*Article* **The Use of 18F-FDG PET/CT Metabolic Parameters in Predicting Overall Survival in Patients Undergoing Restaging for Malignant Melanoma**

**Khanyisile N. Hlongwa 1, Kgomotso M. G. Mokoala 1, Zvifadzo Matsena-Zingoni 2, Mariza Vorster 1,3 and Mike M. Sathekge 1,3,\***


**Abstract:** Malignant melanoma is one of the more aggressive cancers in the skin, with an increasing incidence every year. Melanoma has a better prognosis if diagnosed early and survival tends to decrease once the disease has metastasized. Positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) has been used extensively over the past two decades in staging and assessing responses to therapy in patients with melanoma. Metabolic PET parameters have been demonstrated to be independent prognostic factors for progression-free survival (PFS) and overall survival (OS) in different malignancies, melanoma included. In our study, we evaluated the metabolic parameters of 18F-FDG PET/CT (flourodeoxyglucose positron emission tomography/computed tomography) in predicting the overall survival in patients with malignant melanoma who presented for restaging. Metabolic PET parameters (maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG)) of the primary tumor, as well as whole-body MTV and TLG of the metastatic disease, were measured. Survival curves for OS were constructed and mortality rates were determined using the different PET variables. Forty-nine patients who presented for a PET/CT restaging in melanoma were included in this study. We found that non-survivors had significantly higher median MTV (11.86 cm<sup>3</sup> vs. 5.68 cm3; *p*-value = 0.022), TLG (3125 vs. 14; *p*-value = 0.0357), whole-body MTV (53.9 cm<sup>3</sup> vs. 14.4 cm3; *p*-value = 0.0076) and whole-body TLG (963.4 vs. 114.6; *p*-value = 0.0056). This demonstrated that high MTV and TLG values of the primary tumor and whole-body TLG as quantified by 18F-FDG PET/CT were prognostic factors for overall survival. The findings may potentially guide clinicians in decision making and identifying patients with a poorer prognosis.

**Keywords:** 18F-FDG PET/CT (fluorodeoxyglucose positron emission tomography/computed tomography); metabolic parameters; metabolic tumor volume (MTV); total lesion glycolysis (TLG); maximum standard uptake value (SUVmax); oncology; malignant melanoma (MM); overall survival (OS); restaging
