MA03.09 Can Clinical Variables be used to Provide Better Follow up in Stereotactic Ablative Radiotherapy (SABR) Treated Lung Cancers?

Abstract

SABR is an established option for medically inoperable peripheral non-small cell lung cancer (NSCLC). The optimal follow up strategy for patients following treatment with SABR has not yet been defined. Delivering follow up requires time and resource from both the patient and the healthcare provider. The aim of this study was to explore time to relapse following SABR and how clinical variables affect Local Control (LC), Progression Free Survival (PFS) and Overall Survival (OS). 1264 patients treated for stage I or IIA NSCLC (May 2009 - August 2018) were included. Medical records were reviewed for baseline characteristics, co-morbidities, treatment and outcomes. Patients were treated according to the UK SABR consortium guidelines. Kaplan Meier analysis with log rank test was used for survival analysis. Statistically significant univariate variables were taken forward into a multivariate Cox Regression Model to correlate clinical variables with outcomes, using IBM SPSS 25. Median age was 74 years with 52% male. Median follow up was 56 months. Median OS was 36 months with 1, 2 and 5 years OS rates of 84.2%, 64.5%, 31.5%, respectively. Median for LC and PFS wasn’t reached. 1, 2 and 5 years LC rates were 98.2%, 95.1%, 92.5%, respectively. 1, 2 and 5 years PFS rates were 87.4%, 78.4%, 72.5%, respectively. The number of total patients who relapsed was 58 and 253 for LC and PFS respectively. Relapse for LC at 1, 2 and 3 year was 27.6%, 70.7% and 89.7% respectively. Relapse for PFS at 1, 2 and 3 year was 53%, 83.4% and 94.9% respectively. Univariate analysis showed Sex, Charlson Co-morbidity score, Age, COPD, performance status, SUV max, FEV1, DLCO, Tumour, Size, Rib Fracture and recurrence were significantly related to OS. Multivariate analysis showed that being male (HZ 1.323 1.077 1.625), having reduced DLCO (HZ 0.978 0.971 0.985) the presence of post SABR lung fibrosis (HZ 0.543 0.440 0.670), the presence of SABR related rib fracture (HZ 0.184 0.044 0.771) and the development of recurrent disease (HZ 2.161 1.730 2.699) were significantly associated with OS. Our results confirm good LC, PFS and OS in a large real world cohort of elderly patients with multiple comorbidities treated with SABR. Multivariate analysis showed that in our cohort certain variables were associated with reduced OS. If these associations are validated, it may be possible to create risk stratified follow up. Currently we follow patients up for 5 years following lung SABR. Our results suggest that we only identify approximately 10% of relapses by providing the final two years of follow up. We propose that clinical variables could be used to identify patients who were more likely to relapse following SABR thereby allowing healthcare resources to be used more efficiently to provide patient follow up.