treatment-related grade 2 or higher toxicities were diarrhea (n = 11, 42%) and skin rash (n = 2, 8%). The recommended phase 2 dose was determined to be the full Food and Drug Administration (FDA) approved doses for all the three agents (trastuzumab 8 mg/kg loading dose, 6 mg/kg maintenance dose, intravenously every 3 weeks; lapatinib 1250 mg daily, bevacizumab 15 mg/kg intravenously every 3 weeks). The overall rate of stable disease (SD) ≥6 months and partial or complete remission (PR/CR) was 50% (five patients with SD ≥6 months; seven PRs (including one unconfirmed); one CR). The rate of SD ≥6 months/PR/CR was not compromised in patients who had previously received study drugs, those with brain metastases, and patients treated at lower dose levels.

CONCLUSIONS

The combination of trastuzumab, lapatinib and bevacizumab was well-tolerated at maximally approved doses of each drug, and its activity in heavily pretreated patients with metastatic breast cancer suggests that it warrants further investigation.

CLINTRIALSGOV ID

NCT00543504.