¹¹C-acetate PET/CT predicts 4-year overall survival for patients with newly diagnosed myeloma

Objectives We previously reported that ¹¹C-acetate (ACT) PET/CT is a surrogate imaging marker for metabolic measurement of tumor burden in multiple myeloma (MM). We have prospectively extended our investigation on how this marker could be used to predict the 4-year overall survival (OS) in newly diagnosed MM patients.

Methods From Oct 2009 to Dec 2010, 20 patients (M:13, F:7; mean age=67.0±11.0y) were newly diagnosed of active MM when referred for pretreatment ¹¹C-ACT and ¹⁸F-FDG PET/CT. Diagnosis was by hematological and histological proof, and all had pretreatment serum β2-microglobulin (b2m) level measured within 1 mo before PET/CT. They were followed for a minimum of 4 years or till death. Focal bone lesions (FBLs) were visually assessed on PET. SUV_max of L3 was chosen as the index site to represent generalized marrow activity (GMA) for quantitative assessment of diffuse MM. Kaplan-Meier univariate analysis was used to evaluate the prognostic significance of b2m level and PET/CT parameters including GMA of ¹¹C-ACT, GMA of ¹⁸F-FDG, no. of ¹¹C-ACT-avid FBLs and no. of ¹⁸F-FDG-avid FBLs. The threshold of significant prognostic factor for the prediction of 4-y OS was defined by ROC analysis.

Results Of these 20 MM patients (13 stage I, 3 stage II, 4 stage III by International Staging System), ¹¹C-ACT PET/CT was positive in 18 (90%) and ¹⁸F-FDG in 12 (60%). No patient showed extramedullary lesions. During 4 years of follow-up, 8/20 (40%) patients died. Univariate analysis of the above mentioned parameters identified 2 predictors statistically significant for 4-y OS in these patients: 1. pretreatment GMA on ¹¹C-ACT PET/CT (median OS>4 y vs. 30 mo for GMA≤5 & >5, P<0.05); 2. pretreatment serum b2m level (median OS>4 y vs. 30 mo for b2m≤4.22 & >4.22 ug/ml, P<0.05).

Conclusions ¹¹C-ACT PET/CT has a high sensitivity for detection of active disease in treatment-naïve MM patients, a prerequisite condition for monitoring of treatment. Pretreatment GMA>5 on ¹¹C-ACT PET/CT might predict a poor 4-y OS.