Ann Surg Treat Res.  2022 Sep;103(3):176-182. 10.4174/astr.2022.103.3.176.

Association between microsatellite instability and tumor response to neoadjuvant chemoradiotherapy for rectal cancer

Affiliations
  • 1Department of Surgery, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun, Korea
  • 2Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Korea
  • 3Department of Pathology, Chonnam National University Hwasun Hospital, Chonnam National University Medical School, Hwasun, Korea

Abstract

Purpose
The relationship between microsatellite instability (MSI) and tumor response after neoadjuvant chemoradiotherapy (nCRT) in rectal cancer remains unclear. The present study aimed to evaluate the association between MSI and tumor response to nCRT in rectal cancer treatment.
Methods
Patients with rectal cancer from 2 tertiary hospitals who underwent nCRT, followed by radical surgery, were included. The microsatellite status was determined using a PCR-based Bethesda panel. Tumors with a Dworak’s tumor regression grade of 3 or 4 were considered to have a good response. Predictive factors for a good response to nCRT were analyzed.
Results
Of the 1,401 patients included, 910 (65.0%) had MSI results and 1.5% (14 of 910) showed MSI-H. Among all the patients, 519 (37.0%) showed a good response to nCRT. A univariate analysis showed that MSI-H tended to be negatively associated with a good response to nCRT, but no statistical significance was observed (7.1% vs. 24.1%, P = 0.208). Multivariate analysis showed that well-differentiated tumors were the only predictive factor for good response to nCRT (odds ratio [OR], 2.241; 95% confidence interval [CI], 1.492–3.364; P < 0.001). MSI status tended to be associated with the response to nCRT (OR, 0.215; 95% CI, 0.027–1.681; P = 0.143).
Conclusion
MSI-H was not associated with response to nCRT in patients with rectal cancer.

Keyword

Chemoradiotherapy; Microsatellite instability; Rectal neoplasms
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