Development of a Predictive Calculator for the Need for Abdominoperineal Resection after Chemoradiation Therapy in...

Chemoradiation therapy (CRT) is standard treatment for anal squamous cell carcinoma (ASCC). Abdominoperineal resection (APR) is usually reserved for patients who are unresponsive to CRT or who have local recurrence. We aimed to identify predictors of the need for an APR.

Case-control analysis from the National Cancer Database (2004 to 2020) of patients with stage I to III ASCC treated with CRT. Patients who underwent APR after CRT were compared with controls who did not undergo surgery post-CRT. Multivariable logistic regression analysis identified predictors of the need for APR. Artificial intelligence large language model generated an R code to develop a predictive online calculator incorporating independent predictors of APR.

A total of 17,067 patients with ASCC (average age 60.2 years; 70% women) were included. APR was performed in 2%. Factors independently associated with an increased likelihood of undergoing APR were male sex (odds ratio [OR] 1.7, p < 0.001), nonspecific keratinizing SCC (OR 1.68, p = 0.011), clinical stage II (OR 1.95, p = 0.032), and stage III disease (OR 2.49, p = 0.003). Conversely, older age (OR 0.977, p = 0.001), Medicare insurance (OR 0.637, p = 0.043), private insurance (OR 0.534, p = 0.001), and larger tumor size (OR 0.999, p = 0.002) were predictive of less need for APR after CRT. The online calculator showed that the predicted probability of needing APR significantly varied.

Significant predictors for the need for APR after CRT for ASCC included age, male sex, advanced clinical stage, specific tumor histology, insurance type, and tumor size. These variables should be considered to help set patient expectations. Follow-up may need to be adjusted in whom these characteristics are identified.