Association of Treatment Disparities and Primary Sites with the Survival of Non-Gastric Early-Stage MALT Lymphoma

Abstract

To investigate the association between utilization of radiotherapy and differences in survival among patients with non-gastric early-stage mucosa-associated lymphoid tissue (MALT) lymphoma at different primary sites. A total of 5,995 patients with non-gastric early-stage MALT lymphoma in the Surveillance, Epidemiology, and End Results (SEER) database treated between 2000-2015 were extracted and analyzed. Mediation analyses were conducted to quantitatively determine the proportion of the relationship between OS and primary sites mediated by radiotherapy. Inverse probability of treatment weighting (IPTW) was conducted to control confounding factors affecting treatment choice. After controlling for confounding factors, pulmonary MALT lymphoma was found to have the highest rate of omitted radiotherapy compared to other primary sites, including ocular adnexa, salivary gland, skin and other sites. Multivariate Cox analyses showed that lung MALT lymphoma patients had the lowest 10-year OS rate of 58.3%, while skin MALT lymphoma patients had the highest 10-year OS rate of 81.6%. After balancing confounding factors that potentially affected the choice of radiotherapy using IPTW, differences in utilization of radiotherapy explained a significant portion of the poor prognosis of lung MALT lymphoma (35.6%, P = 0.002) and the favorable prognosis of skin MALT lymphoma (6.1%, P <0.001). Differences in survival among patients with non-gastric early-stage MALT lymphoma at different primary sites are associated with disparities in the utilization of radiotherapy.