Purpose: We analysed a correlation between pre- to post-treatment primary tumour metabolic volume (PT-MV) reduction on 18F-FDG-PET/CT and survival in non-small cell lung cancer (NSCLC) patients treated with chemoradiotherapy (CRT).
Methods: Sixty consecutive patients with NSCLC stage IIIA-B (UICC 7th edition), treated with chemoradiotherapy, who underwent 18F-FDG-PET/CT at the same institution before and 6 weeks after treatment, were analysed. Different metabolic response values were investigated on their correlation with survival parameters: complete response (100% PT-MV reduction); major response (80-99% PT-MV reduction); moderate response (50-79% PT-MV reduction); minor response (1-49% PT-MV reduction) and non-response (no change or increase in uptake).
Results: From 60 patients, 52 (87%) had repeat PET/CT scans 6 weeks after completion of CRT. Complete metabolic response (CR) was reached in ten (17%), whereas major and moderate metabolic responses occurred in 16 (27%) and 15 (25%) patients, respectively. Four patients (7%) had minor metabolic response. Non-response was documented in seven patients (12%). Median overall survival (MS) for the entire cohort was 17 months (95% CI: 11.9-22.1 months). MS according to the different metabolic response values was as follows: 34 months (95% CI: 0-84.1); 22 months (95% CI: 14.2-29.8); 12 months (95% CI: 0.4-23.6); 11 months (95% CI: 0.2-21.8) and 17 months in patients with complete, major, moderate, minor and non-response (95% CI: 6.7-27.3), respectively (p = 0.008). On multivariate analysis, significant predictors of survival included ECOG performance status (p = 0.035, HR 0.49, 95% CI: 0.25-0.95) as well as complete and major metabolic response as a continuous variable with PT-MV reduction of at least 80% (p = 0.021, HR 0.36, 95% CI: 0.15-0.86). Moderate metabolic response did not correlate with improved outcome (p = 0.522).
Conclusions: In this homogeneous locally-advanced NSCLC single-centre patient cohort, a PT-MV reduction of at least 80% (complete and major metabolic response) following CRT was necessary to significantly improve patient outcome.
Keywords: Chemoradiotherapy; Metabolic response; NSCLC; Overall survival; Primary tumour metabolic volume.