Increased occurrence of malignancy before and after chemoradiation for anal squamous cell carcinoma: a multi-institutional analysis

Background Anal squamous cell carcinoma is a rare cancer with increased occurrence of multiple cancers before and after the anal squamous cell carcinoma diagnosis. However, there are limited data on this aspect. This multi-institutional analysis aimed to define the occurrence of malignancies before and after anal squamous cell carcinoma, time trends, and impact on survival and to identify prognostic factors.Methods Initial primary malignancy was defined as a malignancy occurring before the anal squamous cell carcinoma. Second primary malignancy was defined as a distinct primary cancer that developed after anal squamous cell carcinoma diagnosis. Retrospective multi-institutional chart review was done. Progression-free survival (PFS), overall survival, and prognostic factors were evaluated.Results A total of 647 patients with anal squamous cell carcinoma treated with curative intent were analyzed. Median age was 61.2 years with 72% as females. Of these, 150 (23.3%) patients had multiple malignancies with initial primary malignancy in 16% and second primary malignancy in 8%. Patients without prior cancer had better 5-year PFS (81.2% vs 67.2%, P = .011) and overall survival (81% vs 69%, P = .008) compared with those with prior cancer. Second primary malignancies had a statistically significant adverse impact on PFS (hazard ratio [HR] = 4.22) and overall survival (HR = 3.56). Females had better 5-year PFS (82% vs 70%, P = .016) as compared with males. The median time interval for developing anal squamous cell carcinoma (as second primary malignancy) after initial primary malignancy was 9.32 years.Conclusions Anal squamous cell carcinoma patients have an increased risk of multiple malignancies. These patients who have prior cancers have inferior outcomes. Second primary malignancy is a poor prognostic factor in patients with anal cancer. Second primary malignancy can develop years after treatment of primary anal squamous cell carcinoma.