Multicentric neoadjuvant phase II study of panitumumab combined with an anthracycline/taxane-based chemotherapy in operable triple-negative breast cancer: identification of biologically defined signatures predicting treatment impact

Background Triple-negative breast cancer (TNBC) is a heterogeneous group of tumors for some of which the epithelial growth factor receptor (EGFR) pathway may play an important role. We investigated the efficacy and toxicity of an anti-EGFR antibody (panitumumab) combined with a standard neoadjuvant anthracycline–taxane-based chemotherapy in patients with operable, stage II–III, TNBC. Patients and methods Treatment in this multicentric neoadjuvant pilot study consisted of panitumumab (9 mg/kg) for eight cycles q.3 weeks combined with four cycles of 5-fluorouracil, epidoxorubicin and cyclophosphamide (FEC100: 500/100/500 mg/m2) q.3 weeks, followed by four cycles of docetaxel (T: 100 mg/m2) q.3 weeks. Following therapy, all patients underwent surgical resection. Pathologic complete response (pCR) in assessable patients was the main end point while clinical response, toxicity and ancillary studies were secondary end points. Paraffin-embedded and frozen tumor samples were systematically collected with the aim to identify predictive biomarkers of efficacy and resistance in order to select biologically defined subpopulations for potential further clinical development of the anti-EGFR antibody. Results Sixty patients were included with 47 assessable for pathologic response. The pCR rates were 46.8% [95% confidence interval (CI): 32.5% to 61.1%] and 55.3% [95% CI: 41.1% to 69.5%] according, respectively, to Chevallier and Sataloff classifications. The complete clinical response (cCR) rate was 37.5%. Conservative surgery was carried out in 87% of cases. Toxicity was manageable. The association of high EGFR and low cytokeratin 8/18 expression in tumor cells on one hand and high density of CD8+ tumor-infiltrating lymphocytes on the other hand were significantly predictive of pCR. Conclusions Panitumumab in combination with FEC100 followed by docetaxel appears efficacious, with acceptable toxicity, as neoadjuvant therapy of operable TNBC. Several biomarkers could help define large subsets of patients with a high probability of pCR, suggesting a potential interest to further develop this combination in biologically defined subgroups of patients with TNBC. Clinical Trial Number NCT00933517.