Abstract
Marginal Zone Lymphoma (MZL) is an indolent lymphoma in which the use of PET/CT is poorly explored and also controversial due to the heterogeneous 18F- FDG avidity described in these types of lymphoma. Our aim in the present study is to evaluate the role of 18F-FDG-PET/ CT (PET/CT) in comparison to CT with intravenous contrast enhancement at initial staging and response assessment to chemotherapy in these patients.
A retrospective single-center study that included 34 patients, diagnosed of MZL between 1998 and 2012, with at least one PET/CT available. A total of 55 PET/ CT were performed: 25 at initial diagnosis, 19 for first- line response assessment, 6 in relapse and 5 after relapse- treatment. Locations of involved areas were registered comparing staging CT and PET/CT and were classified as discrepancy or not.
Patients´ baseline characteristics are shown in table 1. At diagnosis, all patients presented with at least one abnormal focal FDG uptake except for one, which reflected a sensitivity of 96%. Median SUVmax was higher in nodal marginal zone lymphoma (NMZL) and extranodal marginal zone lymphoma (ENMZL): 6,1 (4- 8,4) and 6,9 (2- 13,8) respectively, in comparison to splenic marginal zone lymphoma (SMZL) 3,4 (3,2- 3,6) p=0,3. SUVmax was much higher in a patient with histological transformation to a DLBCL (SUVmax 37). Among 17 patients with both radiological imaging at the time of diagnosis, there were 8 patients (47%) with more involved areas demonstrated by PET/ CT than by CT alone, 75% of them were extranodal lesions. PET/CT upstaged 5 patients but in only 2 of them entailed a change in therapeutic management. Four patients did not show FDG avidity by PET/CT in some areas suspected to be involved by CT, what generated a CT sensitivity of 76%.
Patients´ baseline characteristics (N=33). CR: complete remission; PR: partial remission; NA: not assessed; PD: progressive disease.
| . | Patient: n/n available (%) . |
|---|---|
| Age (mean-range) | 61 +/-13’5 |
| Sex Man Woman | . N=17(51%) N=16(48%) |
| WHO diagnosis ENMZL NMZL SMZL | . N=22(66.7%) N=6(18.2%) N=5(15.2%) |
| Imaging techniques at diagnosis CT alone PET/CT alone Both Unknown | . N=6(18.1%) N=7(21.2%) N=18(54.5%) N=2(6.2%) |
| Stage at diagnosis I II III IV | . N=6/33(18.1%) N=5/33(15.1%) N=6/33(18.1%) N=16/33(48.4%) |
| Bone Marrow involvement | N=9/33(27%) |
| Bulky masses | N=3/33(9%) |
| Extranodal disease | N=26/33(78.7%) |
| LDH (median, range) | N=28; 292U/ml (186’5-397’75) |
| Hemoglobine (median, range) | N=29; 118gr/dl (100-134) |
| B2 microglobulin (median, range) | N=24; 3’14mg/dl (2’3-5’1) |
| IPI 0 1 2 3 4 | . N=3/25(12%) N=8/25(32%) N=8/25(32%) N=4/25(16%) N=2/25(8%) |
| First line treatment FCR R-CHOP Rituximab monotherapy Radiotherapy Surgery Spleenectomy | . N=13/33(39.3%) N=5/33(15.1%) N=5/33(15.1%) N=2/33(6%) N=5/33(15.1%) N=3/3 (9%) |
| Response CR PR NA PD | . N=21(63%) N=4(12.1%) N=3(9%) N=5(15.1%) |
| . | Patient: n/n available (%) . |
|---|---|
| Age (mean-range) | 61 +/-13’5 |
| Sex Man Woman | . N=17(51%) N=16(48%) |
| WHO diagnosis ENMZL NMZL SMZL | . N=22(66.7%) N=6(18.2%) N=5(15.2%) |
| Imaging techniques at diagnosis CT alone PET/CT alone Both Unknown | . N=6(18.1%) N=7(21.2%) N=18(54.5%) N=2(6.2%) |
| Stage at diagnosis I II III IV | . N=6/33(18.1%) N=5/33(15.1%) N=6/33(18.1%) N=16/33(48.4%) |
| Bone Marrow involvement | N=9/33(27%) |
| Bulky masses | N=3/33(9%) |
| Extranodal disease | N=26/33(78.7%) |
| LDH (median, range) | N=28; 292U/ml (186’5-397’75) |
| Hemoglobine (median, range) | N=29; 118gr/dl (100-134) |
| B2 microglobulin (median, range) | N=24; 3’14mg/dl (2’3-5’1) |
| IPI 0 1 2 3 4 | . N=3/25(12%) N=8/25(32%) N=8/25(32%) N=4/25(16%) N=2/25(8%) |
| First line treatment FCR R-CHOP Rituximab monotherapy Radiotherapy Surgery Spleenectomy | . N=13/33(39.3%) N=5/33(15.1%) N=5/33(15.1%) N=2/33(6%) N=5/33(15.1%) N=3/3 (9%) |
| Response CR PR NA PD | . N=21(63%) N=4(12.1%) N=3(9%) N=5(15.1%) |
Overall, CR was attained in 24 patients (66%) with 5-y OS 78%. Among 19 patients with a PET/CT available for first-line response assessment, responses were: 12 CR, 2 PR, 1PD and isolated residual lesions in 4 patients. Progression was documented in 2 of the 4 patients with residual lesions which were considered positive, and in 2 patients who maintained remission, the image was interpreted as a false positive (FP). The response assessment was performed by both radiological imaging in 13 patients. Discrepancies were found in 4 cases: CT showed CR in 3 patients while PET/CT detected localized residual disease and in another patient, CT showed stable disease whereas PET/CT demonstrated CR.
Overall, none of the patients in CR by PET/CT relapsed. Five-year OS was 100% in contrast to 64% for those patients with a positive PET/CT after completing treatment (p=0,2), with a mean follow-up of 50 months (10-152). The NPV was 100% and PPV was 71% (5/7).
Relapse was detected in 9 patients (37.5%). Six patients had PET/CT for re-staging and 5 for response assessment. All re-staging PET/CT had FDG-avidity with a median SUVmax of 9.9 (4.6-17.2). PET/CT for response after salvage treatment demonstrated 3 CR and 2 localized residual lesions. The NPV and PPV was 100% and 50%, respectively.
MZL shows higher 18F- FDG avidity in NMZL y ENMZL subtypes. PET/CT is more sensitive than CT at initial staging, chiefly in identifying extranodal involvement. Response assessment PET/CT had a NPV of 100% and PPV of 71 and 50% after first and second-line treatment, respectively.
No relevant conflicts of interest to declare.
Author notes
Asterisk with author names denotes non-ASH members.
