2082 - Real-World Data: Postoperative Concurrent Chemorradiation for Resected Locally Advanced Gastric Cancer - Treatment Patterns and Risk Stratification

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 27

POSTER

Presenter(s)

Salvador Gutierrez Torres, MD - Instituto Nacional de Cancerologia, Mexico City, CIUDAD DE MÉXICO

S. Gutierrez Torres Sr¹, G. Chavez-Tahuilan¹, J. Hinojosa Gomez¹, F. Maldonado - Magos¹, and B. A. Martínez-Cannon²; ¹Instituto Nacional de Cancerología, Mexico City, DF, Mexico, ²Instituto Nacional de Ciencias Médicas y Nutricion, Salvador Zubirán, Mexico City, DF, Mexico

Purpose/Objective(s):

Evidence supporting routine adjuvant chemoradiation (CRT) after D2 lymphadenectomy is inconsistent, and real-world data from underrepresented populations are limited. We described postoperative concurrent CRT patterns and identified prognostic factors in resected locally advanced gastric cancer.

Materials/Methods:

Retrospective, single-center cohort of consecutive adults (=18 years) with histologically confirmed, resected locally advanced gastric cancer treated with postoperative concurrent CRT (2016–2020). Treatment details were abstracted from the electronic record and radiotherapy (RT) planning system. Overall survival (OS) was defined from diagnosis to death or last follow-up; disease-free survival (DFS) from end of treatment to recurrence or progression. Survival was estimated with Kaplan–Meier and compared with log-rank tests. Cox proportional hazards models were used for univariable and multivariable analyses.

Results:

Sixty-six patients met eligibility criteria. Age =56 years: 51.5%; female: 51.5%; diffuse histology: 60.6%; ECOG 1–2: 78.8%. Pathology: pT4a 72.7%, N3 43.9%, grade 3 86.4%. Median examined nodes was 61 (range 20–249), median positive nodes 6 (0–47), and median lymph node ratio (LNR) 0.10 (0–0.88). R1 margins occurred in 9.1%. Concurrent chemotherapy was most commonly cisplatin/5-FU (74.2%). RT was delivered mainly with IMRT/VMAT (72.7%) to 45–54 Gy in conventional fractionation (45 Gy in 92.4%). On multivariable OS analysis, age =57 years (HR 1.906, 95% CI 1.017–3.572; p=0.044), pT4a (HR 3.679, 95% CI 1.519–8.907; p=0.004), and LNR =0.11 (HR 2.528, 95% CI 1.339–4.775; p=0.004) were associated with worse OS. For DFS, pT4a (HR 2.897, 95% CI 1.213–6.916; p=0.017) and LNR =0.11 (HR 3.782, 95% CI 1.885–7.588; p<0.001) were independently adverse. A simple risk score (pT4a and LNR =0.11; 0–2 points) stratified outcomes: 0 points (n=12), 1 point (n=29), 2 points (n=25); median OS was 3.55 years for 1 point versus 1.52 years for 2 points (log-rank p<0.001); median DFS for 2 points was <1 year (log-rank p<0.001).

Conclusion:

In patients receiving postoperative concurrent CRT, pT4a and LNR independently predicted OS and DFS. LNR is a practical risk-stratification metric that may help identify patients at highest risk after gastrectomy and adjuvant CRT, supporting tailored postoperative strategies and prospective validation.