ESTRO 2023 - Abstract Book

S1077

Digital Posters

ESTRO 2023

PO-1345 Comparison of Lung Doses and Dependent Factors in IMRT, Tomotherapy & 3DCRT Planning of Ca Esophagus

M. Penumur 1 , S. Goswami 1 , B.C. Goswami 1 , D. Choudhury 1 , F.A. Hassan 1 , G. Bora 1 , M. Paul 1 , L. Borah 1 , R. Barauh 1 , D. Saikia 1

1 State Cancer Institute, Gauhati Medical College, Radiation Oncology, Guwahati, India

Purpose or Objective Definitive chemoradiation is the treatment of choice for surgically or medically inoperable patients of esophageal cancer. Intensity Modulated Radiotherapy (IMRT) and Helical Tomotherapy (HT) planning techniques provide better conformality of dose distribution and sparing of organs at risk when compared to Three-Dimensional Conformal Radiotherapy (3DCRT), but with the risk of increased low dose bath. Materials and Methods A total of 28 patients of carcinoma esophagus planned for definitive chemoradiation were recruited from June 2021 till September 2022. Patients were planned for a total dose of 50.4Gy. All patients underwent CT simulation with intravenous contrast, and the treatment volumes and organs at risk were contoured according to RTOG contouring guidelines. Treatment plans of IMRT, HT and 3DCRT were generated for each patient. The lung dose parameters of V20, V30, V5, V10 and Dmean were noted for each plan. Data on location of GTV, volume of GTV and PTV, and craniocaudal length of PTV were the noted factors. The data was compared and analyzed using SPSS software version 28.0.1.0 with Friedman test and Pearson’s correlation test, and a p value of 0.05 was considered as significant. Results The Dmean and V20 lung volumes were similar between IMRT, HT and 3DCRT (Table 1). IMRT and HT had significantly lower V30 when compared to 3DCRT (14 ± 4.3, 12.6 ± 3.4, 19.1 ± 7.1 respectively; p=0.001), whereas V5 (69 ± 18.7, 69.8 ± 19.6, 50.1 ± 15.3 respectively; p=0.001) and V10 (53.6 ± 14.5, 58.4 ± 16.6, 39.9 ± 16.2 respectively; p=0.002) were significantly lower in 3DCRT. All lung dose volumes had significant moderately positive to strongly positive correlation with craniocaudal length of the PTV across the three different techniques (Figure 1). Volume of PTV had no significant correlation with lung dose volumes, whereas volume of GTV had moderately positive correlation with V20 of IMRT (Correlation Coefficient Factor(R)=0.43; p=0.02). IMRT had significantly less low dose region in upper third esophageal tumors (GTV - Gross Tumor Volume) compared to mid and lower thoracic location in V5 (55.1 ± 15.7, 80.2 ± 14.8, 70.2 ± 12.3 respectively; p=0.016), V10 (44.3 ± 12.4, 60.4 ± 13.2, 57.3 ± 11.5 respectively; p=0.017), and Dmean (12.3 ± 3, 16.3 ± 3.3, 14.7 ± 1.1 respectively; p=0.015). HT also had lower V5 (55.5 ± 16.7, 81.3 ± 16.1, 71.8 ± 9.1 respectively; p=0.011), V10 (47.7 ± 12.7, 65.3 ± 17, 66.4 ± 7 respectively; p=0.042), and Dmean (12.5 ± 2.5, 16.5 ± 3.2, 16.3 ± 1 respectively, p=0.01) in upper third esophageal tumors.