Conformal radiation therapy versus volumetric arc therapy in high dose concurrent chemoradiotherapy for carcinoma esophagus: A retrospective analysis

Abstract

Background: Esophageal epithelium being primarily squamous, numerous studies have attempted to deliver a dose of more than 60 Gy as a part of radical chemoradiation for locally advanced esophageal cancer to achieve better tumor control. Various techniques have been explored in an attempt to spare the lung and heart from receiving high doses of radiation while delivering radiation to the primary tumor. Objectives: We aimed to compare the doses received by different organs at risk (OARs) and toxicities. We also aimed to compare the overall survival (OS) and disease-free survival (DFS) between patients treated with conformal radiation therapy and Volumetric Modulated Arc Therapy (VMAT). Materials and Methods: This was a retrospective audit of standard treatment offered to patients with esophageal cancer registered at our hospital between June 2015 and August 2019 using different radiotherapy techniques. Patients were treated using conformal radiation therapy or VMAT. The radiation dose delivered varied from 50.4 Gy in 28 fractions to 63 Gy in 35 fractions, depending on the OARs according to the tumor location and histology. Patients were followed up until December 2020. The Kaplan–Meier method was used for survival analysis. The log-rank test was used to compare the OS and DFS rates in the univariate analysis, and the Cox proportional-hazards model was used for the multivariate analysis. Results: Of a total of 115 patients included in the study, 16 received radiation therapy using conventional telecobalt, 25 received three-dimensional conformal radiation therapy (3DCRT), 10 received 3DCRT plus intensity-modulated radiation therapy (IMRT) Phase-II, and 64 received VMAT. For the purpose of this analysis, the three modalities other than VMAT were categorized as conformal radiation therapy. The median follow-up period was 9 months (range, 0–55) in both groups. The mean doses and sub-volume doses received by the heart were significantly lower in VMAT compared to conformal radiotherapy (mean doses 20 Gy vs. 35 Gy, P = 0.001). There was no significant difference in acute (P = 0.39) or late (P = 0.36) pharyngoesophagitis between the two groups. The OS and DFS were not significantly different between the two groups; median OS was 13 months in the VMAT and 17 months in the conformal radiotherapy group, P = 0.8; the median DFS was 8 months versus 7 months, respectively, P = 0.16. None of the tumor-related factors, except concurrent chemotherapy, significantly affected the OS and DFS in the univariate and multivariate analyses. Conclusion: The radiation dose received by the heart is significantly lower when using VMAT compared to conformal radiation therapy. However, there is no significant difference in the survival outcomes between the two techniques. The addition of concurrent chemotherapy significantly prolongs survival.