1056 - Evaluating Changes in Tumor Volumes Following Expert Interpretation of Planning Imaging in Head and Neck Cancer Radiotherapy

03:10pm - 03:15pm ET

Room 107

Presenter(s)

Colin Belliveau, MD - Centre Hospitalier de l'Universite de Montreal (CHUM), Montreal, QC

C. Belliveau¹, P. F. Nguyen-Tan¹, E. Filion¹, K. Nelson², L. Létourneau-Guillon², S. Lam², P. Gilbert², D. Juneau³, C. H. Shih³, A. Christopoulos⁴, and H. Bahig¹; ¹Département de radio-oncologie, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, QC, Canada, ²Département de radiologie, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, QC, Canada, ³Département de médecine nucléaire, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, QC, Canada, ⁴Département d’oto-rhino-laryngologie, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, QC, Canada

Purpose/Objective(s):

Advanced imaging modalities, including magnetic resonance imaging (MRI) and computed tomography (CT), play a critical role in defining tumor extent and guiding clinical decision-making in head and neck (HN) radiotherapy planning. However, planning images are not routinely interpreted by experts. At our institution, multimodal imaging is systematically incorporated into treatment planning. However, delays may occur between diagnostic and planning imaging, and MRI is not consistently included in the initial diagnostic workup. In this study, we evaluated how often all planning images, systematically reviewed by a radiologist, led radiation oncologists to modify target volumes.

Materials/Methods:

In this prospective study at a high-volume, quaternary HN cancer center, radiation oncologists completed a survey to report treatment volume modifications after expert review of planning images by radiologists. Prior to radiotherapy initiation, planning images were systematically evaluated by expert HN radiologists. Once contours were finalized, the survey asked radiation oncologists whether primary or nodal volumes were modified and whether additional examinations were requested based on the expert interpretation.

Results:

From August 2023 to December 2025, 700 surveys were completed. For primary tumor volumes (n=700), modifications occurred in 176 patients (25%): 156/700 (22%) for T1 MRI, 10/700 (1.4%) for T2 MRI, and 31/700 (4.4%) for CT. For nodal volumes (n=577), changes occurred in 60 patients (10%): 28/577 (4.9%) for T1 MRI, 6/577 (1.0%) for T2 MRI, and 30/577 (5.2%) for CT. Complementary examinations or treatment plan changes were requested in 28% (123/435) of patients after expert interpretation, most commonly follow-up chest CT (n=55), neck or thyroid ultrasound (n=16), PET (n=11), brain imaging (n=9), medical consultations (n=7), abdominal imaging (n=6), surgery instead of primary radiotherapy (n=3), biopsy of new lesions (n=3), spine MRI (n=2), neoadjuvant chemotherapy (n=2), and antibiotic prescriptions (n=2).

Conclusion:

Expert imaging interpretation substantially alters target delineation for HN cancers, particularly for primary tumors, with contour modifications in 25% of cases. Nodal volume changes, though less frequent (10%), remain clinically meaningful. In the era of treatment de-intensification and adaptive radiotherapy planning, even modest contour modifications may be of increasing clinical importance.