Background Patients with primary Sjögren’s syndrome (pSS) have an increased risk for lymphoma, typically of the indolent mucosa-associated lymphoid tissue (MALT) type. Recent studies also indicate an increased risk of the aggressive diffuse large B cell lymphoma (DLBCL) subtype. It is not known if patient characteristics and risk factors for lymphoma are different in pSS patients developing different lymphoma subtypes.
Objectives To study lymphoma subtype distribution, risk factors for lymphoma and survival after lymphoma diagnosis in a population-based cohort of patients with pSS.
Methods Patients with diagnoses of Sjögren’s syndrome and subsequent lymphoma were identified using the national Swedish Patient register 1964-2007 and the Cancer register 1990-2007 (n=236). Of 226 Sjögren-lymphoma patients with available medical records, 70 fulfilled the AECC criteria for pSS. Detailed clinical data was abstracted from the medical records from the diagnosis of pSS until death or January, 15th, 2012.
Results Most of the 70 pSS-lymphoma patients were female (n=57; 81%). PSS was diagnosed at a mean age of 53 years and lymphoma at a mean of 7.6 years later (range 0-31). Total mean follow-up was 13 years (3-35).
MALT lymphoma (n=24) and DLBCL (n=22) were found in similar proportions (34.3% vs 31.4%). Two of the MALT lymphomas later transformed to DLBCL. Other lymphoma subtypes were present in low numbers. Involvement of the parotid gland was common among the MALT lymphomas (n=18/24; 75%), but not among the DLBCLs (n=2/22; 9%).
Both pSS and lymphoma were diagnosed at an earlier age in MALT than in DLBCL patients (mean age of pSS 47 and 58 years, respectively; p=0.01, and mean age of lymphoma 52 and 67 years, respectively; p<0.005). Previous hypergammaglobulinemia was more common among patients developing MALT lymphoma compared to DLBCL (p=0.04) and prior extraglandular manifestations of pSS were more common in those with DLBCL (p=0.03). The ESSDAI value at pSS diagnosis was similar in both patient groups. Treatment for pSS did not differ between the two lymphoma subtypes.The mean overall survival was 60 months in the DLBCL and 105 months in the MALT lymphoma patients.
Conclusions In this large population-based study we found similar proportions of MALT lymphoma and DLBCL in patients with pSS, and indications of different risk factors for development of the different lymphoma subtypes. MALT lymphoma in pSS occurred in a higher frequency and at an earlier age than reported for MALT lymphoma in the general population (7-8% of B-cell lymphomas, median age of diagnosis 61 years) (1). The mean time from pSS diagnosis to lymphoma was 9.8 years in the DLBCL patients, and the occurrence of DLBCL in pSS may be underestimated in studies with follow-up <10 years.
WHO classification of tumours of haematopoietic and lymphoid tissues, 2008.
Disclosure of Interest None Declared