Comparison of oncological outcomes of T1-3 N1 rectal cancer patients treated with neoadjuvant radiotherapy versus no radiotherapy: A retrospective cohort study.

Abstract

Background and aims: Neoadjuvant short-course radiotherapy (SCRT) prior to surgery has been used to reduce local recurrences in moderately advanced rectal cancer (RC). Total mesorectal excision (TME) surgery by itself can reduce the local recurrence rate in these patients. The objective was to assess whether discontinuing neoadjuvant SCRT had a negative impact on survival and local recurrence rates of moderately advanced RC.

Methods: This retrospective study examined 137 consecutive patients (67 neoadjuvant SCRT, 70 TME without neoadjuvant therapy) treated for rT1-3N1M0 RC without extramural venous invasion (EMVI) or a threatened surgical margin between January 2016 and March 2020 in a tertiary rectal surgery referral center. The primary objective was the impact of neoadjuvant therapy on overall, cancer-specific, and disease-free survival, and local recurrence rate. Secondary outcomes were risk factors affecting survival. The analyses were conducted on the total study cohort as well as a propensity score matched cohort of the same patient group, with the matching predicated upon age, gender, and histological T score.

Results: The oncological outcomes were similar between the two different treatment groups. The 5-year cumulative overall survival rate, calculated using the Kaplan-Meier method, was 89.6% in the neoadjuvant SCRT group and 83.5% in the surgery-only group (p = 0.570), with the corresponding cancer-specific survival rates at 97.0% and 98.4% (p = 0.219) and disease-free survival rates at 97.0% and 91.9% (p = 0.438). No local recurrencies were detected in either group during the 5-year follow-up period.

Conclusion: The omission of neoadjuvant SCRT in rT1-3N1M0 RC with no EMVI and no threatened resection margin caused no adverse effects on the survival of the patients. Based on this series, it appears that avoiding SCRT does not compromise the oncological outcome in these patients.