Multiple primary malignancies in patients with anal squamous cell carcinoma.

Prior studies examining the risk of second primary malignancy (SPM) after a first primary cancer generally have used large datasets such as the Surveillance, Epidemiology, and End Results (SEER) registry and excluded survivors of previous primaries and developers of synchronous primaries. The goal of this study was to provide a more complete representation of multiple cancer risk in squamous cell carcinoma of the anus (SCCA) patients. A single-institution retrospective study of 46 patients treated definitively for SCCA between January 2006 and July 2017 was conducted. Of the 46 patients, 18 (39%) had either a primary malignancy before SCCA (n=9) or SPM after an index SCCA (n=9). Six patients had ≥3 total malignancies. In our cohort, patients without SPMs tended to die from SCCA recurrence, while patients with SPMs were more likely to die from their SPM than from SCCA. Our study suggests that patients with SCCA are often either survivors of previous cancers or develop later malignancies. Several risk factors may play a role including HPV infection, HPV-related or treatment-related immunosuppression, somatic mutations due to chemotherapy, and genetic factors. Patients with SCCA require lifelong surveillance given their elevated risk of malignancy. Future work should focus on identifying genomic or immunologic factors that may predispose SCCA patients to develop multiple primary malignancies.