Exhibit Hall | Forum 7
Purpose: : Model-independent predictions of optimal hypofractionated radiotherapy regimens for early stage non-small cell lung cancer (NSCLC).
Methods: A series of radiobiological models were previously developed to model tumor control probability (TCP) as a function of biologically effective dose (BED) for stereotactic body radiotherapy (SBRT) of early stage NSCLC for the AAPM Hypofractionated Treatment Effects in the Clinic (HyTEC) task-force. Amongst those models, the regrowth model that considers TCP as a function of follow-up (F/U) time best described the clinical TCP data, the linear quadratic model (LQ) and universal survival curve (USC) are representative of all other models not considering TCP as a function of F/U time which are indistinguishable. Recent data (2014-2022) after those used for the HyTEC publication from more than 40 published references which include the TCP data from conventional radiotherapy clinical trials were collected to further validate the HyTEC models. Those models’ parameters are used to obtain optimal hypofractionation regimens for early stage T1 and T2 NSCLC.
Results: Given fast proliferating NSCLC cells, a steep dose response for NSCLC is expected with a large α/β ratio. Strong correlations between TCP and BED were observed. TCP increases rapidly with BED and reaches an asymptotic plateau at BED of 90 Gy and 110 Gy for Stage T1 and T2 tumors, respectively. The recent TCP data are well-described by the HyTEC models and further validate the determined model parameters. Fitting the recent TCP data combined with the data used for the HyTEC task-force gave consistent model parameters. Using those model parameters, we determined the optimal hypofractionation regimens for early stage NSCLC in Table 1. Different models yield consistent results.
Conclusion: Optimal model-independent hypofractionated radiotherapy regimens are determined from combined data from previously published radiobiological models. These optimal regimens provide helpful information for clinical practice in treating early stage NSCLC.