Factors that Influence the Need to Start Adaptive Radiotherapy.

Introduction: Adaptive radiotherapy (ART) is an essential approach to account for anatomical and biological uncertainties. Adaptive radiotherapy is, however, time-consuming, and it is unclear which patients are eligible or when is the best time to start ART. Methods: This prospective study was conducted at Kasr El-Aini Center of Clinical Oncology and Nuclear Medicine, Cairo, Egypt from January 2019 to December 2020. Thirty patients with pathologically proven, limited-stage small cell or stage I-II non-small cell lung cancer who were either not fit for or refused surgery or had stage III disease were recruited and underwent treatment planning to receive 60 Gy on a conventional 3D conformal radiation schedule with platinum-based chemotherapy. All patients underwent computed tomography (CT) planning within 2 and 4 weeks of starting radiation therapy to assess the need for adaptation. Pulmonary function test and echocardiography findings were assessed at the end of treatment and at 3 and 6 months after treatment, and were compared to the baseline. Results: We found a significant reduction in mean value of the planning target volume (PTV) in the CT scans at the second (331 cm Conclusions: Conformity index and esophageal dose constraints can predict the need for adaptation at week 2, whereas baseline pulmonary function parameters and echocardiography can predict the need for adaptation at week 4 of radiotherapy.