Gross tumor volume dosimetry and prognosis of esophageal carcinoma treated with three-dimensional radiotherapy: a study of 548 patients

Abstract

Objective To investigate the effects of dosimetric differences in gross tumor volume (GTV) on local control and survival rates in patients with esophageal carcinoma undergoing three-dimensional (3D) radiotherapy, and to provide a basis for clinical treatment. Methods From January 2004 to December 2010, 548 patients with esophageal carcinoma received conventional fractionated 3D radiotherapy with a prescribed dose of 60 Gy. All patients were divided into low-dose group and high-dose group according to the dosimetric differences in GTV.The survival and local control rates were compared between the two groups. The survival rates were calculated using the Kaplan-Meier method and analyzed using the logrank test. The Cox regression model was used for the multivariate prognostic analysis. Results The number of sample were 456 and 216 patients at 5 and 7 years followed time. The 1-, 3-, 5-, and 7-year local control rates were significantly higher in the high-dose group than in the low-dose group (83.5% vs. 71.3%, 62.6% vs. 44.8%, 57.5% vs. 41.7%, 52.9% vs. 38.8%, P=0.000). The 1-, 3-, 5-, and 7-year survival rates were also significantly higher in the high-dose group than in the low-dose group (79.6% vs. 66.3%, 44.3% vs. 29.7%, 34.0% vs. 21.8%, 26.1% vs. 17.0%, P=0.000). The univariate prognostic analysis using the Cox regression model showed that Dmin, Dmean, and D100 for GTV were prognostic factors (P=0.000, 0.001, 0.000). In all the 548 patients, 201 were assigned to the high-dose group and the others to the low-dose group. Compared with the high-dose group, the low-dose group showed significantly larger GTV (38.2 vs. 48.1 cm3, P=0.002) and more advanced T stages (P=0.035). The stratified analysis showed that the 1-, 3-, 5-, and 7-year local control and survival rates were significantly higher in the high-dose group than in the low-dose group, regardless of tumor location, GTV, TNM stage, or chemotherapy. The multivariate analysis using the Cox regression model indicated that tumor location and grouping based on the radiation dose to GTV were independent prognostic factors. Conclusions In 3D radiotherapy for treating esophageal carcinoma, a high-quality treatment plan and GTV dose assurance improve the survival rates in patients. The patients with lower Dmin, Dmean, and D100 for GTV than the prescribed dose have a poor prognosis. Key words: Esophageal neoplasms/three-dimensional radiotherapy; Gross tumor volume; Prognosis