Clinical Features and Outcomes of Primary Colorectal Diffuse Large B-Cell Lymphoma: A Multicenter Retrospective Study.

BACKGROUND: Primary gastrointestinal (GI) diffuse large B-cell lymphoma (DLBCL) is a rare malignancy. Given its rarity, the nature of the disease, particularly those originating in the colorectum, remains poorly defined. AIMS: This multicenter retrospective study analyzed the clinical characteristics and treatment outcomes of primary GI DLBCL, with a focus on colorectal cases. MATERIALS & METHODS: A total of 104 cases of primary GI DLBCL were retrospectively collected from three institutions (2010-2024) and classified into three groups based on the lymphoma's origin. RESULTS: Among 104 patients, 57.7% had gastric, 18.3% small bowel, and 24.0% colorectal DLBCL. Approximately 60% presented with limited-stage disease (Stage I-II). All patients received front-line R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone), achieving a complete remission (CR) rate of 81.0%. The estimated 3-year overall survival (OS) and progression-free survival (PFS) were 91.7% and 91.9%, respectively. Outcomes varied by disease origin, with gastric DLBCL showing the most favorable prognosis and small bowel the poorest (3-year OS 93.9% vs. 69.3%). DISCUSSION: In the colorectal subgroup (n = 25), 84.0% had disease in the ascending colon, and 70.0% had limited-stage disease. Obstructive symptoms were the most common initial presentation. The CR rate after R-CHOP was 80.0%, with estimated 3-year OS and PFS of 86.7% and 72.3%, respectively. While primary tumor resection improved local disease control, it did not confer an OS benefit. During follow-up, 13.5% of patients experienced relapse, most frequently more than 12 months after achieving CR. Relapsed or refractory primary GI DLBCL demonstrated better outcomes than conventional relapsed nodal DLBCL. CONCLUSION: These findings confirm the efficacy of front-line R-CHOP in primary GI DLBCL and suggest that primary tumor resection may be a useful component of treatment for localized primary colorectal DLBCL.