TY - JOUR T1 - <strong>Prognostic value of volumetric PET parameters at early response evaluation in melanoma patients </strong><strong>treated with immunotherapy</strong><strong/> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 489 LP - 489 VL - 61 IS - supplement 1 AU - Ryusuke Nakamoto AU - Lisa Zaba AU - Jarrett Rosenberg AU - Sunil Reddy AU - Tomomi Nobashi AU - Guido Davidzon AU - Carina Aparici AU - Judy Nguyen AU - Farshad Moradi AU - Andrei Iagaru AU - Benjamin Franc Y1 - 2020/05/01 UR - http://jnm.snmjournals.org/content/61/supplement_1/489.abstract N2 - 489Objectives: Immune checkpoint inhibitors (ICIs) induce a significant antitumor effect in melanoma and other cancer types. However, reliable predictors of response to ICIs are not well established. While it may be difficult to accurately measure tumor size on anatomic imaging, 18F-FDG PET/CT offers the ability to quantify volumetric metabolic parameters of any tumor. The purpose of this study was to investigate the prognostic value of whole-body metabolic tumor volume (MTV) and other metabolic tumor parameters, obtained from baseline PET/CT and first restaging PET/CT scans after the initiation of immunotherapy in melanoma patients. Methods: Eighty-five consecutive melanoma patients (M, 57; F, 28) treated with ICIs who underwent FDG PET/CT scans before and approximately 3 months after immunotherapy from July 2010 to November 2018 were retrospectively enrolled. Metabolic tumor parameters including MTV for all melanoma lesions were measured on baseline and first restaging scans. Cutoff values of PET parameters were chosen based on median values. A Cox proportional hazards model was used for univariate and multivariate analyses of metabolic parameters combined with known clinical prognostic factors associated with overall survival (OS). Results: The median OS time in all patients was 45 months (95% CI 24-45 months). Univariate analysis demonstrated that MTV obtained from first restaging PET/CT scan (MTVpost) was the strongest prognostic factor for OS among PET parameters (P = 0.0010). The median OS in patients with high MTVpost (≥ 23.44) was 16 months (95% CI 12-32 months) as compared with more than 60 months in patients with low MTVpost (&lt; 23.44) (Fig. a). The median OS of patients with CNS involvement was 24 months (95% CI 6 to 25 months) compared with more than 60 months in patients without CNS involvement (Fig. b). A multivariate model including PET parameters and known clinical prognostic factors revealed that MTVpost and the presence of central nervous system lesions were independent prognostic factors for OS (P = 0.031, 0.015, respectively) (Table). Combining the clinical factor (CNS involvement) with MTVpost provided further patient stratification. Specifically, the following 3 risk groups were identified: (1) low risk (n = 30, low MTVpost and absence of CNS lesion); (2) intermediate risk (n = 34, high MTVpost or presence of CNS lesion); and (3) high risk (n = 19, high MTVpost and presence of CNS lesion). The median OS of the low, intermediate, and high risk group were more than 60, 32, and 18 months, respectively (Fig. c). The OS in the high risk group was significantly shorter than that in the low risk group (P &lt; 0.0001), not significantly shorter but marginally significantly shorter than that in the intermediate risk group (P = 0.0762). The OS of intermediate risk group was significantly shorter than that in low risk group (P = 0.0025). One pseudoprogrssion case (1.2%) was seen in this population and classified into the high MTVpost group. Conclusions: Whole-body metabolic tumor volume from PET scan acquired approximately 3 months following initiation of immunotherapy (MTVpost) is a strong prognostic indicator of OS in melanoma patients. Although the possibility of pseudoprogression must be considered whenever evaluating first restaging PET imaging, it only occurred in 1 patient in our cohort.View this table:Results of multivariate analysis for predicting overall survival ER -