Comparison of Changes in Pulmonary Function After Stereotactic Body Radiation Therapy Versus Conventional 3-Dimensional Conformal Radiation Therapy for Stage I and IIA Non-Small Cell Lung Cancer: An Analysis of the TROG 09.02 (CHISEL) Phase 3 Trial

Abstract

The [Anonymized for Review] trial compared conventional radiotherapy (CRT) with stereotactic body radiation therapy (SBRT) in patients with inoperable early-stage non-small cell lung cancer. Patients randomised to SBRT had less local failure and improved overall survival. This analysis reports differences in pulmonary function tests (PFTs) and the six-minute walk test (SMWT) between patients who received SBRT and those who received CRT. We analyzed the PFTs and SMWT of all patients recruited to the [Anonymized for Review] trial. During this trial, patients underwent serial PFTs. Linear regression models were used to compare parameters between SBRT and CRT at 3 and 12-months post-treatment. 101 patients were enrolled, 33 patients were treated with CRT, 61 with SBRT and 7 did not receive treatment. Primary tumor size was similar between arms, SBRT 25mm (SD 9mm) and CRT 28mm (SD 9mm). On regression analysis, at 3 and 12 months, there was no evidence of a difference between arms in PFT decline or distance walked in the SMWT. PTV size was significantly larger in the CRT arm, 142.79 cc (SD 61.14cc) compared to the SBRT group 46.15 cc (SD 23.39 cc). The mean Biological Equivalent Dose (BED) received by the target was significantly larger in the SBRT group 125.92 Gy (SD 21.58 Gy) compared to CRT 65.49 Gy (6.32Gy). Mean dose to the lungs - iGTV was 8.9 Gy (SD 2.34 Gy) in the CRT group and 4.37 Gy (SD 1.42 Gy) in the SBRT group. Despite the considerably higher biologically effective doses delivered to the tumor in SBRT, there was no difference in decline in respiratory function observed between the two groups.