Abstract 2672: Early evaluation of response to Vemurafenib treatment with FDG PET/CT in patients with metastatic melanoma.

Abstract

Abstract Targeted therapy against the V600 mutated form of BRAF is a proven effective therapy for melanoma. Reduction of FDG accumulation on PET/CT studies occurs very rapidly in responding patients. This exploratory study aims to correlate early changes in FDG uptake patterns with treatment outcome in patients undergoing Vemurafenib treatment. Patients treated at our institution were evaluated with PET-CT at baseline and at day 7, 14 and 28 from the start of therapy. Maximal Standardized Uptake Value (SUVmax) and Total Lesion Glycolysis (TLG, mean SUV x lesion volume) were recorded and compared for single lesions in the 4 studies. Patients were then monitored for clinical, laboratory and imaging signs of progression and results correlated to the early PET/CT findings. Fifteen patients have been studied. A total of 87 lesions are available for comparative evaluation. A greater than 30% reduction in SUVmax compared to baseline was seen in 69 lesions at day 7, 76 at day 14 and 75 at day 28. Nineteen lesions showed a greater than 20% increase in FDG uptake between day 14 and 28. Similar results were found when comparing TLG values. Quantitative and visual analysis of PET/CT studies identified 5 patients showing signs of metabolic progression between day 14 and 28 likely indicating early signs of treatment resistance. Three of these patients showed signs of disease progression by other means within 4 months from the beginning of treatment while 2 are still in treatment with 3 months follow-up. Of the 10 patients not showing metabolic signs of progression at day 28, four have progressed between 2 and 9 months from the beginning of treatment, while the remaining 6 are still in treatment and progression free with 2 to 12 months of follow-up. In conclusion, our preliminary results suggest that PET/CT may be a powerful surrogate marker of treatment response to vemurafenib. Sequential monitoring of targeted therapy with PET/CT may be useful in early identification of treatment resistance, aid in tailoring alternative strategies and deserves further investigation. Citation Format: Luigi Aloj, Corradina Caracò, Francesca Di Gennaro, Antonio M. Grimaldi, Ester Simeone, Marcello Curvietto, Corrado Caracò, Nicola Mozzillo, Valter Torri, Paolo A. Ascierto, Secondo Lastoria. Early evaluation of response to Vemurafenib treatment with FDG PET/CT in patients with metastatic melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2672. doi:10.1158/1538-7445.AM2013-2672