Epidemiologic trends and survival outcomes in patients with primary digestive system lymphoma in the United States.

Background and aims: Primary digestive system lymphoma (PDSL) is an important entity of extranodal lymphoma, yet updated epidemiologic and survival data are lacking.

Methods: Patients diagnosed with PDSL between 1975 and 2020 were identified from the Surveillance, Epidemiology, and End Results database. Kaplan-Meier analysis estimated survival outcomes. Multivariable Cox regression identified independent risk factors, and nomograms were developed to predict 1-, 3-, and 5-year overall survival (OS) and cancer-specific survival (CSS).

Results: A total of 30,568 patients with PDSL were identified, with 57.9% being male and 80.4% white. The most frequent tumor site was the stomach (48.7%) and diffuse large B-cell lymphoma (DLBCL) was the predominant histologic subtype (45.0%). The overall incidence from 2016 to 2020 was 11.11 per 1,000,000 persons, with a decrease observed in lymphoma rates for the stomach, small intestine, large intestine, and pancreas. Long-term trends showed an initial rise in PDSL incidence, followed by a decline since the 1990s. The median OS across all patients was 103 months, with appendiceal lymphoma showing the highest median OS of 253 months. Factors including diagnosis year, age, sex, race, primary tumor site, histologic subtype, stage, and treatment modalities were significantly associated with OS and CSS. Nomograms achieved C-indices of 0.720 for OS and 0.723 for CSS in the training cohort.

Conclusion: The incidence of PDSL initially increased but has recently declined. Survival for all PDSL patients has improved over time. Nomograms to predict survival for patients with DLBCL exhibited good predictive and discriminating abilities.