Malignancies diagnosed before and after anal squamous cell carcinomas: A SEER registry analysis

Abstract

Background: Increased risk of a second primary malignancy (SPM) before or after diagnosis of anal squamous cell carcinoma (ASCC) has been reported in a previous single-institution study. We hypothesize that patients diagnosed with ASCC are at increased risk for developing SPMs before or after the diagnosis of ASCC. The primary objective of this study was to identify the diagnoses of cancer most likely to occur as SPMs before or after ASCC.

Methods: This work employs the Surveillance, Epidemiology, and End Results (SEER) Program registry data to conduct a US-population-based study of patients diagnosed with ASCC between 1975 and 2016. In patients diagnosed with ASCC, we evaluated the risk of SPMs and the risk of developing ASCC as an SPM after another cancer using standardized incidence ratios (SIR) for all SPMs by calculating the ratio of observed events in the ASCC cohort compared to expected (O/E) events in a matched reference cohort of the general population.

Results: A total of 7,594 patients with primary ASCC were included. Patients with ASCC were at increased risk of the diagnosis of an SPM (SIR = 1.45), particularly cancers of the lung, vulva, oropharynx, or colon. Patients with ASCC had an increased rate of previous malignancy (SIR = 1.23), especially Kaposi sarcoma or vulvar cancer. Overall elevated incidence of SPMs was unrelated to prior radiation treatment. Radiation treatment was associated with increased risk for SPMs in the female genital system but appeared protective against prostate cancer as SPMs.

Conclusions: Our findings support increased surveillance and screening for second malignancies in patients with these diagnoses, as patients with ASCC are often either survivors of a prior cancer diagnosis or are at increased risk of developing later malignancies.

Keywords: SEER program; anus neoplasms; neoplasms; second primary.

FIGURE 1

Temporal distribution of secondary cancer diagnoses relative to anal squamous cell carcinoma diagnosis. (A) Total number of all observed second primary malignancy cases within 1 year, 1–5 years, 5–10 years, or more than 10 years after first cancer. Blue indicates cases in Cohort 1, diagnosed after an index diagnosis of ASCC, while red indicates cases from Cohort 2 in which ASCC was the second primary malignancy diagnosed after another previous cancer. (B) Rates of SPM diagnoses showing the average number of diagnosed SPM cases per month in ASCC patients with second cancer diagnoses. (C‐D) Number of second primary cases diagnosed following the first diagnosis of ASCC in men and women organized by selected sites of the second primary cancer and timing of diagnosis following ASCC diagnosis. (E‐F) Number of ASCC cases diagnosed as a second primary malignancy in patients with another prior cancer organized by selected sites of first primary and timing of ASCC diagnosis