A multinational pooled analysis of 434 cases of stage I non-small cell lung cancer (NSCLC) treated with volumetrically image-guided (VIGRT) stereotactic lung radiotherapy (SBRT): Results from the Elekta Collaborative Lung Research Group.

Abstract

7015 Background: Published lung SBRT outcomes/dose response data for inoperable NSCLC come from small phase I-II studies or larger datasets not requiring image-guided radiotherapy (IGRT) or volumetric prescriptions. This entire cohort of SBRT patients had daily online cone-beamCT. Methods: 434 cases of stage I (T1-2N0M0) NSCLC were treated with SBRT via VIGRT at 1 of 5 institutions from 1998-2009. Median age was 74y(42-92); 53% male, 47% female. Median FEV1 was 1.4L(65% predicted); median DLCO was 9.8 ml/min/mmHg(54% predicted). 62% of tumors were biopsy-proven; 84% of cases were staged with CT and PET. Clinical stage was IA in 76%, IB in 22%, locally recurrent in 1%. Median max tumor dimension was 2.4 cm (0.9-8.5cm). Histologies were: 41% adenocarcinoma, 34% squamous, 12% large cell, 13% NSCLC NOS. 8%, 51%, and 42% were grades 1, 2, 3. Median volumetric prescription dose (PD) was 54Gy (20-64Gy) delivered in median of 3 fractions(fx) (1-15fx) over 8d (1-27d). Median biological equivalent PD (BED10) was 132Gy (60-180Gy), equal to 2-Gy fx equivalent (FE) of 110Gy (50-150Gy). Corresponding GTV and PTV mean doses (2-GyFE) were 157Gy and 137Gy. Mean follow-up = 1.3y (0.1-7.3y). Results: 2-y KM rates of local recurrence (LR), regional recurrence (RR) and distant metastasis (DM) were 8%, 13%, and 26%. 2y overall survival (OS) and cause-specific survival (CSS) were 58% and 84%. No statistically significant differences in LR, RR, DM, OS or CSS were identified for biopsied vs. non-biopsied tumors. On univariate analysis, stage (IA 5% v IB 16%, p=0.002), GTV max dimension (<2.7cm 4% v ≥2.7cm 12%, p=0.006), and 2GyFE PD (<88Gy 17% v ≥88Gy 5%, p<0.001) predicted LR. GTV (<115Gy 32% v ≥115Gy 4%, p<0.001) and PTV (<105Gy 24% v ≥105Gy 4%, p<0.001) 2GyFE mean doses also predicted LR. Cox multiple regression confirmed the relationship between PD and LR, independent of GTV size (p=0.01). Conclusions: This is the first Lung SBRT dataset of patients treated uniformly with daily online VIGRT and resulted in excellent local control for stage I NSCLC. A 2-GyFE dose of 88 Gy (BED10 105 Gy) predicted superior local control. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Elekta