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. 2021 Apr;12(2):831-844.
doi: 10.21037/jgo-20-530.

A population-based analysis of chemoradiation versus radiation alone in the definitive treatment of patients with stage I-II squamous cell carcinoma of the anus

Jacob S Parzen  1 , Aleksander Vayntraub  1 , Bryan Squires  1 , Muayad F Almahariq  1 , Andrew B Thompson  1 , John M Robertson  1 , Peyman Kabolizadeh  1 , Thomas J Quinn  1
Affiliations

A population-based analysis of chemoradiation versus radiation alone in the definitive treatment of patients with stage I-II squamous cell carcinoma of the anus

Jacob S Parzen et al. J Gastrointest Oncol. 2021 Apr.

Abstract

Background: The optimal management of patients with stage I-II squamous cell carcinoma (SCC) of the anus is controversial. The current study evaluates the efficacy of combined chemotherapy and radiation therapy (CRT) versus radiation therapy (RT) alone in the treatment of these patients using the Surveillance, Epidemiology, and End Results (SEER) registries.

Methods: SEER 18 Custom Data registries were queried for patients with stage I-II SCC of the anus. Univariate analysis (UVA) and multivariable analysis (MVA) using Kaplan-Meier and Cox proportional hazards regression modeling were performed. Propensity-score matched analysis with inverse probability of treatment weighting (IPTW) was used to account for indication bias.

Results: A total of 4,288 patients with stage I-II disease were identified, of whom 3,982 (93%) underwent CRT and 306 (7%) underwent RT. Median follow-up was 42 months. Approximately 30.8% had T1 disease and 69.2% had T2-T3 disease. The IPTW-adjusted 5-year overall survival (OS) was 76.7%, with no significant differences between the CRT and RT groups (77% vs. 73.5%, P=0.33). On multivariate IPTW-adjusted analysis, the lack of association between CRT use and OS was upheld (HR, 0.84, 95% CI, 0.65-1.08, P=0.2). On subgroup analyses, 5-year OS was 86% with CRT (n=1,216) and 84.2% with RT (n=103) (P=0.74) in stage I (T1N0) patients, while 5-year OS was 72.8% with CRT (n=2,766) and 66.4% with RT (n=203) (P=0.13) in stage II (T2-3N0) patients. CRT was associated with improved median OS in stage II patients (119 months vs. not reached, P=0.04).

Conclusions: The current study suggests that omission of concurrent chemotherapy is not associated with inferior OS in patients with stage I SCC of the anus. However, combined chemoradiation was superior to radiation alone in patients with stage II disease. Prospective evidence is needed to optimize clinical decision-making in this patient population.

Keywords: Squamous cell carcinoma of anus; chemoradiation; population-based study; radiation monotherapy.

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at: http://dx.doi.org/10.21037/jgo-20-530). The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
CONSORT diagram demonstrating the inclusion and exclusion criteria used to select stage I–II squamous cell carcinoma (SCC) of the anus.
Figure 2
Figure 2
Overall survival curves for stage I–II SCC of the anus for the unadjusted groups (A) and IPTW-adjusted groups (B). SCC, squamous cell carcinoma; IPTW, inverse probability of treatment weighting.
Figure 3
Figure 3
Overall survival curves for stage I SCC of the anus for the unadjusted groups (A) and IPTW-adjusted groups (B). Overall survival curves for stage II SCC of the anus for the unadjusted groups (C) and IPTW-adjusted groups (D). SCC, squamous cell carcinoma; IPTW, inverse probability of treatment weighting.
See this image and copyright information in PMC

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