Applying Non-Homogeneous Dose Optimization to Improve Conventionally-Fractionated Radiation Plan Quality in Patients with Non-Small Cell Lung Cancer

Abstract Introduction Non-homogeneous dose optimization (NHDO) is exploited in stereotactic body radiotherapy (SBRT) to increase dose delivery to the tumor and allow rapid dose fall-off to surrounding normal tissues. We investigate changes in plan quality when NHDO is applied to conventionally-fractionated inverse-planned radiation (CF-RT) plans, in patients with non-small cell lung cancer (NSCLC). Methods Patients with near-central NSCLC treated with CF-RT in 2018 at a single institution were identified. CF-RT plans were re-planned using NHDO techniques including normalizing to a lower isodose line, while maintaining clinically acceptable normal tissue constraints and target coverage. Tumor control probabilities (TCP) were calculated. We compared delivered CF-RT plans utilizing homogenous dose optimization (HDO) versus NHDO using Wilcoxon signed-rank tests. Median values are reported. Results Thirteen patients were re-planned with NHDO techniques. PTV coverage by the prescription dose was similar (NHDO: 96% versus HDO: 97%, p=0.3). All normal tissue dose constraints were met. NHDO plans were prescribed to a lower prescription isodose line compared with HDO plans (85% vs 97%, p=0.001). NHDO increased mean dose to the PTV (73 Gy vs 67 Gy), dose heterogeneity, and dose fall-off gradient (p Conclusion In select patients, NHDO principles used in SBRT optimization can be applied to CF-RT. NHDO results in increased tumor dose, reduction in select OAR dose objectives, and maintenance of target coverage and normal tissue constraints when compared to HDO. Our data demonstrate that principles of NHDO used in SBRT can also improve plan quality in CF-RT.