Abstract
The purpose of this study was to demonstrate the dosimetric potential of volumetric‐modulated arc therapy (VMAT) for the treatment of patients with medically inoperable stage I/II non‐small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT). Fourteen patients treated with 3D CRT with varying tumor locations, tumor sizes, and dose fractionation schemes were chosen for study. The prescription doses were 48 Gy in 4 fractions, 52.5 Gy in 5 fractions, 57.5 Gy in 5 fractions, and 60 Gy in 3 fractions for 2, 5, 1, and 6 patients, respectively. VMAT treatment plans with a mix of two to three full and partial noncoplanar arcs with 5°–25° separations were retrospectively generated using Eclipse version 10.0. The 3D CRT and VMAT plans were then evaluated by comparing their target dose, critical structure dose, high dose spillage, and low dose spillage as defined according to RTOG 0813 and RTOG 0236 protocols. In the most dosimetrically improved case, VMAT was able to decrease the dose from 17.35 Gy to 1.54 Gy to the heart. The D2cm decreased in 11 of 14 cases when using VMAT. The three that worsened were still within the acceptance criteria. Of the 14 3D CRT plans, seven had a D2cm minor deviation, while only one of the 14 VMAT plans had a D2cm minor deviation. The R50% improved in 13 of the 14 VMAT cases. The one case that worsened was still within the acceptance criteria of the RTOG protocol. Of the 14 3D CRT plans, seven had an R50% deviation. Only one of the 14 VMAT plans had an R50% deviation, but it was still improved compared to the 3D CRT plan. In this cohort of patients, no evident dosimetric compromises resulted from planning SBRT treatments with VMAT relative to the 3D CRT treatment plans actually used in their treatment.PACS numbers: 87.50.‐a, 87.53.‐j, 87.55.‐x, 87.55.D‐, 87.55.dk, 87.55.de
Highlights
Non-small cell lung cancer (NSCLC) accounts for approximately 75%–80% of all patients diagnosed with lung carcinoma
Of the 14 cases, three had a tumor located in the right upper lobe (RUL), two in the right middle lobe (RML), two in the right lower lobe (RLL), five in the left upper lobe (LUL), and two in the left lower lobe (LLL)
The overall dosimetrically best case reduced the dose to the heart from 17.35 Gy in the 3D CRT plan to 1.54 Gy in the volumetricmodulated arc therapy (VMAT) plan
Summary
Non-small cell lung cancer (NSCLC) accounts for approximately 75%–80% of all patients diagnosed with lung carcinoma. [4] RTOG 0236 showed that only 75% of patients treated with this approach avoided severe toxicity, the remaining 25% did not.[7] There have been several efforts to improve upon the avoidance of severe toxicity and to decrease the dose to healthy tissue for SBRT lung cases. These efforts included techniques such as intensity-modulated radiation therapy (IMRT) and conformal arc therapy.[8,9,10]
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