Risk Factors for Colostomy after Chemoradiotherapy in Patients with Squamous Cell Carcinoma of the Anus: A Nationwide, Multicenter Analysis in Japan.

OBJECTIVES

This study investigated the incidence of colostomy, aiming to identify its risk factors following chemoradiotherapy (CRT) for squamous cell carcinoma of the anus (SCCA) in a large Asian cohort, and to clarify the prognostic significance of a complete response (CR). While CRT is the standard of care for SCCA, the risk of colostomy remains a major concern due to its potential impact on a patient's quality of life. Prior studies focused mainly on Western populations, and data from Asian cohorts are limited.

METHODS

We conducted a retrospective multicenter study of 246 patients with SCCA who underwent CRT at 47 Japanese Society for Cancer of the Colon and Rectum (JSCCR)-affiliated institutions-the largest Asian cohort analyzed to date. Colostomy incidence, colostomy-free survival (CFS), and associated risk factors were assessed.

RESULTS

Consistent with earlier Western reports, the 5-year cumulative colostomy incidence was 20.4% and the CFS rate was 65.9%. Multivariable analysis identified tumor size >50 mm (HR 9.619, P=0.0026) and male sex (HR 5.170, P<0.0001) as independent predictors of colostomy. Failure to achieve CR was strongly associated with higher colostomy risk (HR 3.732, P<0.0001), and local recurrence after CR further increased this risk (HR 16.302, P<0.0001).

CONCLUSIONS

In this largest Asian cohort to date of patients with SCCA treated with CRT, tumor size, male sex, and abscence of CR emerged as key predictors of colostomy. Early identification of high-risk patients and achieving CR are essential for improving anal preservation and guiding individualized treatment strategies.