Primary Renal Lymphoma: Report of 32 Cases—A Retrospective Multicenter PLRG Analysis

<b>Introduction</b>: Primary renal lymphoma is extremely rare, accounting for less than 1% of all lymphomas. <b>Objectives</b>: The aim of this study was to describe a group of patients with primary renal lymphoma diagnosed in hematology and oncology centers aligned with the Polish Lymphoma Research Group (PLRG). <b>Patients and methods</b>: This was a retrospective analysis of adult patients with primary renal lymphoma diagnosed at PLRG centers. <b>Results</b>: Thirty-two patients were diagnosed in seven centers over 24 years (2000-2023). The most common type of lymphoma was diffuse large B-cell lymphoma (DLBCL). The median progression-free survival (PFS) after first-line treatment was 2.1 (95% CI: 1.07-4.18) years, while the median overall survival (OS) was 6.3 (95% CI: 1.82-6.34) years. The median age at diagnosis was 63.3 years old, and 59.4% of the patients were females. In multivariate Cox regression for PFS, only creatinine > 1.5 mg/dL (HR 10.2, 95% CI: 2.08-50.09, <i>p</i> = 0.004) and hemoglobin (Hgb) < 10 g/dL (HR 8.39, 95% CI: 1.88-37.49) were associated with inferior PFS. Patients who achieved complete remission (CR) after first-line of treatment had significantly longer PFS (median 4.18, 95% CI: 2.02-4.18 vs. median 0.73, 95% CI: 0.50-0.79, <i>p</i> = 0.004) and OS (median not reached vs. median 1.49, 95% CI: 0.43-6.33, <i>p</i> = 0.001). Patients treated with nephrectomy had longer OS (median not reached vs. median 5.07, 95% CI: 1.32-5.08, <i>p</i> = 0.05). However, in multivariate Cox regression for OS, only hypoalbuminemia was an independent factor for inferior survival (HR 5.44, 95% CI: 1.12-26.38, <i>p</i> = 0.04). <b>Conclusions</b>: Primary renal lymphoma is an extremely rare type of lymphoma with a poor prognosis. The prognosis may improve with future advances in treatment, including nephrectomy.