Dosimetric and Clinical Benefits of Conformal Radiotherapy Plus Volumetric Modulated Arc Therapy in the Treatment of Non-small Cell Lung Cancer

Purpose To investigate the dosimetric and clinical benefits of conformal radiotherapy (CRT) plus volumetric modulated arc therapy (VMAT) in the treatment of non-small cell lung cancer (NSCLC). Materials and methods Dosimetric differences, radiation pneumonitis (RP) rates and their correlation were investigated for NSCLC patients treated by CRT, CRT plus VMAT and full course of VMAT, respectively. Results CRT plus VMAT improved the PTV coverage compared with CRT in a cost of higher spinal cord maximum dose (p=0.02), larger lung volume receiving 5 Gy (V5, p=0.02) and mean lung dose (MLD) (p=0.04), and decreased the low dose lung volumes compared with VMAT. The RP rates were 26%, 39% and 49% for CRT, CRT plus VMAT and VMAT, respectively. V5 was significantly associated with RP and had a threshold of 60% and 65% for CRT plus VMAT and VMAT, respectively, to limit the RP rate < 30%. The median three-year overall survival were 17.5, 23.2, 24.5 months for CRT, CRT plus VMAT and VMAT, respectively, without significant difference (p=0.29). Conclusions: CRT plus VMAT is promising in the treatment of NSCLC with improved target coverage compared with CRT and decreased low dose lung volume and RP rate compared with VMAT.