P1.03-015 Assessment of Response of FDG-PET Using Total Lesion Glycolysis (TLG) in NSCLC Patients Treated with Nivolumab: Results of a Pilot Study

Abstract

Recent studies using FDG-PET measure the total volumes of the FDG-avid lesions to represent whole-body total metabolic tumor volume (MTV) demonstrating prognostic significance in NSCLC. Total lesion glycolysis (TLG) is the product of mean SUV and MTV and studies have shown the usefulness of TLG for evaluating treatment response. We decide to preliminarily explore the role of TLG, which combines the volumetric and metabolic information of the FDG-PET, as an early predictor of response to nivolumab in NSCLC patients and to determine whether in these patients TLG could provide a better evaluation of response when compared to RECIST. Between September 2015 and April 2016, we enrolled 15 previously treated advanced NSCLC patients to receive nivolumab 3 mg/kg q2w. The CT-scan and FDG-PET evaluation were performed before starting therapy and after 8 weeks (early evaluation). We compared responses assessed by CT-scan and FDG-PET at 8 weeks according to RECIST 1.1 and TLG parameter respectively. We also performed a CT-scan at 12 weeks to confirm or refute the results of the assessment at 8 weeks. There are no standard cut-offs for the TLG parameter. A ROC curve was used to obtain thresholds for the TLG criteria. The ROC study suggested a TLG value between -76% and +76% to define an SD. We considered a TLG value above +76% to define a PD, while a TLG inferior to -76% was necessary to define a PR. In one patient the evaluation at 8 weeks according to TLG criteria showed PD. The same patient presented SD according to RECIST assessed by CT-scan at 8 weeks. For this patient CT-scan at 12 weeks confirmed PD. In this case the TLG of the FDG-PET early identified the patient's progression better than CT-scan. In other two patients, TLG criteria assessed at 8 weeks identified a PR in contrast with SD according to RECIST assessed by CT-scan at 8 weeks. CT-scan at 12 weeks confirmed PRs for both these patients. Even in these two cases the evaluation of TLG by FDG-PET early recognized patient's responses better than CT-scan. For the remaining 12 patients no differences in terms of responses were observed between RECIST and TLG criteria at 8 weeks when compared to RECIST assessed by CT-scan at 12 weeks. These preliminary results from this small study suggest that TLG criteria could provide an early identification of response to nivolumab in NSCLC patients.