PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): One critical finding of RTOG 0617 was that heart dose could impact the early overall survival (OS) of non-small cell lung cancer (NSCLC) patients underwent radiotherapy (RT). Although mixed results were reported in studies trying to confirm this finding, studies all suggested that heart dose should be minimized during radiotherapy planning based on the known adverse effects of RT on vasculature and cardiac function. Intensity-modulated radiotherapy (IMRT) had been demonstrated to decrease the dose to lung and heart compared with 3D conformal radiotherapy. As an extended form of IMRT, volumetric modulated arc therapy (VMAT) is able to achieve similar dosimetric distribution while decreasing MU and treatment delivery time compared with IMRT. The purpose of this study is to investigate the efficacy and safety of VMAT, as well as the association of lung and heart dosimetry with OS in stage III NSCLC patients treated by VMAT.
Materials/Methods: 200 consecutive stage III NSCLC patients treated by VMAT from March 2011 to September 2016 were retrospectively reviewed. OS rates were estimated with the Kaplan-Meier method. The Cox regression model estimated the hazard ratio (HR) and the corresponding 95% confidence interval (CI) for univariate (UVA) and multivariate (MVA) analyses. Multivariate model building was performed using stepwise regression (modification of the forward selection method) techniques utilizing significant univariate factors to avoid over-fitting the model.
Results: There were 174 NSCLC patients enrolled in this study with a median age of 63 years (range from 34-86 y). The 1-,2-,3-and 5-year OS rates were 88.5%,66.5%,50.8% and 33.3%, respectively. with a median OS of 36.9 months (95%CI: 28.9～45.0) for a median followup of 14.77 months. For an average prescribed dose of 55.90±0.50 Gy, the mean dose, V25, V30 and V 50 to heart were 16.0±0.6 Gy, 28.7%±1.5%,25.8%±1.4%, and 8.4%±0.9%, and the mean dose, V5,V10,V13,V20 and V30 to lung were 13.8±0.3 Gy,55.1%±1.5%,40.7%±1.3%,33.2%±1.1%,23.0%±0.7%,and 15.2%±0.4%, respectively. Univariate analysis indicated that V30 of heart was associated with overall OS with a p value of 0.044, no other heart and lung dosimetric parameters was associated with OS. The V13 of lung was associated with acute radiation pneumonia with an RP rate of 9.8%.The dosimetric values of heart and lung were strongly correlated with each other.
Conclusion: VMAT was safe and effective in the treatment of stage III NSCLC patients. Heart dose was associated with OS for stage III NSCLC treated by VMAT.
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