The promise of immunotherapy in anal squamous cell carcinoma: a novel approach for an orphan disease.

An estimated 8200 men and women in the United States will receive a diagnosis of squamous cell carcinoma of the anal canal (SCCA) in 2017. Although SCCA is rare, accounting for 2.6% of gastrointestinal cancers, its incidence rate has been steadily increasing over the last few decades in the United States and around the world. More than 90% of cases of SCCA occur in the context of prior human papillomavirus (HPV) infection. To date, preventive vaccinations against HPV remain markedly underutilized. Most patients who have SCCA present with locoregional disease that is cured with chemoradiation. However, metastatic disease develops in 25% of patients. The management of metastatic SCCA is based on single-institutional case series, with no accepted consensus regarding standard of care. Given the complex interplay between the incorporation of HPV DNA into the host cell genome and the oncogenesis of SCCA, immunotherapeutic strategies have become a strong focus of research efforts regarding the management of SCCA. Recently, a phase 2 trial of an anti-programmed death 1 antibody for refractory SCCA has shown positive results. This review summarizes novel immunotherapies that are under active clinical investigation and describes their potential use in the management of metastatic SCCA.