QS138 - A Population-Based Analysis of Primary Colonic Lymphoma: Patterns of Care and Outcomes

Purpose/Background: Primary colorectal lymphoma (PCL) is a rare malignancy (~1%) with a rising incidence over the last three decades. Despite this increase, no standardized treatment regimen exists, and current management includes combinations of chemotherapy, surgery, and radiation. The aim of this study was to describe patterns of care and outcomes of PCL in a U.S. population-based cohort.

Methods/Interventions: The Surveillance, Epidemiology, and End Results Database was queried to identify adults diagnosed with PCL, 2000-2017. Exclusion criteria were no documentation of treatment, more than one primary cancer, no histologic confirmation of lymphoma, lymphoma of the anal canal, and documentation reported only by nursing home, autopsy, or death certificate. Histology was grouped into diffuse large B cell (DLBCL), follicular, mantle cell, marginal zone, non-Hodgkin’s, and Hodgkin’s lymphoma + other. Treatment was categorized as: surgery (Sx), chemotherapy (CT), surgery + chemotherapy (Sx+CT), radiation + other (RT+other), or no treatment (NT). Tumor location was defined as proximal colon (appendix-transverse), distal colon (splenic flexure-sigmoid), or rectum. Multinomial logistic regression was conducted to identify factors associated with treatment. Cox proportional hazard and competing risk models were used to estimate the effect of treatment on overall (OS) and disease-specific survival (DSS).

Results/Outcomes: Of 4,069 patients, 50% were ≥65 years old, 63% male, and 82% white. Proximal lesions were more common (48%) and DLBCL was the most prevalent histologic subtype (42%). The largest proportion of patients underwent Sx alone (28%); 23% received CT only, 20% had Sx+CT, 24% were NT, and only 5% underwent RT+other. Multinomial analysis showed significant associations between treatment received and age, race, marital status, stage, histology, and lymphoma location. Compared to CT, patients ≥65 years old were less likely to receive any treatment and proximal lesions were more likely to undergo Sx+CT. CT was used at higher rates for more advanced stage disease (Table 1). OS and DSS were 63% and 70% for CT, 65% and 75% for Sx, 71% and 78% for Sx+CT, 72% and 78% for RT+other, and 64% and 74% for NT. After adjustment, factors associated with worse OS were age ≥65, male sex, Black race, rurality, higher stage, and histology, whereas proximal lymphoma was associated with improved OS. NT (hazard ratio [HR] 1.56, 95% confidence interval [CI] 1.35-1.81) and Sx alone (HR1.34, CI 1.17-1.54) were associated with lower OS when compared to CT, while Sx+CT had better prognosis (HR 0.71, CI 0.61-0.83). For DSS, a similar prognostic role of clinicodemographic factors was observed. Particularly, NT (HR 1.36, CI 1.12-1.64) and Sx alone (HR 1.25, CI 1.05-1.49) had worse DSS than CT, while Sx+CT had better outcomes (HR 0.73, CI 0.61-0.87).

Conclusion/Discussion: In this population-based cohort, one quarter of the patients did not receive any treatment, which was associated with increasing age, and worse survival. Patients with proximal lesions were more likely to undergo Sx+CT, with improved prognosis, possibly suggesting that localized disease amenable to surgical resection and systemic treatment may lead to better oncologic outcomes. As with other colorectal cancer, elderly, Black race, and rural setting had worse survival rates, suggesting potential disparities extending to this subset of patients.