Abstract
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Introduction: Malignant melanoma is the least common type of skin cancer but the deadliest. The incidence has been increasing yearly and its prognosis is significantly improved if diagnosed early.
Positron emission tomography (PET) with 18F-FDG has been widely used over the past two decades in staging and assessing response 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.
Methods: We evaluated the significance of metabolic parameters with 18F-FDG PET/CT in predicting 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 wholebody MTV and TLG of 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.
Results: Time-dependent receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off values for the prediction of death. The Mann Whitney test was used to compare the median values of the SUVmax, MTV, TLG, MTV whole body and TLG whole body between the survivors and the non-survivors. Survival curves for OS were constructed using the Kaplan-Meier method and the log-rank test was used to determine as mortality rates significant differences between groups of the PET bivariate variables.
Our patient cohort had recurrence in the primary site of disease as well as distant disease. Majority of the patients were upstaged and no further treatment was given. In multivariate and univariate parameters, patients that demonstrated higher MTV and TLG were at higher risk of death. In relation to overall survival, only whole body TLG was significantly associated with OS.
The median (IQR) SUVmax, MTV, TLG, whole body MTV and whole body TLG for the patients were 6.62 (3.1-12.6), 8.06 (2.9-21.0), 19.49 (6.8-118.3), 33.35(10.2-100.2) and 462.89(59.3-1553.3) respectively. Compared to the survivors, non-survivors had significantly higher median MTV (11.86 vs 5.68; p-value=0.022), TLG (31,25 vs 14; p-value=0.0357), whole body MTV (53.9 vs 14.4; p-value=0.0076) and whole body TLG (963.4 vs 114.6; p-value=0.0056).
Conclusions: In this patient cohort that presented for restaging, we found that a high MTV and TLG of the primary tumor and wholebody TLG were prognostic for overall survival. These findings may assist clinicians in evaluating and recognizing patients with a poorer prognosis.
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