Does Hispanic Origin Affect the Repartition and Outcome of Marginal Zone Lymphoma?

BACKGROUND

Marginal zone lymphoma (MZL) is a rare indolent lymphoma that represents about 7% of all Non-Hodgkin's lymphoma (NHL). MZL is divided into 3 subtypes with different repartition based on primary anatomical site: 60% extra-nodal (EMZL), 32% nodal (NMZL), and 9% Splenic (SMZL) (CA Cancer J Clin, PMID: 27618563). While asymptomatic MZL is often left untreated, there are no clear guidelines regarding the first-line treatment of each subtype (Future Oncol, PMID: 29260925). Although the survival rate of MZL is superior to other NHL with a 5-year survival of 83-91%, cancer remains a leading cause of death among Hispanics (CA Cancer J Clin, PMID: 7618563; Natl Vital Stat Rep, PMID: 32501203). Our study aimed at establishing the impact of Hispanic origin on the repartition and outcomes of MZL.

METHODS:

Data from the Texas Cancer Registry were utilized including adult patients diagnosed with NHL between 2006-2016. The third edition of the International Classification of Diseases for Oncology (ICD-O-3) was used to select patients diagnosed with MZL and all patient information was de-identified. Standard demographic information and outcomes were obtained and summarized in tables. The significance of variance of categorical outcomes by ethnicity was calculated using Fisher's Exact test or T-test (statistical significance of 5%). Survival time was calculated from the date of primary diagnosis to date of death. Kaplan-Meier curves were used for survival distributions and the significance of variation in median survival with ethnicity was assessed with log-rank testing.

RESULTS AND DISCUSSION

Of the 43166 total cases of NHL, 3529 (8.2%) were MZL, of which 82%(n=2867) were Non-Hispanics (NH) and 18%(n=662) were Hispanics (H). When comparing the number of cases among each subtype of MZL in H vs NH, there were 408 vs 1570 cases of EMZL, 174 vs 1022 cases of NMZL, and 38 vs 275cases of SMZL respectively. The median age at diagnosis was 63.2 for H and 66.7 for NH. Younger age at diagnosis was noted in H compared to NH for EMZL (60.4 vs 65, p<0.001) and NMZL (64.4 vs 66.7, p=0.004). There was no statistical difference between genders. About 51.6% of H was in the 20-100% poverty index bracket compared to 20.1% in NH (p< 0.0001). The most prevalent insurance type was Medicare in both groups (H: 37%, NH: 47.2%) and the uninsured rate was higher in H (12.4 vs 3.2 p<0.02). Most individuals regardless of their ethnicity lived in the metro area (87%), non-border area (85%). EMZL was more prevalent in H (61% vs 54%, p=0.001) whereas NMZL (26,2% vs 35,6%, p=0.0005) and SMZL (5.7% vs 9.5% p=0.002) where more prevalent in NH.

Regarding systemic treatment, there was no statistically significant difference between the two groups irrespective of MZL subtype; patients were treated with single or multiple agent chemotherapy as it follows: NMZL 34% H vs 27% NH, EMZL 16% H vs 15.5 NH, SMZL 24% H vs 25% NH. Beam radiation was more frequent in H for both EMZL (20% vs 14.6% p=0.031) and NMZL (3.4% vs 0.2%, p=0.02). Median survival in years was very similar in H vs NH (EMZL: 9 vs 9.3; NMZL: 7.6 vs 7.6; SMZL: 7.3 vs 8.3). Furthermore, there was no statistically significant difference in the overall survival probability for the 10-year follow up period (EMZL: p=0.46, NMZL: p=0.69; and SMZL: p=0.74). Demographics and results are summarized in Table 1.

CONCLUSION

Despite differences in demographics, poverty index, insurance coverage, and prevalence of each subtype of MZL in H compared to NH, there was no statistically significant difference in overall survival probability. These findings also suggest that the complex correlation between MZL biology, ethnicity and oncologic care can serve as the equalizer of disparities that lead to long term balanced outcomes. More in depth studies are needed to further clarify.

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