Comparison of static intensity-modulated radiation therapy and volumetric modulated arc therapy in early-stage primary mediastinal B-cell lymphoma

Abstract

Objective To compare target dosimetric distribution and normal tissue radiation between different static intensity-modulated radiation therapy (IMRT) plans and volumetric modulated arc therapy (VMAT) and to identify the best IMRT plan for patients with primary mediastinal B-cell lymphoma (PMBCL). Methods A total of 16 patients (8 males and 8 females) with early-stage (Ann-Arbor stage Ⅰ) PMBCL were enrolled in this study, with doses of 45 Gy for primary gross tumor volume (PGTV) and 40 Gy for planning target volume (PTV). Four plans were designed for each patient, consisting of static IMRT (5F-IMRT, 7F-IMRT, 9F-IMRT) and VMAT, and the target dosimetric distribution, normal tissue radiation dose, and efficiency of each plan were evaluated. The difference of dose was analyzed by analysis of variance. Results The mean conformity index (CI) and homogeneity index (HI) for PGTV in 5F-, 7F-, 9F-IMRT and VMAT were 1.01 and 1.10, 1.01 and 1.10, 1.01 and 1.10, and 1.01 and 1.11(P=0.963 and 0.843), respectively, while these two indices for PTV were 1.04 and 1.22, 1.03 and 1.19, 1.03 and 1.17, and 1.08 and 1.14(P=0.964 and 0.969), respectively. The parameters of volume and dose were similar on normal tissue (P=0.192-1.000). The treatment time and number of monitor units in 9F-IMRT were significantly higher than those in other static IMRT plans and VMAT (P=0.000, 0.000), and among these plans, VMAT had the lowest number of monitor units (13 345.0 MU) and the shortest treatment time (5.9 min). Conclusions The target volume coverage of 7F-and 9F-IMRT is better than that of 5F-IMRT and VMAT.For early-stage PMBCL, VMAT is not superior to IMRT in terms of dosimetry, especially with a larger area of low-dose radiation to the breast, but it is highly efficient in practice. Key words: Primary mediastinal large B-cell lymphoma; intensity-modulated radiotherapy; Volumetric-Modulated Arc Therapy; Radiotherapy plan comparison