Background: Stereotactic body radiotherapy (SBRT) can achieve high tumour control with limited toxicity for inoperable early stage non-small-cell lung cancer (NSCLC) patients.
Patients and methods: The German Epidemiologic Cancer Registries from the Robert-Koch Institute were assessed. Periods according to the availability of SBRT were: (1) 2000-2003 (pre-SBRT); (2) 2004-2007 (interim); and (3) 2007-2014 (broad availability of SBRT). To assess the association of cancer-related parameters with mortality, hazard ratios (HR) from Cox proportional hazards models were computed. To evaluate the change of treatment-related mortality, we performed interaction analyses and the relative excess risk due to interaction (RERI, additive scale) was computed.
Results: A total of 16,292 patients with UICC stage I NSCLC diagnosed between 2000 and 2014 were analysed. Radiotherapy utilization increased from 5% in pre-SBRT era to 8.8% after 2007. In univariate analyses, survival in the whole cohort improved only marginally when 2000-2003 is compared to 2004-2007 (HR 0.92, 95% CI 0.85-1.01) or 2008-2014 (HR 0.93, 95% CI 0.86-1.01). Comparing surgery/radiotherapy, mortality in the radiotherapy group started from a 3.5-fold risk in 2000-2003 to 2.6 after 2007. The interaction analysis revealed a stronger improvement for radiotherapy (multiplicative scale for 2000-2003 vs. > 2007: 0.74, 95% CI 0.58-0.94). On an additive scale, treatment × period interaction revealed an RERI for 2000-2003 vs. > 2007 of - 1.18 (95% CI - 1.8, - 0.55).
Conclusions: Using population-based data, we observed a survival improvement in stage I lung cancer over time. With an increasing utilization of radiotherapy, a stronger improvement occurred in patients treated with radiotherapy when compared to surgery.
Keywords: Lung cancer; Non-small-cell lung cancer; Patterns of care; Population-based analysis; Radiotherapy; Stage I; Stereotactic body radiotherapy.