Safety and Efficacy of Panitumumab (pmab) in HPV Positive (+) and HPV Negative (-) Recurrent/metastatic (R/M) Squamous Cell Carcinoma of the Head and Neck (SCCHN): Analysis of the Phase 3 SPECTRUM Trial

Background: Pmab is a fully human monoclonal antibody against the epidermal growth factor receptor. SPECTRUM (ClinicalTrials.gov Identifier: NCT00460265; Sponsor: Amgen) evaluated the safety and efficacy of pmab + platinum-based chemotherapy (CT) vs CT in patients (pts) with R/M SCCHN. This prespecified analysis presents outcomes by tumor HPV status. Methods: All tumor samples were centrally reviewed. HPV status was determined using a validated immunohistochemistry assay to p16INK4A by an independent laboratory blinded to treatment assignments. Tumor samples were scored positive, negative, or failed according to prespecified guidelines. (Table presented) Results: A total of 657 pts were enrolled (ITT). As of August 2011, 377 pts (57%) had samples with >10% viable tumor on central review and were evaluable for HPV testing. The assay failure rate was <1%. Eighty-three (22%) tumors were HPV+ and 294 (78%) were HPV-. HPV+ rates varied by tumor site (36% oropharynx, 19% larynx, 16% oral cavity, and 13% hypopharynx) and by geographic region (42% N America, 22% W Europe, 20% Asia Pacific, 19% E Europe, and 17% S America). Demographics were generally balanced except that pts with HPV+ vs HPV- tumors were more frequently non-smokers (30% vs 14%), had oropharyngeal primary tumors (45% vs 23%), and had more poorly differentiated tumors (31% vs 15%). Efficacy results are shown in the table. Adverse events (AEs) grade 3+ (pmab + CT vs CT) were 86% vs 87% for HPV+ and 86% and 77% for HPV-. Serious AEs (pmab + CT vs CT) were 51% vs 32% for HPV+ and 53% and 41% for HPV-. Conclusions: The addition of pmab to CT improved overall survival and progression-free survival in pts with HPV- R/M SCCHN. There was no incremental benefit in pts with HPV+ tumors. These findings should be evaluated in additional studies.