ESTRO 2024 - Abstract Book

S1474

Clinical - Lower GI

ESTRO 2024

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Mini-Oral

Significance of persistent lymph node metastase after neoadjuvant chemoradiotherapy in rectal cancer

Markus Diefenhardt 1,2 , Daniel Martin 1,3 , Ralf-Dieter Hofheinz 4 , Michael Ghadimi 5 , Emmanouil Fokas 1,2,3 , Claus Rödel 1,2,3 , Maximilian Fleischmann 1 1 Goethe University Frankfurt, University Hospital, Department of Radiotherapy and Oncology, Frankfurt, Germany. 2 2Goethe University Frankfurt, Frankfurt Cancer Institute (FCI), Frankfurt, Germany. 3 3German Cancer Research Center (DKFZ) and German Cancer Consortium (DKTK), partner site Frankfurt, Frankfurt, Germany. 4 University Heidelberg, University Hospital Mannheim, Department of Medical Oncology, Mannheim, Germany. 5 University Göttingen, University Medical Center Götti, Department of General, Visceral and Pediatric Surgery, Göttingen, Germany

Purpose/Objective:

To analyze the association of persistent lymph node metastases with pretreatment clinicopathologic parameters and intensity of neoadjuvant treatment on long-term oncologic outcomes in patients with rectal cancer treated within three consecutive randomized trials of the German Rectal Cancer Study Group (GRCSG).

Material/Methods:

This is a secondary analysis of 1948 patients with locally advanced rectal cancer, recruited between February 1995 and January 2018, in three randomized clinical trials of the GRCSG (CAO/ARO/AIO-94, CAO/ARO/AIO-04, and CAO/ARO/AIO-12). Comparisons between pretreatment clinicopathologic characteristics and intensity of preoperative treatment with pathologic lymph node status (ypN0/1/2) were analyzed using Pearson's chi-squared test or Kruskal-Wallis test. The cumulative incidence of locoregional recurrence and distant metastasis, with death as competing risk, and overall survival (OS) were analyzed with the Gray's test and the log-rank test, respectively. Analyses were performed using R statistical software version 4.2.2.

Results:

A total of 1888 of 1948 randomized patients were eligible for this analysis; 1009 had received standard preoperative 5-FU-based chemoradiotherapy (CRT, comprising the preoperative group of CAO/ARO/AIO-94, and the control group of -04), 586 had received 5-FU-CRT combined with oxaliplatin (5-FU/OX-CRT, experimental group of -04), and 293 had received total neoadjuvant treatment with 5-FU/OX-CRT plus 3 cycles of induction or consolidation FOLFOX chemotherapy within the -12 trial. Persistent positive pathologic lymph nodes after neoadjuvant treatment were detected in 552 patients (29%); 378 had ypN1 (20%), and 174 had ypN2 (9%). Patients