Dosimetry and Toxicity Comparison of Three-Dimensional Conformal Radiation Therapy and Intensity Modulated Radiation Therapy in Locally Advanced Lung Cancer Across a Large Statewide Quality Collaborative.

Objective: Use of intensity modulated radiation therapy (IMRT) versus three-dimensional conformal external beam radiation therapy (3D-CRT) for definitive chemoradiation therapy (CRT) in locally advanced non-small cell lung cancer (LA-NSCLC) has been associated with decreased late pneumonitis, decreased high dose to the heart (itself associated with improved overall survival), and improved patient quality of life. In a statewide radiation oncology quality consortium, we sought to evaluate the impact of IMRT versus 3D-CRT treatment technique on dosimetry and toxicity.

Methods: From 2012 to 2022, 1746 LA-NSCLC patients meeting inclusion criteria underwent definitive RT (90% CRT) with either 3D-CRT (n = 313) or IMRT (n = 1433) and were enrolled in the Michigan Radiation Oncology Quality Consortium (MROQC) prospective, multicenter statewide initiative. Physician reported toxicity and patient-reported outcomes (PROs) were collected during treatment through 6 months after RT and compared by treatment technique. Inverse probability of treatment weighting (IPTW) was used to account for differences in prognostic factors between IMRT and 3D-CRT patients.

Results: Compared with 3D-CRT patients, IMRT patients had significantly larger PTVs (median 386 cc vs 292 cc; P < .0001) and were more likely to have Stage IIIB disease (34.3% vs 23.0%; P < .0001). After adjustment using IPTW, treatment with IMRT compared with 3D-CRT reduced high dose to the lung (mean V30 Gy 17.9% vs 19.2%; P = .027) and heart (proportion with V40 Gy ≥ 20% 6.4% vs 15.3%; P < .0001). In logistic regression models using IPTW, through 6 months of early follow-up, there were no significant differences between 3D-CRT and IMRT in rates of grade 2+ acute esophagitis (odds ratio [OR] = 1.02; 95% CI, 0.73,1.42; P = .91) and grade 2+ early pneumonitis (OR = 1.62; 95% CI, 0.89, 2.96; P = .11) or in likelihood of a clinically significant decline in PROs.

Conclusions: With late follow-up ongoing, this study supports the continued preferential use of IMRT over 3D-CRT for LA-NSCLC treatment due to improvements in heart and lung doses.