Introduction

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.

Methods and Materials

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.

Results

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%.

Table 1

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%) 
View Large

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.

Conclusions

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.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
chemotherapy regimen, computed tomography/positron emission tomography imaging, fluorodeoxyglucose f18, marginal zone b-cell lymphoma, extranodal disease, diagnostic imaging, splenic marginal zone b-cell lymphoma, bone marrow involvement, complete remission, diffuse large b-cell lymphoma

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2013 by The American Society of Hematology
2013
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