Evaluation of Late Toxicities in Postoperative Cases of Oral Cavity Cancer Treated by Intensity-Modulated Radiotherapy (IMRT): A Retrospective Cohort Study

Introduction: Surgical intervention serves as the primary treatment modality for operable oral cavity cancer. However, patients with locally advanced disease or unfavourable prognostic factors often require adjuvant Radiotherapy (RT) with or without concurrent Chemotherapy (CT). Advanced radiation techniques, such as Intensity-Modulated Radiotherapy (IMRT), have shown potential in minimising radiation-related toxicities while ensuring effective tumour control.Aim: To assess common late toxicities, namely xerostomia, dysphagia, and hoarseness, in patients with postoperative Squamous Cell Carcinoma (SCC) of the oral cavity, who received adjuvant RT or concurrent Chemo-Radiotherapy (CRT) utilising IMRT with a Simultaneous Integrated Boost (SIB) approach.Materials and Methods: A retrospective cohort study was conducted in the Department of Radiotherapy at IMS, BHU, Varanasi, Uttar Pradesh, India, from June 2018 to December 2021. Study was done using the medical records of 62 patients with SCC of the oral cavity and received adjuvant radiation by the IMRT technique with or without concurrent CT. Late toxicities were evaluated according to the Common Terminology Criteria for Adverse Events version 3.0 (CTCAE v3.0). Statistical analysis was performed using Statistical Package for Social Sciences (SPSS) software version 28.0, and a logistic regression modelwas used to establish the association between Organ-At-Risk (OAR) doses and the development of late toxicities.Results: The median age of the study participants was 45 years (range: 25-68), and 95.2% (n=59) of the patients were male. A total of 62 patients (59 male, 3 female) were included. The median follow-up duration was 21.5 months. At two years, the cumulative incidence of xerostomia, dysphagia, and hoarseness was 28.5% (n=8), 21.4% (n=6), and 28.5% (n=8), respectively. Logistic regression showed that both the D mean of >26 Gy to the contralateral parotid (HR=4.32; 95% CI, 1.03-18.05; p=0.045) and the D mean of >26 Gy to the contralateral Submandibular Gland (SMG) (HR=6.41; 95% CI, 1.48-27.81; p=0.013) were significantly associated with the incidence of xerostomia. The D mean of >47 Gy to the pharyngeal constrictors (HR=17.89; 95% CI, 3.15-101.62; p=0.001) and the D mean of >50 Gy to the larynx (HR=5.77; 95% CI, 1.82-18.24; p=0.003) had a significantly high risk of dysphagia and hoarseness, respectively.Conclusion: Adjuvant IMRT resulted in acceptable rates of late toxicities in oral cancer. Doses to the contralateral parotid and SMGs, pharyngeal constrictors, and larynx had a significant impact on late xerostomia, dysphagia, and hoarseness, respectively.