Epidemiological and Survival Analysis of Primary Intestinal Non-Hodgkin's Lymphoma Patients from SEER Database

Introduction: Gastrointestinal tract is the most common site of extranodal non-Hodgkin’s lymphoma (EN-NHL). Most of the data published so far has been on the gastric NHL and very limited data is available on primary intestinal – Non-Hodgkin’s Lymphoma (PI-NHL). Here, we are presenting the epidemiological and survival data for PI-NHL from the SEER 21 database.

Methods: Data for all the EN-NHL and Intestinal NHL are collected for the period 2000-2015 from the SEER 21 database based on the WHO ICD-O3 classification. PI-NHL data has been extracted from EN- NHL and intestinal datasets and then cross-matched for accuracy of the desired patient subset selection. A total of 9,290 PI-NHL cases common to both the lists were selected and used for analysis. Patients with incomplete staging and survival data were excluded from the survival analysis. Survival analysis variables include gender (male or female), ethnicity (white or non-white), early age of onset (≤ 50 years), late age of onset (>50 years), location (small or large intestine), the staging of the tumor as early-stage (stage 1 and stage 2) or late-stage tumors (stage 3 and stage 4), and history of prior malignancy (first primary tumor or second/later primary tumor). Survival analysis is done using a cox-proportional hazard regression model.

Results: The percentage of PI-NHL of all the intestinal cancers and extranodal non-Hodgkin’s lymphoma is 1.42% (1.40 – 1.45, 95% CI) and 10.52% (10.32 – 10.72, 95% CI) respectively. The demographic and clinical characteristics of the patients are described in Figure 1. In the survival analysis (Figure 2), the risk of overall mortality is higher in the late-onset cancers (HR – 1.16, 1.08 -1.24, P-value<0.001), non-white population (HR- 1.13, 1.05 – 1.22, P-value 0.002) and second or later primary tumors (HR – 1.10, 1.01 – 1.20, P-Value – 0.036). Gender, site, and stage are not significantly related to mortality but the trend towards higher mortality is seen in the late-stage tumor (HR – 1.04, 0.97 – 1.12, P-Value – 0.29).

Conclusion: PL-NHL is a rare type of intestinal malignancy. Our study showed that the risk of overall mortality is higher in late-onset cancer, non-white population, and in second or later primary tumors. Gender, site, and stage are not significantly related to mortality. The analysis was done for overall survival and this may have affected the outcome of the survival variables. Therefore, a survival analysis of cause-specific mortality data will give a more elaborate picture of the relationship between the mortality data and these variables.