Adaptive time management for patients who have non-small cell lung cancer and underwent definitive radiotherapy: a dosimetric study of different gap duration scenarios

Purpose The purpose of this study was to evaluate the tumor control probability (TCP), normal tissue complication probability (NTCP) and adaptive time management (ATM) in patients who had non-small cell lung cancer (NSCLC) and underwent radiotherapy with same gap length at different treatment weeks.Material and Methods Twenty patients' definitive radiotherapy treatments, completed in 6.5 weeks, were evaluated retrospectively. Three different scenarios with gaps in 5 fractions at different weeks of treatment (2nd, 4th, and 6th week) were planned. Three ATM models (biologically effective dose (CBED), time-dose-fractionation (CTDF) and in-house developed (CInH)) were calculated for each scenario. TCP and NTCP were calculated and compared with the dose-volume histogram (DVH) of each model.Results TCP was accepted as 100% in uninterrupted treatments. When treatment was interrupted and not compensated with ATM, the highest TCP difference was determined as 23.46% in the 4th week (p<.001). Based on comparisons of ATM models, the lowest TCP decrease was found in CInH. Increasing the fraction size by CInH and CBED provided more TCP improvement than increasing the number of fractions by CTDF.Conclusion The treatment gap to be given in the middle of the treatment is more challenging in terms of tumor control. Adaptive approaches that maintain overall treatment time while increasing fractional dose offer increased TCP.