2280 - A Prospective Pathological Study to Refine Radiotherapy CTV Delineation for ESCC After Neoadjuvant Chemoimmunotherapy

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 26

POSTER

Presenter(s)

Hang Yin, MD, PhD - Harbin Medical University Cancer Hospital, Harbin, Heilongjia

H. Yin, G. Liang, J. Yang, Y. Wang, Y. Zhou, J. Ma, and X. Wang; Harbin Medical University Cancer Hospital, Harbin, China

Purpose/Objective(s):

The optimal clinical target volume (CTV) for radiotherapy remains undefined in esophageal squamous cell carcinoma (ESCC) patients following combined chemotherapy and immunotherapy (CCI). This study aimed to use large-scale pathological analysis of surgical specimens to evaluate microscopic extension (ME) and guide precise CTV delineation.

Materials/Methods:

In this prospective analysis, we examined surgical specimens from 80 ESCC patients (32 direct surgery (DS); 48 neoadjuvant chemoimmunotherapy(NACI), including 30 responders and 18 non-responders). CTV boundaries were determined by measuring ME along the esophageal wall.

Results:

Histopathological evaluation showed significant ME differences: DS group (3.54 mm ± 8.00 mm), NACI responders (0.32 mm ± 0.88 mm), and NACI non-responders (3.00 mm ± 5.23 mm). Based on the 95th percentile of ME distribution, we propose differential craniocaudal CTV margins beyond the gross tumor volume (GTV): 26 mm for DS, 2 mm for NACI responders, and 15 mm for NACI non-responders.

Conclusion:

Histopathological analysis revealed differential ME patterns in ESCC patients after CCI, stratified by treatment response. For locally advanced ESCC receiving CCI, we propose individualized CTV delineation: 2 mm craniocaudal margins for responders versus 15 mm for non-responders. This response-adapted protocol provides 95% ME coverage while optimizing organ-at-risk sparing.