Outcomes with anti-EGFR monoclonal antibodies in metastatic and recurrent anal squamous cell carcinoma

Objectives: Metastatic squamous cell carcinoma anal cancer (SCCA) is rare. Prospective data recommends front-line platinum doublet combinations and second-line anti-programmed death-1 therapy. Standard therapy beyond these treatments are currently unknown. We evaluated anti-EGFR monoclonal antibody (mAb) outcomes in metastatic SCCA. Methods: Metastatic SCCA patients given anti-EGFR mAb from Oct 2011-May 2018 were included. Primary endpoints included best response, progression-free survival, and overall survival. Results: 56 patients were evaluated with a median of one prior therapy. Most patients (~90%) received anti-EGFR mAbs with chemotherapy. Response rate (any response) was 41%. Median PFS was 4.3 months with a median OS of 16 M. Seven patients with disease control proceeded onto maintenance therapy (anti-EGFR mAb ± a fluoropyrimidine) with a median PFS of 13.8 M. Next generation sequencing of 16 pts (28%) showed 4 pts had a PIK3CA mutation with 3 of these 4 patients demonstrating progression on initial restaging. Conclusion: Our analysis suggests anti-EGFR mAb therapy with chemotherapy provides clinical benefit in previously treated metastatic SCCA. Our maintenance therapy and the role of PIK3CA MT outcomes were thought-provoking. Expert Opinion: Metastatic SCCA patients have limited options; therefore, anti-EGFR mAbs may provide benefit in the treatment armamentarium and should be further explored.