FDG-PET parameters as predictors for outcome in non small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT)
Session type: Poster / e-Poster / Silent Theatre session
To identify predictive FDG-PET imaging factors for outcomes following SBRT in early stage NSCLC
Patients with inoperable T1 and T2 NSCLC and a baseline FDG PET-CT at a single centre (St James's University Hospital, Leeds, UK) treated with SBRT for a single tumour between 2009 and 2012 were included. Scans were reported by a single radiologist. Prospective data was collected on a range of FDG-PET parameters (including SUVmax and TLG –Total lesion glycolysis). Patient characteristics and outcome variables including stage, histology, PTV volume, performance status, dose, time interval between PET and SBRT, maximum response to treatment and patterns of failure collected and analysed. The PET parameters were analysed as a continuous variable.
125 patients (72 female, 53 male), median age 75.2. 94 were T1 and 31 T2. Median follow up 1.19 yrs (range 0.28-3.3). Histology was available in 40 patients.
In assessable patients maximal response to treatment was CR in 19%, PR in 50%, SD in 14% and PD in 11%.
Relapse free survival at 2 years was 55%. Local, regional and distant relapse-free rates were 94%, 89% and 83% respectively. Overall and cause-specific survival at 2 years was 57% and 81% respectively.
Median SUVmax was 9.2 in patients who had a relapse and 7.35 in those without. On multivariate analysis, pre-treatment SUVmax predicted for recurrence (p=0.005528), distant metastases (p=0.024081) and overall survival (p=0.000253). This was consistent amongst patients with and without diagnostic pathology. Median SUVmax for patients with and without histology was 5.85 and 7.65 respectively. SUVmax however did not correlate with local or regional relapse.
Stage was a significant predictor for OS and RFS, consistent with previous data. Dose of radiation and time interval from PET to SBRT showed no significant correlation with outcome.Other PET parameters assessed include TLG 20 which correlates with regional relapse, the significance of this is not clear.
This study identifies that SUVmax is the strongest FDG-PET parameter to correlate with outcome following SBRT for NSCLC. This is consistent with previously published data. With SBRT an emerging treatment modality for early stage disease, this may have future implications on the use of adjuvant chemotherapy.