Reduced acute and late toxicities with intensity-modulated radiation therapy compared to three-dimensional conformal radiation therapy in post-operative gastric cancer

Abstract

The role of intensity-modulated radiation therapy (IMRT) in post-operative gastric cancer is unknown. We evaluated the toxicity profiles of post-operative gastric cancer patients treated with IMRT or three-dimensional conformal radiation therapy (3D-CRT). We identified patients with gastric cancer treated with post-operative radiation at our institution between 2002 and 2016. Acute and late toxicities were evaluated per RTOG/EORTC Radiation Toxicity Grading Scale. Statistical analysis was performed using Chi-square tests, t tests, log-rank, and logistic regression. We identified 66 patients who underwent surgical resection as part of planned definitive treatment. Eighty percent of patients had T3 or higher disease, while 67% had N2+ disease. Thirty patients received 3D-CRT, while 36 received IMRT. Patients receiving 3D-CRT were younger in age than IMRT, treated longer ago, and did not receive neoadjuvant chemotherapy. Acute grade 2 lower GI toxicity was higher with 3D-CRT (40% vs 17%, p = 0.04). 3D-CRT had higher rates of late lung toxicity of any grade (23% vs 3%, p = 0.02), grade 3+ late esophageal toxicity (23% vs 3%, p = 0.02), and grade 2+ late intestinal toxicity (19% vs 0% p = 0.01). Dosimetric analysis showed that keeping Bowel V5 ≤ 93% protected against development of acute lower GI toxicity of any grade, with V5 ≤ 93% resulting in 10.5% incidence, and V5 > 93% resulting in 52% incidence (p = 0.004). Use of IMRT in post-operative gastric cancer is associated with reduced acute and late toxicities. Consideration should be given for prospective evaluation in the future.