Prognostic value of metabolic tumor volume on PET / CT in primary gastrointestinal diffuse large B cell lymphoma

Primary gastrointestinal (PGI) diffuse large B cell lymphoma (DLBCL) is a relatively common disease. Recent studies indicate that measurement of maximum standardized uptake value (SUV(max)) on pretreatment for (18)F-fluorodeoxyglucose PET is an important prognostic factor in PGI DLBCL. However, there is still an association between initial tumor burden and prognosis. Thus, in the present study, we investigated whether tumor volume by PET could have a potential prognostic value to predict the outcome. From 2006 to 2009, 165 Stage I E/II E PGI DLBCL patients were enrolled in the study. One hundred and five patients received cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (R-CHOP) only, whereas 60 patients underwent surgery plus R-CHOP. Metabolic tumor volume (MTV) was defined initial tumor burden as target GI lesion above SUV, 2.5 by PET as a contouring border. Over a median follow-up period of 36.6 months, receiver operating characteristic (ROC) analysis indicated that the best cut-off values for MTV and SUV(max) were 160.1 cm(3) and 12.0, respectively. The estimated area under the ROC curve was higher for MTV than SUV(max). Thus, MTV was a better predictor for survival than SUV(max). In patients with a low MTV (<160.1 cm(3)), there were no significant differences in survival between patients undergoing R-CHOP alone and surgery plus R-CHOP (P = 0.347 for progression-free survival [PFS]; P = 0.148 for overall survival [OS]). Conversely, in patients with a high MTV (>160.1 cm(3)), survival was longer in those who underwent surgery plus R-CHOP than in those treated with R-CHOP alone (P < 0.001 for PFS; P < 0.001 for OS). Multivariate analysis revealed that high MTV is an independent factor for predicting survival. Even in the era of rituximab, treatment of PGI DLBCL is not easy in patients with a high MTV.