Intensity-Modulated vs 3D Conformal External-Beam Radiation Therapy in Locally Advanced Non–Small Cell Lung Cancer
In a secondary analysis from the NRG Oncology RTOG 0617 trial reported in the Journal of Clinical Oncology, Chun et al found that use of intensity-modulated vs three-dimensional (3D) conformal external-beam radiation therapy was associated with a reduced risk for severe pneumonitis and reduced the radiation dose to the heart in patients with locally advanced non–small cell lung cancer (NSCLC). No significant differences in 2-year overall or progression-free survival were observed with the techniques.
Study Details
In the phase III RTOG 0617 trial, 482 patients received concurrent chemotherapy of carboplatin and paclitaxel with or without cetuximab and radiation doses of 60 Gy vs 74 Gy. Use of intensity-modulated or 3D conformal external-beam radiation therapy was a randomization stratification factor, resulting in balanced use of the techniques in the 60-Gy and 74-Gy groups.
The current secondary analysis compared outcomes among 228 patients receiving intensity-modulated radiation therapy (47%) and 254 patients receiving 3D conformal external-beam radiation therapy (53%). Baseline differences between the intensity-modulated and 3D conformal external-beam radiation therapy groups consisted of a greater proportion of patients in the intensity-modulated group with stage IIIB/N3 disease (38.6% vs 30.3%, P = .056), a greater proportion with positron-emission tomography staging (94.3% vs 88.2%, P = .019), and a smaller proportion who completed high school or had an education beyond high school (P = .01).
Outcomes
Median follow-up was 21.3 months. The intensity-modulated radiation therapy group had larger planning treatment volume (median = 486 mL vs 427 mL, P = .005) and larger planning treatment volume/volume of lung ratio (median = 0.15 vs 0.13, P = .013). There were no differences between the intensity-modulated and 3D conformal external-beam radiation therapy groups in 2-year overall survival (53.2% vs 49.4%, P = .597), progression-free survival (25.2% vs 27.0%, P = .595), local failure (30.8% vs 37.1%, P = .498), or distant metastasis–free survival (45.9% vs 49.6%, P = .661).
Intensity-modulated radiation therapy was associated with a reduced risk of grade ≥ 3 pneumonitis (3.5% vs 7.9%, P = .039), with the reduction in risk remaining significant on multivariate analysis (odds ratio = 0.41, P = .046). Intensity-modulated radiation therapy was associated with a lower volume of the heart receiving radiation doses (P = .049 for volume receiving 20 Gy [V20], P = .003 for V40, and P = .045 for V60); on adjusted analysis, greater volume of the heart receiving 40 Gy was significantly associated with poorer overall survival (hazard ratio = 1.012, P < .001).
The investigators concluded: “[Intensity-modulated radiation therapy] was associated with lower rates of severe pneumonitis and cardiac doses in NRG Oncology clinical trial RTOG 0617, which supports routine use of [intensity-modulated radiation therapy] for locally advanced NSCLC.”
The study was supported by grants from the National Cancer Institute, Bristol-Myers Squibb, and Eli Lilly.
Stephen G. Chun, MD, of the Department of Radiation Oncology at The University of Texas MD Anderson Cancer Center, is the corresponding author of the Journal of Clinical Oncology article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
