The efficacy of neoadjuvant chemoradiotherapy in signet ring cell carcinoma of the rectum: a retrospective propensity-score matched study

Abstract

INTRODUCTION: there is a lack of information chemoradiotherapy (CRT) efficacy in signet ring cell carcinoma of the rectum (SRCCR). The aim of our research was to investigate the efficacy of preoperative CRT in patients with SRCCR.PATIENTS AND METHODS: we conducted a retrospective analysis of medical records from the archive of Research Institute FSBI “N.N. Blokhin Cancer Research Center” of the Ministry of Health of Russia and multicenter registry of the Russian Society of Specialists in Colorectal Cancer (RSSCC) from 2000 to 2020 and included in the study group patients with histologically confirmed primary SRCCR who received preoperative CRT. A control group with rectal adenocarcinoma was created using propensity-score matching from the institutional database 1:1 taking into account sex, age, tumor size, the cT and cN clinical stage. We estimated the rate of Dworak tumor regression grade 3-4, RECIST, 5-year overall survival (OS) and disease-free survival (DFS) rates.RESULTS: the study and control group included 22 patients each. The study group included 11 patients (50%) with cT3 and cT4 clinical stage. 10 (45,5%) patients had cT3 clinical stage and 12 (54,5%) patients had cT4 clinical stage in the control group (p = 0,763). The number of patients with cN1-2 clinical stage was 17 (77,3%) and 16 (72,7%) in the study and control group, respectively (p = 0,728). The rate of Dworak tumor regression grade 3–4 was 40,9% in the group of patients with SRCCR and 45,5% in the group of patients with rectal adenocarcinoma (p = 0,761).When assessed by RECIST scale, 9 (40,9%), 12 (54,5%) and 1 (4,5%) patients with SRCCR had partial tumor response, stabilization and progression, respectively. Partial response was observed in 18 (81,8%) patients and stabilization — in 4 (18,2%) patients with rectal adenocarcinoma (p = 0,018). Median followup was 58,8 months. The 5-year OS was 34% in the SRCCR group and 71,3% in the group with rectal adenocarcinoma (p = 0,024), and the 5-year PFS was 30,2% with SRCCR and 52,2% with adenocarcinoma (p = 0,115).CONCLUSIONS: CRT leads to comparable grade 3–4 tumor regression in SRCCR and rectal adenocarcinoma, but the objective response rate is lower. This histological subtype has significantly lower OS values.