Dosimetric and Radiobiological Evaluation of Radiation-induced Pulmonary Toxicity in the Esophageal Malignancy Using VMAT
Sanjib GAYEN1,Shekhar ANAND1, Sumanta MANNA1,Sri Harsha KOMBATHULA1,Sweta SONI1,Akanksha SOLANKI1,Sonal VARSHNEY1,Puneet PAREEK1,
1Department of Radiation Oncology, All India Institute of Medical Sciences, Rajasthan-India DOI : 10.5505/tjo.2021.3352 OBJECTIVE
The incidence of radiation-induced pneumonitis after radiotherapy treatment of esophageal malignancy is of great concern. The study aims to evaluate the feasibility, assessing the risk of radiation pneumonitis (RP) with dosimetric and radiobiological outcomes treated with volumetric modulated arc therapy (VMAT) in esophageal cancer patients.

Twenty patients of esophageal cancer that had received radiotherapy using VMAT in our department were retrospectively analyzed. Each of the patient's treatment plan was analyzed with conformity index (CIRTOG), volume covering 95% isodose line (V95%), isodose line covering 95% of the target (ID95%), dose homogeneity index (DHI), low-dose volume of the organs-at-risks (OARs), normal tissue complication probability (NTCP), and risk factor (RF) of the OARs.

The prescription dose ranged from 45 to 54 Gy. The mean value of CIRTOG, V95%, ID95%, DHI, total MU, and the intensity-modulated radiation therapy ratio was 1.12±0.07, 96.58±2.43%, 95.57±2.48%, 0.92±0.03, 741.50±135.50, and 4.01±0.72, respectively. The median value of NTCP was 0.17. The observed value of RF in the lung and heart was 0.61±0.13 and 0.86±0.43, respectively.

The VMAT technique reduces the toxicity rate of the patient and the dosimetric as well as the radiobiological parameters with the quantitative analysis of dose-volume parameters such as Dmean, V20Gy, RF, and NTCP may be used to assess the probability of post-radiotherapy RP. Keywords : Esophageal cancer; radiation pneumonitis; radiotherapy; VMAT