Impact of Radiation on Dysphagia-Related Structures: A Dosimetric and Clinical Comparative Analysis of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiation Therapy (IMRT) Techniques in Patients With Head and Neck Cancer.

Introduction Head and neck squamous cell carcinoma (HNSCC) is a significant health concern in India, with around one million new cases annually. The prevalence of HNSCC is notably high in Asia, especially in India, due to habits like tobacco chewing, betel nut usage, and alcohol consumption. Treatment typically involves a combination of surgery, radiation, chemotherapy, and biological therapy, aiming for tumor control while preserving function and quality of life. However, survivors often face long-term side effects like difficulty swallowing, leading to complications such as aspiration pneumonia. Intensity-modulated radiotherapy (IMRT) has shown promise in improving outcomes by sparing critical swallowing structures. Efforts to minimize radiation-related dysphagia are crucial for enhancing patients' quality of life post-treatment. Our study focuses on examining dosimetric parameters associated with dysphagia aspiration, alongside evaluating dysphagia grades in both treatment groups using the RTOG scale. Material and methods Patients with histologically confirmed non-metastatic head and neck carcinomas were included in our study in November 2018-April 2020. A total of 56 patients were taken into our study with 28 in each arm. They underwent radical radiotherapy (RT) with a total dose of 66-70 Gy, with or without concurrent chemotherapy, meeting specific inclusion criteria and excluding those receiving reirradiation or with distant metastasis. Patients were divided into two groups: Group I received three-dimensional conformal radiotherapy (3D-CRT), and Group II received IMRT. Treatment planning involved immobilization, CT imaging, delineation of target volumes and organs at risk, and contouring of swallowing structures. Dose-volume histogram parameters (mean dose, maximum dose, V30, V70, V80, D50, and D80) were used to assess mean dose to swallowing structures outside the planning target volume (PTV), with a mean dose constraint of 50 Gy. Dysphagia was evaluated using the RTOG criteria at baseline, during treatment, and six months post-treatment. Statistical analysis was performed using SPSS, with significance set at p < 0.05. Results In our study, the mean age at presentation differed slightly between the IMRT and 3D-CRT arms: 58 years versus 55 years, respectively. A higher proportion of patients in both arms experienced symptoms for three to six months, with 53.6% in 3D-CRT and 42.9% in IMRT. Stage distribution varied, with IV being most common in 3D-CRT and stage II in IMRT. Approximately 56% of patients in both groups had a history of smoking. Significant differences were observed in spinal cord dose between 3DCRT and IMRT techniques (p < 0.001). Similarly, a significant difference was found in the mean dose received by dysphagia aspiration-related structures (DARSs) between the 3D-CRT and IMRT arms (p = 0.04). Patients in the IMRT arm exhibited superior dysphagia grades compared to those in the 3D-CRT arm, with statistical significance observed in the third month (p = 0.008) and sixth month (p = 0.048). Conclusion Our study found a notable decrease in the mean DARS dose and reduced dysphagia severity at three and six months in the IMRT group compared to the 3D-CRT group. However, due to the diverse study population, establishing a definitive correlation between the DARS dose and dysphagia severity was challenging. Future large-scale studies are needed to validate these findings for improved preservation of DARS structures.