Evaluation of early sequential 18F-FDG PET imaging as a prognostic indicator and predictor of response to platinum and pemetrexed chemotherapy in malignant pleural mesothelioma (MPM)

Abstract

e14534 Background: Recent evidence has suggested that baseline SUV and metabolic response measured on sequential PET scans early in the course of chemotherapy may predict for survival and response to chemotherapy. Methods: Patients with MPM suitable for platinum/pemetrexed chemotherapy were studied. Baseline pre-chemotherapy PET and CT scans were performed with a further PET scan before cycle 2. CT scans were repeated mid-treatment and at the end of 6 cycles. PET response was determined by measuring the change in the maximum and mean SUV, PET Vol (volume of tumor above SUV threshold of 3.5) and Total Lesion Glycolysis (TLG, calculated as PET Vol x SUV Max). Metabolic response (MR), as measured by a 25% drop in SUV Max, SUV Mean, PET Vol and TLG was compared to overall survival (OS) and to subsequent response to chemotherapy on CT. CT scans were read using Modified RECIST criteria and CT response was compared to OS. Results: 21 patients had baseline PET scans of whom 17 had a further PET before cycle 2. 19 patients had CT scans evaluable by Modified RECIST criteria. Baseline SUV Max and SUV Mean were found to predict for OS. Median survival was 17.2 months for patients with SUV Max less than 15 versus 6 months for those with SUV Max greater than 15 (p=0.0193). Median survival was 14.1 months for patients with SUV Mean less than 5 versus 6.5 months for those with SUV Mean greater than 5 (p=0.0681). MR defined by SUV Max, SUV Mean, PET Vol or TLG did not predict for OS. MR on PET correlated poorly with CT response with Kappa values of 0.01, 0.05, 0.15 and 0.31 for MR defined by SUV Max, PET Vol, SUV Mean and TLG respectively. CT response using Modified RECIST criteria correlated significantly with OS. Patients with partial response (PR), stable disease (SD) and progressive disease (PD) had median survivals of 25.6 months, 8.6 months and 4.6 months respectively (p=0.0072) Conclusions: MR measured by SUV Max, SUV Mean, PET Volume and TLG on early sequential PET scans did not correlate with CT assessed response to chemotherapy or OS. Baseline SUV Max >15 and SUV Mean >5 were indicative of poor prognosis. CT response as measured by Modified RECIST criteria correlated significantly with OS. No significant financial relationships to disclose.