Metabolic Tumor Volume Assessed by 18F-FDG PET/CT for the Prediction of Outcome in Patients with Multiple Myeloma

摘要

18F-FDG PET/CT allows the direct measurement of metabolic tumor burden in a variety of different malignancies. The aim of this study was to assess whether metabolic tumor volume (MTV) determined by 18F-FDG PET/CT could be used in the prediction of progression-free and overall survival in multiple myeloma patients. Methods: Forty-seven patients (18 women, 29 men; mean age 6 SD, 63 6 11 y) with stage IIIA disease who had undergone whole-body 18F-FDG PET/CT were retrospectively evaluated. Images underwent a 3-dimensional region-of-interest analysis including all focal lesions with a maximum standardized uptake value . 2.5. The MTV of each lesion was calculated using an automated contouring program based on the standardized uptake value and developed with a threshold of 40% of the maximum standardized uptake value. The total MTV of each patient was defined as the sum of metabolic volume of all focal lesions. Patients were treated and then subjected to a mean follow-up period of 24 mo. Results: In the 47 patients studied, MTV range was 1.3–316.3 mL, with a median of 23.7 mL. A direct, significant correlation was found between MTV and the percentage of diffuse 1/2AQ1_ bone marrow plasma cell infiltration (r 5 0.46, P 5 0.006), whereas hemoglobin levels were inversely correlated with MTV (r 5 20.56, P 5 0.0001). At follow-up, patients who developed progressive disease (n 5 18) showed a significantly higher MTV (74.7 6 19.3 vs. 29.8 6 5.1 mL, P 5 0.009) than patients without progressive disease (n 5 29). Furthermore, patients who died of myeloma (n 5 9) had a significantly higher MTV (123.2 6 30.6 vs. 28.9 6 4.2 mL, P 5 0.0001) than survivors (n 5 38). No differences in age, plasma cell infiltration, M protein, albumin, b2-microglobulin, performance status, International Staging System score, and presence or absence of a bone marrow transplant were found between groups. The MTV cutoff level was determined by receiver-operating-characteristic curve analysis, and the best discriminative value found for predicting progression- free and overall survival was 42.2 and 77.6 mL, respectively. By Kaplan–Meier analysis and log-rank testing, progression-free and overall survival at follow-up were significantly better in patients showing an MTV lower than the cutoff than in those having an MTV higher than the cutoff (x2 5 3.9, P 5 0.04, and x2 5 56.3, P , 0.0001, respectively). Conclusion: The direct measurement of tumor burden obtained by calculating MTV on 18F-FDG PET/CT images may be used in the prediction of progression-free and overall survival in myeloma patients.