Metabolic Tumor Volume Has Potential Clinical Impact Compared with SUVmax in Primary Gastrointestinal Diffuse Large B Cell lymphoma

Primary gastrointestinal (GI) lymphoma is the most commonly involved extranodal site and represents 10–15% of all Non-Hodgkin's Lymphoma cases. Recent studies showed that the prognostic value of early 18F-FDG PET using maximum standardized uptake volume (SUVmax) on pretreatment was important prognostic factor in primary GI diffuse large B cell lymphoma (DLBCL). However, initial tumor burden is still an important subject associated with prognosis even extranodal DLBCL. The purpose of this study was to assess the prognostic impact of metabolic tumor volume (MTV) as tumor burden using by PET scan technique compared with initial SUVmax in primary GI DLBCL.

From April, 2006 to July, 2009, 125 stage IE (58 patients) or IIE (67 patients) primary GI DLBCL patients with localized lymph node involvement were enrolled and assigned to 6 or 8 cycles of R-CHOP therapy. Median follow-up was 36 months. Median age was 62 years (range, 20–79 years). Seventy-four patients were male and remainders were female. Numbers of patients above 60 years were 71. Twenty-five patients had an Eastern Cooperative Oncology Group performance status of more than two. Calculatory system by computer automatically delineated a extranodal target lesions above SUV, 2.5 and MTV of GI lesion was 3-dimensional reconstructed by fusion software. The SUVmax was collected from predominant GI lesion and calculated based on the attenuation-corrected images, the amount of injected 18F-FDG and body weight.

The extranodal sites of GI tract were included stomach and duodenum (64 patients, 51.2%), jejunum (10 patients, 8%), terminal ileum (30 patients, 24%), cecum (7 patients, 5.6%), ascending colon (8 patients, 6.4%), transverse colon (3 patients, 2.4%) and decending colon (3 patients, 2.4%). We used ROC curve analysis. 158.3cm³ was decided as best ideal cut-off value of MTV and 15.5 was decided as the cut-off value of SUVmax. Several factors (age, sex, disease status and IPI score) between high MTV (≥158.3cm³) and low MTV group (<158.3cm³) were not significantly different. However, SUVmax higher in high MTV group than low MTV group (p<0.001). In response by revised International Workshop Criteria, low MTV group had excellent response rates than high MTV group (CR, p<0.001; PR, p=0.014; SD & PD, p<0.001). Moreover, 3-year PFS was higher in low MTV group than high MTV group (low MTV group, 96.7%; high MTV group, 37.1%; p<0.001) and 3-year OS was also higher in low MTV group than high MTV group (low MTV group, 97.8%; high MTV group, 42.9%; p<0.001). The PFS and OS were higher in low SUVmax group (<15.5) than high SUVmax group (≥15.5) (p<0.001, p<0.001, respectively). In univariate analysis, high IPI score is still important prognostic factor for PFS and OS (PFS: HR, 4.181 [1.844-9.478] p=0.001 & OS: HR, 4.300 [1.801-10.263] p=0.001). High MTV and high SUVmax were also poor prognostic factors for PFS and OS (high MTV; PFS: HR, 26.543 [7.923-88.231] p<0.001 & OS: HR, 32.458 [7.579-139.018] p<0.001) (high SUVmax; PFS: HR, 6.998 [2.399-20.418] p<0.001 & OS: HR, 13.976 [3.257-59.979] p<0.001). In multivariate analysis, high MTV group (PFS: HR, 19.850 [5.193-75.870] p<0.001 & OS: HR, 17.918 [3.694-86.904] p<0.001) and high IPI score (PFS: HR, 2.659 [1.136-6.223] p=0.024 & OS: HR, 2.866 [1.175-6.989] p=0.021) were independent prognostic factors for PFS and OS. However, SUVmax had not significant value for survival.

In primary GI DLBCL, high MTV is very important and potential prognostic factor compared with SUVmax for predicting the survival. Therefore, more aggressive treatment strategy would be performed in primary GI DLBCL patients having initial high tumor burden.

No relevant conflicts of interest to declare.