Prospective Study of Whole Lung Irradiation with Intensity Modulated Radiotherapy/Volumetric Modulated ARC Therapy (IMRT/VMAT) in Patients of Bone and Soft Tissue Ewing Sarcoma with Pulmonary Metastasis

Purpose/Objective(s)

To evaluate the progression free survival and pulmonary failure free survival post Whole Lung Irradiation in patients of bone and soft tissue Ewing sarcoma with pulmonary metastasis and to evaluate the efficacy and early toxicities associated with Cardiac Sparing Whole Lung Irradiation in these patients.

Materials/Methods

In this prospective, interventional, single arm study, we recruited a total of 18 patients with bone and soft tissue Ewing sarcoma with pulmonary metastasis between January 2020 to December 2021. All the patients, after the treatment of primary disease, received Whole Lung Irradiation (WLI) - 18Gy/10#/2 weeks in patients above 18 years of age and 15Gy/10#/2 weeks in those below 18 years of age. All the patients were treated using Image guided IMRT/VMAT technique. Evaluation of pulmonary response was done with NCCT chest at 3 months and 6 months post WLI. Toxicities during and after RT was graded using the CTCAE v.5 criteria. 2-D Echo and PFT values were assessed at 3 months and at 6 months. The quality of life scores were obtained using EORTC QLQ C-30 (version 3) at 4 time points.

Results

Majority of the patients were adults and majority had progression during the study. Only 4 patients had pulmonary relapse as the first site of progression. The 6-month PFS and Pulmonary FFS was 50.8% and 71.4%, respectively. There was statistically significant decrease in FEV1 and FVC values post RT and most patients showed restrictive pattern in PFTs after 6 months of WLI. There was no statistically significant decrease in LVEF or any other cardiac toxicities post RT. The global health QoL scores were significantly reduced at 6 months post RT when compared to pre-RT values. Dmean of heart was 13.1Gy (12.2Gy with a total dose of 15Gy and 14.0Gy with a total dose of 18Gy), which was significantly less compared to conventional planning. No patients had acute or chronic Grade 3 or more toxicities of RT. Only few patients developed Grade 2 toxicities following RT and the proportion of patients showing Grade 2 or more toxicities was significantly less compared to 2-D conventional planning.

Conclusion

This prospective single arm study demonstrated the feasibility and dosimetric advantages (superior cardiac sparing and superior dose coverage of lung volumes) of cardiac sparing whole lung irradiation using VMAT technique. There were no significant severe RT related toxicities and the survival rates were similar to those seen in previous studies. Further studies with greater sample size and longer follow-up will be required to establish the long-term efficacy and safety of this irradiation technique.