Background:

Primary Thyroid Lymphoma (PTL) is a rare disease constituting less than 2% of all extranodal lymphomas; and approximately 2-8% of all thyroid malignancies. In this study, we sought to describe the impact of histologic types on survival.

Methods:

The Surveillance, Epidemiology and End Results (SEER) database was used to identify patients (≥18 years) diagnosed with PTL between 1973 and 2014. B-cell and T-cell lymphomas of all stages were included. Overall survival (OS) was estimated using the Kaplan-Meier method, and compared using Log-Rank test. Cox proportional hazards models were used for adjusted survival analyses.

Results:

Total of 2397 patients were included. Median age was 65 years (56-77); majority were female (n=1734, 72%) and caucasian (n=2178, 91%). Diffuse large B cell lymphoma was the most common histology (DLBCL, N=1351, 56%), followed by marginal zone (MZL, N=334, 14%), follicular (FL, N= 214, 8.9%), Burkitt (BL, N=43, 1.8%), chronic/small lymphocytic leukemia/lymphoma (CLL/SLL, N=41, 1.7%), Hodgkin lymphoma (HL, N=33, 1.4%), T cell lymphomas (TCL, N=14, 0.6%), Lymphoplasmocytic lymphoma (LPL, N=11, 0.4%), and Mantle cell (MCL, N=8, 0.3%). 349 patients (14.6 %) were reported with unclear histology. Total of 1502 (63%) had surgery, 1417 (59%) had chemotherapy and 1153 (48%) had radiation. At a median follow-up of 10.5 years, 1187 (50%) patients died. Median overall survival was 11.4 [10.6-12.3; 95% CI] years. Survival was different by histology type (table, P<0.001). Compared with DLBCL, follicular lymphoma (HR 0.72 [0.57-0.92], P=0.008) and MZL (HR 0.62 [0.48-0.78], P<0.001) were associated with lower mortality, independently of age, sex, race, surgery, chemotherapy, radiation and year of diagnosis. Adjusted mortality decreased by a relative 1% annually (HR 0.99 [0.98-0.99], P<0.001).

Conclusion:

PTL is a rare disease mostly affecting elderly caucasian women. Outcomes vary depending on histologic type. Follicular, MZL and Hodgkin's lymphoma seem to have a favorable prognosis.

Overall Survival by Histology

Histology Number (%) Mean Survival in Years (95% CI) 1-year survival 5-year survival 
DLBCL 1351 (66%) 12.6 [11.7-13.4] 80% 66% 
Burkitt 43 (2.1%) 15.9 [13.5-18.3] 79% 79% 
CLL/SLL 41 (2%) 13 [9.5-16.5] 78% 67% 
Follicular 214 (10.4%) 17.8 [15.1-20.6] 97% 83% 
Hodgkin 33 (1.6%) 25 [20-30] 94% 84% 
LPL 10 (0.5%) 14.2 [7.4-21] 100% 76% 
MZL 334 (16.3%) 13 [11.9-14.1] 95% 83% 
Mantel-Cell 8 (0.4%) 8.7 [3.9-13.5] 87% 56% 
T-cell 14 (0.7%) 10.7 [3.9-17.5] 70% 53% 
Histology Number (%) Mean Survival in Years (95% CI) 1-year survival 5-year survival 
DLBCL 1351 (66%) 12.6 [11.7-13.4] 80% 66% 
Burkitt 43 (2.1%) 15.9 [13.5-18.3] 79% 79% 
CLL/SLL 41 (2%) 13 [9.5-16.5] 78% 67% 
Follicular 214 (10.4%) 17.8 [15.1-20.6] 97% 83% 
Hodgkin 33 (1.6%) 25 [20-30] 94% 84% 
LPL 10 (0.5%) 14.2 [7.4-21] 100% 76% 
MZL 334 (16.3%) 13 [11.9-14.1] 95% 83% 
Mantel-Cell 8 (0.4%) 8.7 [3.9-13.5] 87% 56% 
T-cell 14 (0.7%) 10.7 [3.9-17.5] 70% 53% 

Citation Format: Taha Al-Juhaishi, Victor Yazbeck. Impact of histologic type on survival in primary thyroid lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 596.