EP397 - Treatment Patterns and Survival Outcomes in Rectal and Anal Squamous Cell Carcinoma: An NCDB Analysis

Sunday, May 10, 2026

1:13 PM - 1:18 PM ET

ePoster Presenter(s)

Hannah Chay, BA (she/her/hers)

Medical Student
University of California, San Francisco
University of California, San Francisco
San Francisco, CA, United States

Disclosure information not submitted.

Author(s)

LF

Laleh Foroutani, MD

Postdoctoral Research Fellow
University of California, San Francisco
San Francisco, CA, California, United States

Disclosure information not submitted.
Saffanat Sumra, BA (she/her/hers)

Medical Student
University of California, San Francisco
University of California, San Francisco
San Francisco, CA, United States

Disclosure information not submitted.

Senior Author(s)

B. Mark Zhao, University of California, San Francisco

Assistant Professor of Clinical Surgery
University of California, San Francisco
San Francisco, CA, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.

All of the relevant financial relationships listed below have been mitigated.

B. Mark Zhao, University of California, San Francisco: This individual has no financial relationships with ineligible companies.

Purpose/Background: Colorectal cancer is the third most common malignancy and a leading cause of cancer-related mortality, with adenocarcinoma as the predominant histology. In contrast, squamous cell carcinomas (SCC) are rare. While definitive chemoradiation is guideline-concordant care for anal SCC (ASCC), the optimal management of rectal squamous cell carcinoma (RSCC) remains uncertain. This study aims to characterize contemporary, real-world treatment patterns for patients with ASCC and RSCC.

Methods/Interventions: Using the National Cancer Database, we retrospectively analyzed adults with non-metastatic ASCC or RSCC diagnosed between 2010-2022. Patients were categorized into seven treatment groups: 1) definitive chemoradiation (CRT); 2) neoadjuvant CRT + radical surgery (nCRT-RS); 3) radical surgery + additional therapy (RS-AT), where AT included chemotherapy, radiation, or CRT; 4) radical surgery alone (RS); 5) local excision + additional therapy (LE-AT); 6) local excision alone (LE); and 7) chemotherapy alone. Overall survival (OS) was estimated using Kaplan-Meier and compared with multivariable Cox regression with backward stepwise selection. Candidate covariates included age, sex, race, ethnicity, insurance status, facility type, Charlson-Deyo Comorbidity Score (CDCC), grade, clinical stage, and treatment group.

Results/Outcomes: Among 97,624 patients, 87,248 (89.4%) had ASCC and 10,376 (10.6%) had RSCC. The most common treatment was definitive CRT for both ASCC (60.3%) and RSCC (56.7%). The second most common treatment differed by site, with LE-AT for ASCC (17%) and chemotherapy alone for RSCC (22.4%). OS varied significantly by treatment in both cohorts (log-rank p< 0.0001). In ASCC, LE-AT was associated with the longest unadjusted survival and improved outcomes on multivariable analysis (HR 0.87, p< 0.0001), while all other strategies were associated with inferior survival compared to definitive CRT (p < 0.0001). In RSCC, no approach outperformed definitive CRT. Worse survival was observed with nCRT-RS (HR 1.46), RS-AT (HR 2.15), LE (HR 1.35), and chemotherapy alone (HR 2.10) (all p< 0.05).

Conclusion/Discussion: Despite anatomical differences, both ASCC and RSCC are predominantly managed with definitive CRT. In ASCC, LE-AT was associated with improved survival, likely reflecting favorable selection of small, early-stage tumors amenable to LE. Moreover, the location of tumors of the anus may also influence treatment efficacy as local excision is often only performed on tumors of the perianal skin. In RSCC, no strategy outperformed definitive CRT, including surgical resection. Furthermore, the frequent use of chemotherapy alone in RSCC highlights practice heterogeneity in the absence of clear evidence. These findings underscore the need for evidence-based strategies in rare cancers such as RSCC.

Kaplan-Meier Overall Survival Curves for Anal (A) and Rectal (B) Squamous Cell Carcinoma, Stratified by Anatomic Site

Patients were categorized into seven treatment groups: definitive chemoradiation (CRT), neoadjuvant CRT + radical surgery (nCRT-RS), radical surgery + additional therapy (RS-AT), radical surgery alone (RS), local excision + additional therapy (LE-AT), local excision alone (LE), and chemotherapy alone. Overall survival differed significantly by treatment in both cohorts (log-rank p < 0.0001).