High total metabolic tumor volume in PET/CT predicts worse prognosis in diffuse large B cell lymphoma patients with bone marrow involvement in rituximab era.

Bone marrow involvement (BMI) in diffuse large B cell lymphoma (DLBCL) was naively regarded as an adverse clinical factor. However, it has been unknown which factor would separate clinical outcomes in DLBCL patients with BMI. Recently, metabolic tumor volume (MTV) on positron emission tomography/computed tomography (PET/CT) was suggested to predict prognosis in several lymphoma types. Therefore, we investigated whether MTV would separate the outcomes in DLBCL patients with BMI. MTV on PET/CT was defined as an initial tumor burden as target lesion ≥ standard uptake value, 2.5 in 107 patients with BMI. Intramedullary (IM) MTV was defined as extent of BMI and total MTV was as whole tumor burden. 260.5 cm(3) and 601.2 cm(3) were ideal cut-off values for dividing high and low MTV status in the IM and total lymphoma lesions in Receiver Operating Curve analysis. High risk NCCN-IPI (p<0.001, p<0.001), bulky disease (p=0.011, p=0.005), concordant subtype (p=0.025, p=0.029), high IM MTV status (p<0.001, p<0.001), high total MTV status (p<0.001, p<0.001), and ≥ 2CAs in BM (p=0.037, p=0.033) were significantly associated with progression-free survival (PFS) and overall survival (OS) than other groups. In multivariate analysis, high risk NCCN-IPI (PFS, p=0.006; OS, p=0.013), concordant subtype (PFS, p=0.005; OS, p=0.007), and high total MTV status (PFS, p<0.001; OS, p<0.001) had independent clinical impacts. MTV had prognostic significances for survivals in DLBCL with BMI.