A Study Evaluating the Contribution of Non-Coplanar Beam Arrangement in Reducing Toxicity in Radiotherapy for Upper Aerodigestive Tract Cancers

Cancers of the upper aerodigestive tract (UADT) are frequently treated with external beam radiotherapy, either alone or in combination with chemotherapy. Despite major advances achieved with intensity-modulated radiotherapy (IMRT/VMAT), irradiation of organs at risk (OARs) remains unavoidable and may lead to acute and late toxicities such as xerostomia, hyposalivation, swallowing disorders, and impaired quality of life. These toxicities are closely related to the dose delivered to salivary glands and other critical structures, and recommended OAR dose constraints are often exceeded to ensure adequate tumor coverage.

Non-coplanar beam arrangements (NCBA) represent a potential strategy to further reduce radiation dose to OARs while maintaining equivalent target coverage. However, their clinical implementation has been limited due to technical complexity and the risk of collisions between the linear accelerator and the patient. The recent implementation of the opto-numerical solution MapRT® (VisionRT), based on three-dimensional modeling of the patient and the linear accelerator, allows safe and reliable identification of feasible non-coplanar beam trajectories. Retrospective dosimetric analyses conducted at our institution have demonstrated significant dose reductions to several OARs in UADT cancer patients treated with NCBA compared with conventional coplanar beam arrangements, without compromising tumor dose coverage.

BaReTox is a prospective, open-label, randomized, single-center pilot trial designed to evaluate the clinical impact of non-coplanar beam radiotherapy on treatment-related toxicities and quality of life in patients with non-operated, non-metastatic squamous cell carcinoma of the oral cavity or oropharynx. Adult patients eligible for curative-intent bilateral radiotherapy, with known HPV (p16) status, are randomized to receive either standard coplanar radiotherapy (control arm) or non-coplanar radiotherapy (experimental arm), with or without concomitant chemotherapy. All patients receive a standard photobiomodulation protocol during radiotherapy.

The primary objective is to compare the change in head and neck cancer-specific quality of life between baseline and three months after completion of radiotherapy, assessed using the EORTC QLQ-H&N35 questionnaire, focusing on swallowing, social eating, and dry mouth domains. Secondary objectives include comparison of acute and late toxicities graded according to CTCAE version 5.0, assessment of salivary function by sialometry, evaluation of global and disease-specific quality of life over time, progression-free survival, feasibility of delivering non-coplanar radiotherapy, dosimetric impact on organs at risk, and evaluation of radiation-induced lymphopenia.

This pilot study aims to provide clinical proof of concept for the benefit of non-coplanar beam radiotherapy in reducing toxicity and improving quality of life in patients with UADT cancers