ESTRO 2024 - Abstract Book

S1256

Clinical - Head & neck

ESTRO 2024

1132

Digital Poster

Adjuvant Intensity Modulated Radiation Therapy in Oral Cavity Carcinomas with Pedicled Flap

Pritha Roy, Shwetabh Sinha, Rabi Das, Anuj Kumar, Samarpita Mohanty, Ashwini Budrukkar, Monali Swain, Faizalam Khan, Sarbani Ghosh Laskar

Tata Memorial Centre, Radiation Oncology, Mumbai, India

Purpose/Objective:

Target delineation for adjuvant Intensity-Modulated Radiation Therapy (IMRT) for Oral Cavity Squamous Cell Carcinomas (OCSCC) with pedicled flaps remains controversial due to distortion of the normal anatomy in the post operative neck. The extent of inclusion of the contralateral neck nodes in the elective nodal target volumes in well lateralized, non-oral tongue and floor of mouth OCSCC is another contentious issue.

Material/Methods:

This retrospective observational study included patients with OCSCC who had undergone primary surgery followed by reconstruction with a pedicled regional flap (PMMC, PMMF, bi-paddle PMMC, deltopectoral flap, Lattisimus dorsi flap, Supraclavicular flap) and adjuvant IMRT (+/- chemotherapy) between January 2010 to June 2020. The pre operative imaging was fused with the post-operative planning CT scan wherever available. The pre-operative primary tumor was delineated and projected onto the planning CT scan. During target volume delineation, the pre surgical gross tumor volume with an additional isotropic margin of 5-10mm (edited from natural anatomical boundaries) constituted the primary tumor bed. Additionally, the flap and body tissue junction were given a margin of 5-10 mm (if not already given). An effort was not made to trace the flap for inclusion in the clinical target volume (CTV), except when it traversed through the involved nodal regions. The high risk CTV included the primary tumor bed and involved lymph nodal regions. The rest of the ipsilateral lymph nodes were included in the low risk CTV. Contralateral nodes (Ib/II +/- III) were treated electively in all tongue cancers, all tumors crossing midline, and in buccoalveolar complex patients with heavy nodal burden at level Ib (more than two nodes with Extracapsular extension at Ib). The primary outcomes measured were locoregional control, disease-free survival, overall survival, patterns of failure, and toxicities.

Results:

One hundred and seventy patients were screened, and 143 patients were included in the analysis. The median age of the cohort was 49 years (IQR:41-57), with a majority of 135 (94.5%) patients being male and 127 (88.8%) being tobacco users. The most common sub-site of disease was buccal mucosa in 78 (54.5%) patients, followed by 36 (25.2%) oral tongue cancers. A majority of 104 (72.7%) patients had pathological T3-T4 disease, whereas 78 (54.5%) patients had pathological N0-N1 disease followed by 64 (44.8%) patients with N2-N3 nodes positive. Twenty-three (16.1%) patients had received induction chemotherapy before surgery. All but one patient underwent ipsilateral neck dissection, and 34 (23.8%) patients had contralateral neck dissection. Extra Nodal Extension (ENE) was seen in 51 (35.7%) patients and 11 (7.7%) patients had close or positive margins. The median RT dose was 60Gy (IQR: 60-60).