RESUMO
PURPOSE: A set of treatment planning strategies were designed and retrospectively implemented for locally advanced, non-small cell lung cancer (NSCLC) patients in order to minimize cardiac dose without compromising target coverage goals. METHODS: Retrospective analysis was performed for 20 NSCLC patients prescribed to 60-66 Gy that received a mean heart dose (MHD) ≥10 Gy. Three planning approaches were designed and implemented. The first was a multi-isocentric (MI) volume-modulated arc therapy (VMAT) approach (HEART_MI) with one isocenter located within the tumor and the second chosen up to 10 cm away longitudinally. The second was a noncoplanar (NCP) VMAT approach (HEART_NCP) utilizing up to three large couch angles and a standard arc at couch 0. The final planning strategy took a mixed approach (HEART_HYBRID) utilizing the HEART_NCP strategy for two thirds of the treatment combined with a plan utilizing a pair of opposite-opposed gantry angles for the remaining treatments. Investigational plans were compared to original plans using dose-volume histogram metrics such as organ volume receiving greater than x Gy (Vx) or mean dose (Dmean). RESULTS: Although there was a small but statistically significant decrease in internal target volume coverage for HEART_MI plans and, conversely, a statistically significant increase for HEART_NCP plans, all generated plans met physician-prescribed target constraints. For heart dose, there were statistically significant decreases in all heart metrics and particularly MHD for the HEART_MI (9.8 vs. 15.4 Gy [p < 0.001], respectively), HEART_NCP (9.2 vs. 15.4 Gy [p < 0.001]), respectively), and HEART_HYBRID (7.9 vs. 15.4 Gy [p < 0.001], respectively) strategies. CONCLUSIONS: The strategy providing the best compromise between plan quality and cardiac dose reduction was HEART_NCP, which produced MHD reductions of 37.6% ± 12.9% (6.2 ± 3.4 Gy) relative to original plans. This strategy could potentially reduce adverse cardiac events, leading to improved quality of life for these patients.
