Long-term clinical results of early-stage lung cancer patients treated with risk-adapted stereotactic body radiotherapy using LINAC or CyberKnife : A single-institution analysis of more than 400 cases.

Abstract

Purpose: The aim of the study was to evaluate the clinical efficacy and side effects of stereotactic body radiotherapy (SBRT) using a gantry-based linear accelerator (LINAC) or robotic technique in a large cohort of consecutively treated medically inoperable early-stage lung cancer patients.

Methods: Between March 2015 and February 2023, 401 early-stage (T1-2 N0 M0) primary lung cancer patients were treated using either LINACs (Varian VitalBeam® and TrueBeam®; Varian, Palo Alto, CA, USA) or CyberKnife® (Accuray, Madison, WI, USA). Median age was 70 years (range 44-90). Diagnosis was based on biopsy for 37.4% of patients, while pathological confirmation was unavailable due to high risk for 62.6%. ¹⁸F‑fluorodeoxyglucose positron-emission tomography (18-FDG-PET) was part of the pretreatment diagnostic workup in 96% (n = 386) of the total cohort. Tumor stage distribution was T1a in 32 (8%), T1b in 179 (44.6%), T1c in 112 (27.9%), T2a in 67 (16.7%), and T2b in 11 (2.7%) patients. Applied dose schemes were identical for both LINAC and CyberKnife treatments, using risk-adapted doses of 45-60 Gy in 3 to 8 fractions, (biologically effective dose ranging from 86 to 151.2 Gy BED₁₀).

Results: At a median follow-up of 32 months (range 2-104), the crude survival rate was 58%. Median overall survival (OS) was 63 months (95% CI: 51.1-74.8) the 2‑, 3‑, and 4‑year OS rates were 79, 68, and 56%, respectively. Actuarial local control (LC) rates were 94% at 2 years, 90% at 3 years, and 87% at 4 years. Median LC was not reached. Median local progression-free survival (LPFS) and progression-free survival (PFS) rates were 49.5 months (95% CI: 42.8-56.3) and 37 months (95% CI: 31.2.-42.8), respectively. Actuarial 2‑, 3‑, and 4‑year LPFS and PFS rates were 75, 60, and 51% and 66, 51, and 42%, respectively. On multivariate analysis, BED₁₀ ≥ 132 Gy predicted improved LPFS, while earlier tumor stage and better ECOG performance status were associated with improved OS. No grade 3 or higher acute side effects were observed. Grade 3 late side effects occurred in 4 patients (1%), including grade 3 late pulmonary fibrosis in 3 cases and potentially treatment-related grade 3 pneumothorax in 1 patient. Rib fracture was observed in 14 cases (3%).

Conclusion: Clinical results after SBRT at a national comprehensive cancer center demonstrate high LC and LPFS rates and favorable PFS and OS, comparable to published studies. Application of a BED₁₀ of 132 Gy or higher shows a potential benefit in terms of LPFS and may thus be recommended in the absence of conflict with organ at risk constraints. SBRT with either LINAC or CK is proven to be a well-tolerated but still highly effective treatment for the elderly, medically inoperable early-stage lung cancer population.