Prognostic implications of metabolic tumor volume on 18F-FDG PET/CT in diffuse large B-cell lymphoma patients with extranodal involvement

1353 Objectives Extranodal involvement in malignant lymphoma is known as one of the poor prognostic factors. However, prognostic factors in the diffuse large B-cell lymphoma (DLBCL) patients with extranodal involvement are not well known. This study was performed to determine which clinical factor or PET parameter could be the best predictor for prognosis of DLBCL patients with extranodal involvement. Methods Nineteen DLBCL patients with extranodal involvement who underwent pretreatment 18F-FDG PET/CT were enrolled. Clinical parameters [age, Ann Arbor staging, Eastern Cooperative Oncology Group (ECOG) performance status, serum LDH level, International Prognostic Index (IPI) score, metabolic complete response (mCR) status] and metabolic PET parameters [nodal metabolic tumor volume (NMTV), extranodal MTV (ENMTV), total MTV (TMTV)] were analyzed for their usefulness in predicting disease specific survival (DSS). Results Ten of 19 patients (52.6%) died during follow-up period (mean, 40.3 months). Non-survivors had higher TMTV than survivors (768.9±778.8 cm3 vs. 158.1±194.0 cm3, p=0.0355). ENMTV was also higher in non-survivors (594.2±738.4 cm3 vs. 83.6±133.1 cm3), but there was no statistical significance (p=0.0573). Optimal cutoff values of NMTV, ENMTV, and TMTV for disease specific survival (DSS) were 2.89, 69.63, and 73.93 cm3, respectively. On univariate survival analysis, ECOG performance status (≥2, p=0.0130), mCR+ status (p=0.0033), NMTV (≥2.89, p=0.0427), ENMTV (≥69.63, p=0.0127), TMTV (≥73.93, p=0.0295) were significant prognostic factors for DSS, whereas other clinical factors including IPI score were not. On multivariate survival analysis, TMTV was the best predicting factor for DSS (HR=14.8; p=0.0289), followed by mCR+ status and ECOG performance status. Conclusions The TMTV on pretreatment 18F-FDG PET/CT could be a powerful prognostic factor for DSS in DLBCL patients with extranodal involvement. Patients with high TMTV, mCR- status, high ECOG performance status are at higher risk of shorter survival.