Retrospective Analysis of Dosimetric Comparison Between Intensity-Modulated Radiation Therapy and Volumetric-Modulated Arc Therapy in Patients With Esophageal Cancer.

Introduction Esophageal cancer is a significant global health concern, with high incidence and mortality rates, particularly in India, where it ranks among the top causes of cancer-related deaths. Radiotherapy plays a critical role in the treatment of advanced-stage esophageal cancer. This study aims to compare the dosimetric outcomes of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) to evaluate their efficacy and safety in managing mid-esophageal carcinoma.  Materials and methods A retrospective study was carried out on thirty patients with middle-third esophageal cancer who received treatment at Rohilkhand Medical College and Hospital, Bareilly, India. The patients, aged between 50 and 70 years (mean age of 66.5 years), were in stages II to III of cancer according to the American Joint Committee on Cancer (AJCC) 2018 guidelines. All patients had histologically confirmed cases of moderately differentiated squamous cell carcinoma. The treatment procedure included immobilization using a thoracic mold, CT simulation with intravenous and oral contrast, and contouring of the gross tumor volume (GTV), clinical target volume (CTV), planning target volume (PTV), and organs at risk (OARs) following the Radiation Therapy Oncology Group (RTOG) 0436 protocol. VMAT planning was done using the Varian Eclipse™ Treatment Planning System, while IMRT planning employed a seven-field non-coplanar beam setup. Comparative virtual IMRT plans were generated for these patients. Both VMAT and IMRT plans were evaluated based on dosimetric parameters for the PTV and OARs. Results Both VMAT and IMRT achieved sufficient PTV coverage, with no statistically significant differences in dosimetric parameters (dose to 99 % volume of PTV, dose to 95 %volume of PTV, maximum dose to PTV, minimum dose to PTV). VMAT demonstrated reduced lung and heart doses compared to IMRT; however, the observed differences were not statistically significant. There was a reduction in lung dose with VMAT when evaluating the dose-volume constraints: volume receiving 15 Gy dose (V15) by 11%, volume receiving 20 Gy dose (V20) by 20%, and volume receiving 25 Gy dose (V25) by 41%, though these differences were not statistically significant. The mean maximum spinal cord dose was significantly lower with VMAT (19.69 Gy) compared to IMRT (30.80 Gy, p=0.01). Heart dosimetry showed slight improvements with VMAT, particularly in volume receiving 30 Gy dose (V30), volume receiving 40 Gy dose (V40), and mean heart dose, though these differences were not statistically significant. Conclusion Both VMAT and IMRT provided similar PTV coverage. VMAT showed a reduction in spinal cord dose, which was statistically significant, and a trend toward lower lung and heart doses, though these differences were not statistically significant. VMAT appears to be an effective option for treating mid-esophageal carcinoma while reducing exposure to critical organs.