Dosimetric Comparison of Three-Dimensional Conformal Radiotherapy and Intensity-Modulated Radiotherapy for Gastric and Gastroesophageal Junction Cancers: A Paired Planning Study

Abstract

Background: Radiotherapy for gastric and gastroesophageal junction (GEJ) cancers is technically challenging because of complex upper abdominal anatomy and the proximity of critical organs at risk (OARs). This study aimed to perform a paired dosimetric comparison between three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in patients with gastric and GEJ cancers. Methods: This retrospective dosimetric planning study included 45 patients with histologically confirmed, non-metastatic gastric or GEJ adenocarcinoma. For each patient, two independent radiotherapy plans were generated on the same computed tomography (CT) dataset: a conventional fourfield 3D-CRT plan and a seven-field coplanar IMRT plan. Both techniques prescribed a total dose of 45 Gy delivered in 25 fractions. Dose–volume histogram (DVH) analysis was used to evaluate planning target volume (PTV) coverage and doses to OARs, including the liver, kidneys, and spinal cord. Results: Both techniques achieved adequate PTV coverage. IMRT demonstrated significantly superior dose conformity compared with 3D-CRT (conformity index: 1.29 vs. 1.58; p < 0.001). In contrast, 3D-CRT showed slightly better dose homogeneity (homogeneity index: 1.08 vs. 1.09; p = 0.029). IMRT resulted in a significantly lower mean liver dose (21.66 Gy vs. 26.23 Gy; p < 0.001). Renal dosimetric parameters showed technique-dependent variations without statistically significant differences. The maximum spinal cord dose was significantly lower with 3D-CRT (30.50 Gy vs. 33.60 Gy; p = 0.036). Conclusion: Both 3D-CRT and IMRT provide acceptable target coverage for gastric and GEJ cancers, with complementary advantages. IMRT offers superior conformity and improved liver sparing, whereas 3D-CRT provides better dose homogeneity and lower spinal cord dose. Radiotherapy technique selection should therefore be individualized based on tumor location, patient anatomy, and OAR priorities.