Radiation induced brachial plexopathy in head and neck cancer patients treated with definitive radiotherapy and correlation with disease characteristics and dosimetric parameters.

Background: Definitive concurrent chemoradiotherapy (CRT) is the standard of care in advanced stages of head and neck cancer (HNC). With evident increase in survival rate there is also simultaneous increase in toxicity affecting the quality of life. One of the less researched late toxicity is radiation induced brachial plexopathy (RIBP). In this dosimetric study we intent to contour the brachial plexus (BP) as an organ at risk (OAR) and determine the factors that contribute to dose variations to BP, and clinically evaluate the patients for RIBP during follow-up using a questionnaire. Materials and methods: 30 patients with HNC planned for CRT from September 2020 to June 2022 were accrued. Patients were treated to a dose of 6600 cGy with intensity modulated radiotherapy using the simultaneous integrated boost technique. From the dose-volume histogram (DVH) statistics the BP volume, Dmax and other parameters like V66, V60 were assessed and was correlated with respect to primary tumour and nodal stage. Results: On corelation, more than the T stage, the N stage and the primary location had a significant impact on the Dmax. With a median follow-up of 17.9 months, the incidence of RIBP was 6.67%. The 2-year disease free survival and the 2-year overall survival were 53.7% and 59.4%, respectively. Conclusions: In oropharyngeal/hypopharyngeal primaries and in advanced nodal disease, BP receives higher doses contributing to RIBP. Primary tumor and nodal stage also impacted V60 and V66 of BP. Hence, contouring of BP as an OAR becomes imperative, and respecting the DVH parameters is essential.