Daily Image Guidance With Cone Beam Computed Tomography May Reduce Radiation Pneumonitis in Unresectable Non-Small Cell Lung Cancer

Abstract

Purpose: To investigate the impact of daily image-guided radiation therapy technique on clinical outcomes in patients with inoperable non-small cell lung cancer treated with definitive chemoradiation therapy. Methods and Materials: We compared patients with inoperable non-small cell lung cancer receiving daily cone beam computed tomography (CBCT) after an initial 4-dimensional computed tomography (4DCT) simulation (n = 76) with those receiving daily 2-dimensional orthogonal kilovoltage (kV) imaging (n = 48). The primary endpoint was time to grade ≥2 radiation pneumonitis (RP2), estimated with the cumulative incidence method, compared with Gray's test, and modeled with the Fine-Gray method. Results: Median follow-up was 40.6 months (range, 5.9-58.1 months) for the CBCT group and 75.8 months (range, 9.9-107.8 months) for the orthogonal kV group. Four-dimensional computed tomography simulation was used in 100% (n = 76) of the CBCT group and 56% (n = 27) of the orthogonal kV group (P < .0001). The 1-year cumulative incidence of RP2 was lower in the CBCT group than in the orthogonal kV group (24% vs 44%, P = .020). On multivariate analysis, daily imaging with CBCT after an initial 4DCT simulation was associated with a decreased risk of RP2 (adjusted hazard ratio 0.43, 95% confidence interval 0.22-0.82, P = .011), a finding that persisted among only patients who received 4DCT simulation (adjusted hazard ratio 0.48, 95% confidence interval 0.23-0.98, P = .045). There was no difference in locoregional progression, distant metastasis, any progression, or overall survival between groups. Conclusions: Daily image guided radiation therapy with CBCT compared with 2-dimensional orthogonal kV imaging was associated with a decreased risk of RP2. Clinicians could consider the implications of localization methods during curative intent radiation therapy.