Tumour Control Probability of Stage III Inoperable Non-small Cell Lung Tumours after Sequential Chemo-radiotherapy

Abstract

The aim of this study was to investigate the influence of the duration of waiting time between the end of induction chemotherapy and the start of radiotherapy on tumour control probability (TCP). Patients and Methods: Twenty-three patients with inoperable stage III non-small cell lung cancer (NSCLC) received induction chemotherapy followed by radiotherapy. The mean waiting period between the end of induction chemotherapy and the start of radiotherapy was 80 days; in this period, the median tumour volume increased by a factor of about 6. The Poisson model for TCP and the linear-quadratic model were used to calculate changes in TCP in the waiting time. Results: The 2-year survival of patients treated with curative intent was 8%, lower than the mean value of 26% derived from other studies. Assuming that radiotherapy started on the day of restaging or on the first day of radiotherapy (RT1), the calculated mean TCP at restaging was 13.3% and at RT1 was 0.5% for patients treated with curative intent. Conclusion: The calculated TCP decreased in the waiting period from 13.3 to less than 1%. Hence, the relatively long interval time between chemo- and radiotherapy had a deleterious effect on local control. We recommend the waiting time to be as short as possible.