PD07-04: Lapatinib vs Trastuzumab in Combination with Standard EC-D Chemotherapy in the Neaodjuvant Treatment of HER2+ Patients. Results from the GEICAM 2006–14 Phase II Randomized Trial.

Background: The addition of trastuzumab (T) to neoadjuvant chemotherapy increases pCR rate in patients with HER2 + breast cancer. Lapatinib (L) in combination with chemotherapy is also an active drug in breast cancer patients. This study investigates the efficacy of trastuzumab or lapatinib added to chemotherapy in the neoadjuvant setting. Methods: Patients (Pt) with tumors greater than 2 cm (or less with positive axilla) and HER2+ (Herceptest 3+ or 2+ with FISH+) that have not received any prior treatment for breast cancer were recruited. Pts were randomized to receive epirubicin 90 mg/m2 plus cyclophosphamide 600 mg/m2 × 4 cycles (cy) followed by docetaxel 100 mg/m2 (with growth colony stimulating factor support) plus either T 8 mg/kg loading dose and then 6 mg/Kg intravenous (EC-DT) or L 1250 mg orally (EC-DL). Patients were stratified according to tumor size (T1-2 vs T3-4), and estrogen receptor status (positive vs negative). The primary end-point was pathological complete response (pCR) in the breast measured by Miller and Payne criteria. Secondary end-points were clinical response (by imaging test), toxicity and correlation between pCR and tumor biomarkers. Results: From February-09 to October-10, 102 pts were randomized (50 EC-DT, 52 EC-DL). Pts characteristics were well balanced between arms. Median age was 48 years (30-79), 56% of pts were premenopausal, 7% grade I, 45% grade III. 14/59/12/15% were T1/T2/T3/T4 and 69% N+. 58% were estrogen receptor positive and 44% progesterone receptor positive. Three patients were FISH negative after central assessment and were not considered evaluable for efficacy. pCR rate in the breast was 52% (95% CI: 38–66) for EC-DT and 25% (95% CI: 13.5−37.5) for EC-DL (p-value=0.0065). pCR—pN0 was 48% (95% CI: 34–62) for EC-DT and 24% (95% CI: 12 - 35) for EC-DL (p-value=0.01). Clinical response was 77% with EC-DT and 65% with EC-DL (p-value=0.176). Grade III-IV toxicity was similar between arms except for diarrhea that was more frequent in EC-DL 14% than in EC-DT 2% (p-value=0.03); more patients discontinue treatment due to toxicity with EC-DL (1 vs 6; p-value=0.055). Conclusions: Our study shows that EC-DT was more efficacious and less toxic than EC-DL in the neoadjuvant treatment of HER2+ pts. Biomarker profiling in the tumors, including activation levels of tyrosine-kinase receptors, signaling pathways and surrogate markers (proliferation and apoptosis) is ongoing; their correlation with pCR will be presented at the meeting. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD07-04.