Incidence and Survival Rates of Primary Ocular Lymphoma: A Population-Based Study

Primary ocular lymphoma (POL) is a rare lymphocytic malignancy of predominantly B-cell origin of primary central nervous system.¹ It represents 4% to 6% of all primary central nervous system tumors and 1% to 2% of extranodal lymphomas.^2,3 The tumor can arise from any part of the eye: retina, uvea, vitreous, Bruch membrane, and optic nerve.^1,3

Although this type of tumors is rare, its incidence has increased over the past years.³ Recent studies have reported an increase in the incidence of POL from 0.027/100,000 in 1973 to 1/100,000 in the early 1990s in the United States.^1,3,4 The increase in the incidence has been hypothesized to be linked to the increased number of immunosuppressed and immunodeficient individuals, increased life expectancy, and improvement of diagnostic tools.^1,4 Few reports studied the prognostic factors of the tumor.^2,5 They found that individuals aged ≥60 years, diffuse large B-cell type lymphoma, and nonconjunctival tumors were all associated with poorer survival rate.^2,5 Liu and Zheng⁵ used the Surveillance, Epidemiology, and End Results (SEER) database for the period between 1973 and 2014 to study POL. They found that the incidence was 0.48/100,000 individuals. Moreover, the 10-year overall survival for patients aged ≥60 years compared with younger patients was 36.2% and 75.8%, respectively.⁵ We aimed in this study to explore the updated incidence and survival rates of POL.

This was a secondary analysis of publicly available data from the SEER database (2000–2018). Therefore, ethical approval was waived for this study. The age-adjusted incidence rate (AAR) was calculated for the total population, and based on age, sex, race, ethnicity, year of diagnosis, and histology. Furthermore, the overall survival rates were calculated for the total population and based on the selected population characteristics.

Table 1 summarizes the patients’ AAR. Out of the 3437 patients, 1518 were males (44.2%) and 1919 were females (55.8%), with an overall AAR of 0.206/100,000 individuals. When stratifying the AAR by year, we noticed a slight, stable reduction over the recent years (0.206 in 2000 to 0.167 in 2018, Supplementary Digital Content Table 1, https://links.lww.com/APJO/A169). Similarly, we observed a stable reduction in the AAR in 2000 to 2008 as compared with 2009 to 2018 (0.235 vs 0.184). While the majority of individuals were under 60 years of age (38.6%), individuals aged ≥70 years had a higher AAR (0.92 vs 0.094 per 100,000). The AAR was higher in Asian or Pacific Islander (0.248) and White patients (0.202) as compared with Black (0.15) and American Indian/Alaska Native patients (0.078). Conjunctival tumors accounted for 941 cases (27.4%) with an AAR of 0.057/100,000. Stratifying by histology, we found that mucosa-associated lymphoid tissue lymphoma was the most reported type (55.8%) followed by diffuse large B-cell type lymphoma, (12.3%) with an AAR of 0.115 and 0.025 per 100,000, respectively (Supplementary Digital Content Table 2, https://links.lww.com/APJO/A170). We found that old age, race, and tumor site influenced survival rates, with individuals <60 years of age achieving 96.9% 5-year survival rate compared with 91.1% and 88.6% for individuals between 60 and 69 and 70 and older, respectively (Supplementary Digital Content Table 3, https://links.lww.com/APJO/A171). Asian or Pacific Islander patients had the least 5 years survival rates. The conjunctival tumors had a 100% 5-year survival rate compared with other tumor sites which ranged from 54.3% to 96.8%.

TABLE 1 - The Age-Adjusted Incidence Rates of Primary Ocular Lymphoma and Rates Stratified to Selected Characteristics, SEER Database Between 2000 and 2018

	Count	%*	Rate†	SE
Total	3437	100	0.206	0.004
Age group (y)
<60	1327	38.609	0.094	0.003
60–69	818	23.8	0.585	0.02
≥70	1292	37.591	0.92	0.026
Sex
Male	1518	44.166	0.199	0.005
Female	1919	55.834	0.212	0.005
Race
White	2692	78.324	0.202	0.004
Black	265	7.71	0.15	0.009
American Indian/Alaska Native	14	0.407	0.078	0.023
Asian or Pacific Islander	390	11.347	0.248	0.013
Unknown	76	—	—	—
Ethnicity
Hispanic	440	12.802	0.202	0.01
Non-Hispanic	2997	87.198	0.207	0.004
Primary Site
C69.0-Conjunctiva	941	27.379	0.057	0.002
C69.1-Cornea, NOS	5	0.145	0	0
C69.2-Retina	10	0.291	0.001	0
C69.3-Choroid	28	0.815	0.002	0
C69.4-Ciliary body	59	1.717	0.004	0
C69.5-Lacrimal gland	434	12.627	0.026	0.001
C69.6-Orbit, NOS	1720	50.044	0.103	0.003
C69.8-Overlapping lesion of eye and adnexa	17	0.495	0.001	0
C69.9-Eye, NOS	223	6.488	0.013	0.001

^*Percent is for total cases.

^†Rates are per 100,000 and age-adjusted to the 2000 US standard population.

NOS indicates not otherwise specified; SE, standard error; SEER, Surveillance, Epidemiology, and End Results.

In this study we observed a slight, stable reduction in the AAR of POL when compared with other studies.^4,5 We assume that the increased adoption of the highly active antiretroviral therapy for human immunodeficiency virus positive patients might explain this trend.⁶ In regards to overall survival, our findings are conforming to that of previous published studies.⁵ Older age, Asian or Pacific Islander race, and nonconjunctival tumors were associated with reduced 5-year survival. Interestingly, our population had a larger female-to-male ratio when compared with other studies.^2,5

In summary, the AAR for POL had a stable reduction over the past years. In addition, we found that survival of POL was affected mostly by old age, Asian or Pacific Islander race, and tumor site.