ESTRO 2024 - Abstract Book

S1498

Clinical - Lower GI

ESTRO 2024

Keywords: Organ preservation, rectal cancer, dose escalation

912

Digital Poster

Efficacy of adjuvant radiotherapy after local excision of early-stage rectal cancer

Soo Jin Lee 1 , Changhoon Song 2 , Seung Hyuck Jeon 2 , Eui Kyu Chie 1 , Kyung Su Kim 1 , Seung-Yong Jeong 3 , Sung-Bum Kang 4 , Jae-Sung Kim 2 1 Seoul National University College of Medicine, Department of Radiation Oncology, Seoul, Korea, Republic of. 2 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam, Korea, Republic of. 3 Seoul National University College of Medicine, Department of Surgery, Seoul, Korea, Republic of. 4 Seoul National University Bundang Hospital, Department of Surgery, Seongnam, Korea, Republic of

Purpose/Objective:

After local excision of early-stage rectal cancer, patients with risk factors are strongly recommended to undergo completion total mesorectal excision (TME), while adjuvant radiotherapy (ART) may be considered in patients who are medically inoperable or desire to avoid TME-related morbidities. However, the efficacy of ART compared to completion TME after local excision remains controversial. This study aimed to evaluate the efficacy of ART compared with TME.

Material/Methods:

This retrospective analysis included 244 patients diagnosed with pT1-2 rectal cancer on local excision (194 underwent TME, 50 received ART), eligible for either TME or ART, treated at two tertiary referral hospitals from January 1, 2000, to December 31, 2022. The primary endpoint was locoregional recurrence rate. Secondary endpoints included distant metastasis rate, overall survival, and permanent stoma free rate. Outcomes between treatments were analyzed through propensity score matching (PSM) using logistic regression with a 2:1 match ratio and replacement. Subgroup analysis was done in lower rectal cancer patients.

Results:

In the PSM analysis, the 2:1 matched cohort comprised 90 patients (60 TME, 30 ART). Among ART patients, 13 (26%) received capecitabine, 10 (20%) 5-fluouracil, and 7 (14%) oral uracil- tegafur plus leucovorin. After PSM, there was no statistical difference in clinicopathologic factors such as age, sex, tumor location, pT2 stage, grade 3, lymphovascular invasion and positive resection margins between TME and ART groups. Median follow-up was 6.3 years (IQR 3.6 - 9.4) versus 5.3 years (IQR 3.4 - 7.4), respectively. Locoregional recurrence was observed in 0 (0%) of TME patients and 1 (3%) of ART patients. Distant metastasis was manifested in 6 (10%), 1(3%) with TME and ART respectively. Outcomes for TME and ART were not statistically different for locoregional recurrence, distant metastasis, and overall survival (all P > 0.05). After subgroup analysis in lower rectal cancer patients, there were no differences in treatment outcomes (all P > 0.05) while permanent stoma was in 3 (5%), 0 (0%) with TME and ART, respectively.