Clinical and prognostic value of tumor volumetric parameters in melanoma patients undergoing F-FDG-PET/CT: a comparison with serologic markers of tumor burden and inflammation.

Background: To investigate the association of tumor volumetric parameters in melanoma patients undergoing F-FDG-PET/CT with serologic tumor markers and inflammatory markers and the role as imaging predictors for overall survival.

Methods: A patient cohort with advanced melanoma undergoing F-FDG-PET/CT for planning metastasectomy between 04/2013 and 01/2015 was retrospectively included. The volumetric PET parameters whole-body MTV and whole-body TLG as well as the standard uptake value (SUV) peak were quantified using 50%-isocontour volumes of interests (VOIs) and then correlated with the serologic parameters lactate dehydrogenase (LDH), S-100 protein, c-reactive protein (CRP) and alkaline phosphatase (AP). PET parameters were dichotomized by their respective medians and correlated with overall survival (OS) after PET/CT. OS was compared between patients with or without metastases and increased or not-increased serologic parameters.

Results: One hundred seven patients (52 female; 65 ± 13.1yr.) were included. LDH was strongly associated with MTV (r = 0.73, p <  0.001) and TLG (r = 0.62, p <  0.001), and moderately associated with SUV (r = 0.55, p <  0.001). S-100 protein showed a moderate association with MTV (r = 0.54, p <  0.001) and TLG (r = 0.48, p <  0.001) and a weak association with SUV (r = 0.42, p <  0.001). A strong association was observed between CRP and MTV (r = 0.66, p <  0.001) and a moderate to weak association between CRP and TLG (r = 0.53, p <  0.001) and CRP and SUV (r = 0.45, p <  0.001). For differentiation between patients with or without metastases, receiver operating characteristic (ROC) analysis revealed a cut-off value of 198 U/l for serum LDH (AUC 0.81, sensitivity 0.80, specificity 0.72). Multivariate analysis for OS revealed that both MTV and TLG were strong independent prognostic factors. TLG, MTV and SUV above patient median were accompanied with significantly reduced estimated OS compared to the PET parameters below patient median (e.g. TLG: 37.1 ± 3.2 months vs. 55.9 ± 2.5 months, p <  0.001). Correspondingly, both elevated serum LDH and S-100 protein were accompanied with significantly reduced OS (36.5 ± 4.9 months and 37.9 ± 4.4 months) compared to normal serum LDH (49.2 ± 2.4 months, p = 0.01) and normal S-100 protein (49.0 ± 2.5 months, p = 0.01).

Conclusions: Tumor volumetric parameters in F-FDG-PET/CT serve as prognostic imaging biomarkers in patients with advanced melanoma which are associated with established serologic tumor markers and inflammatory markers.