Adding cetuximab to chemoradiation for squamous cell carcinoma of the anal canal is associated with lower incidence of locoregional failure but high toxicity, according to the results of a study published in the Journal of Clinical Oncology (March 2017;35[7]:718-726).
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Squamous cell carcinoma of the anal canal is characterized by high locoregional failure rates after definitive chemoradiation. It is also associated with anogenital human papilloma virus (HPV) infection. Cetuximab has shown in previous studies to enhance the effects of radiation therapy in HPV-associated oropharyngeal squamous cell carcinoma. However, no research has been conducted to analyze the effects of cetuximab in HPV-positive squamous cell carcinoma of the anal canal.
Joseph A Sparano, MD, FACP, Albert Einstein College of Medicine (Bronx, NY), and colleagues conducted a study to analyze the effects of adding cetuximab to chemoradiation for the treatment of locoregional failure in patients with such disease. A total of 61 patients with stage I-III squamous cell carcinoma underwent chemoradiation – including cisplatin, fluorouracil, and radiation therapy – to their primary tumors and regional lymph nodes (45-54 Gy) plus 8 once-weekly doses (1.8 Gy) of concurrent cetuximab. The primary outcome was a 50% reduction in 3-year locoregional failure rate, assuming a 35% rate based on historical data.
Among the 61 patients, 5% had stage I disease, 31% had stage II disease, and 64% had stage III disease. Eighty-nine percent of the patients were HPV positive and 54% of patients had T3 and 4 lesions or positive regional nodes.
Results of the study showed a 3-year locoregional failure rate of 23% by binomial proportional estimate and 21% based on a Kaplan-Meier estimate. After 3 years, progression-free survival was 68% and overall survival was 83%.
Grade 4 toxicities – including diarrhea, neutropenia, nausea, and dehydration, among others – occurred in 32% of the patients. Treatment-related causes accounted for 5% of patient mortalities.
Researchers concluded that although the addition of cetuximab to chemoradiation for squamous cell carcinoma of the anal canal was associated with lower locoregional failure rates compared with chemoradiation alone, resulting toxicities were substantial and locoregional failure still occurred in a significant number of patients. Further studies are needed to find more effective and less toxic therapies. – Zachary Bessette
