2262 - Locally Recurrent Rectal Cancer: Is Omission of Elective Nodal Irradiation Feasible? — A Propensity Score-Matched Analysis in 186 Patients

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 19

POSTER

Presenter(s)

Feng-peng Wu, MD - Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei

F. P. Wu, Y. Ren, L. L. Xiao, J. Sun, and Y. Liu; Department of Radiation Oncology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, China

Purpose/Objective(s):

To compare the efficacy of elective nodal irradiation (ENI) versus involved-field irradiation (IFI) in patients with locally recurrent rectal cancer (LRRC) and to identify prognostic factors.

Materials/Methods:

A retrospective analysis was performed on 186 patients with pelvic locally recurrent rectal cancer treated at our institution between February 2012 and September 2025. The cohort included 114 patients who received IFI and 72 who received ENI. After propensity score matching (PSM) to balance baseline characteristics, 46 patients remained in each group. Post-relapse overall survival (Pr-OS) and progression-free survival after recurrence (PFS2) were compared using the Kaplan-Meier method and log-rank test. Prognostic factors were analyzed using Cox proportional hazards models.

Results:

After PSM, baseline characteristics were well-balanced. The extent of the radiotherapy field (ENI vs. IFI) did not significantly impact survival outcomes. The 1-, 3-, and 5-year Pr-OS rates were 93.2%, 30.3%, and 6.9% for the ENI group, and 93.4%, 35.8%, and 6.1% for the IFI group (HR: 0.979, 95% CI 0.618-1.553, P=0.929), respectively. The corresponding PFS2 rates were 75.6%, 17.7%, 3.0% (ENI) and 75.9%, 25.9%, 2.7% (IFI)(HR: 0.936, 95% CI 0.608-1.443, P=0.765). Multivariate analysis identified the distant metastasis as the only independent factor affecting Pr-OS (HR: 0.542, 95% CI 0.313-0.938, P=0.029). The occurrence of grade =3 treatment-related adverse events was the only independent factor influencing PFS2 (HR: 0.607, 95% CI 0.380-0.970, P=0.037).

Conclusion:

Compared with ENI, IFI did not negatively impact survival outcomes in patients with LRRC. The necessity of prophylactic irradiation using an extended pelvic field warrants further investigation.