(S004) Combination of Radiotherapy and Cetuximab for Aggressive, High-Risk Cutaneous Squamous Cell Cancer of the Head and Neck: A Propensity Score Analysis

Joshua D. Palmer, MD, Jon Strasser, MD, Michael Dzeda, MD, Neil Hockstein, MD, Charles Schneider, MD, Adam Raben, MD; Sidney Kimmel Medical College of Thomas Jefferson University; Helen F. Graham Cancer Center of Christiana Care Health System

BACKGROUND: Locally advanced, high-risk cutaneous squamous cell carcinoma (CSCC) of the head and neck is typically aggressive and treated with combined modality therapy. These patients tend to be older and frail, with multiple comorbidities, which makes chemotherapy difficult to tolerate. Cetuximab is a monoclonal antibody against the epidermal growth factor (EGF) receptor and has demonstrated activity in CSCC. We investigate the safety and preliminary efficacy of combined therapy in advanced, high-risk CSCC with the addition of cetuximab.

METHODS: Patients who were identified with locally advanced CSCC with high-risk or very-high-risk features were treated with cetuximab and radiotherapy between 2006 and 2013. A matched cohort over the same time period was identified that was treated with radiation. Propensity score analysis was performed with weighted factors, including Charlson comorbidity index score (age-adjusted), age, Karnofsky performance status (KPS), primary location, T and N stage, recurrent status, margin status, lymphovascular space invasion (LVSI), perineural invasion (PNI), and grade. Overall survival (OS), progression-free survival, and freedom from local or distant recurrence were evaluated with the Kaplan-Meier method for both the unadjusted and propensity score-adjusted groups. Multivariate analysis was performed using Cox proportional hazard models.

RESULTS: A total of 29 patients were in the cetuximab group, and 39 were in the control group. Median follow-up for living patients was 30 months. Patients in the cetuximab group were more likely to have advanced N stage, positive margins, and recurrent disease. After matching of propensity scores, the groups were well balanced. OS was not statistically significantly different between the two groups, but there were approximately 20% more long-term survivors in the cetuximab group after matching, with 80% vs 61% surviving at 4 years. Local control rate was 76% and 79% in the cetuximab and control groups, respectively. The rate of distant metastases was lower in the cetuximab group (6.8% vs 10%). The incidence of grade 2–3 toxicity was 41% in the cetuximab group. There was one grade 3 toxicity (cetuximab-induced acneiform rash), one grade 4 toxicity (dysphagia), and no grade 5 toxicity.

CONCLUSIONS: Although limited by small numbers, we found that there were more long-term survivors and less distant metastasis in the cetuximab group. This is the largest report of CSCC patients treated with cetuximab. In the absence of prospective data, we believe that these data reveal that the addition of cetuximab is well tolerated and reveal signs of efficacy in this typically poorly performing group of patients and should be pursued in clinical trials.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org