Outcomes in stage I non-small cell lung cancer following the introduction of stereotactic body radiotherapy in Alberta, Canada.

Abstract

306 Background: Stereotactic body radiotherapy (SBRT) is a treatment option for patients with Stage I (T1-T2N0M0) NSCLC (non-small cell lung cancer) who decline surgery or are medically inoperable. Case series suggest superior outcomes with lung SBRT compared to conventional radiotherapy and high local control rates. The primary study objective was to describe population outcomes in the initial management of stage 1 NSCLC patients including treatment utilization rates and survival. Methods: Clinical records of patients diagnosed with Stage 1 NSCLC who attended any SBRT clinic in Alberta between 2005 and 2011 were examined with REB approval. These cases were linked to the Alberta Cancer Registry and Provincial Health Administration databases. Clinical, treatment, pre-diagnosis 3M Aggregate Clinical Risk Grouping (ACRG3) scores as a proxy for prevailing patient comorbidity and health services characteristics pertaining to all cases of stage 1 NSCLC between 2005 and 2011 were determined. A cox regression model was constructed to examine the influence of these factors and their interactions on cancer outcomes. Results: 2,146 patients were diagnosed with stage 1 NSCLC. Median patient age was 72 and overall 43.0% of cases had a 1 year pre-treatment ACRG3 score of 10-49. Observed treatment utilization rates; surgery 63.4% (95%CI: 61.4-65.4), conventional RT 9.0% (7.9-10.3%), SBRT 3.6% (2.8-4.4%), chemotherapy 0.8% (0.5-1.4%) and no treatment 23.2% (21.4-25.0%). Median survival ranged from 69.6 months for surgery to 17.0 months if no active treatment was delivered. SBRT had survival outcomes superior to conventional radiotherapy: median survival of 39.4 vs. 23.5 months (p<0.001), despite more patients 69.9% vs 63.0% having an ACRG3-1y of 50 or higher. On multivariate analysis, while accounting for all modeled variables including ACRG3 pre-treatment and compared to patients receiving no active treatment, primary surgical intervention HR= 0.23 (95%C.I.:0.18-0.28) and SBRT HR=0.33 (0.21-0.51) remained most strongly associated with survival.No significant variable interactions (p<0.05) between treatment modality, patient age, pathology diagnosis and ACRG3 scores were demonstrated to impact on survival outcomes. Conclusions: Surgery for Stage I NSCLC patients is associated with the best overall survival. SBRT patients have improved survival over conventional radiotherapy. Improvements in population level outcomes may result from an increased utilization of SBRT in the non-surgical management of stage I lung cancer.