Characteristics and Outcomes of Incidentally Diagnosed Diffuse Large B Cell Lymphoma (DLBCL)

Background Advancements in imaging techniques, diagnostic procedures, and increased routine health care visits are anticipated to lead to a higher number of patients with an incidental diagnosis of cancer, including the most common lymphoma DLBCL. In parallel, multiple cancer early detection (MCED) blood assays are emerging to screen for cancer in asymptomatic, average risk individuals. Assays that use methylated DNA markers (MDM) are of special interest and have been shown to detect evidence of DLBCL in the blood in 80% of DLBCL cases (Witzig TE et al ASCO 2022). While these MDMs are candidates for inclusion in MCED assays, the impact of early detection of lymphoma in general and DLBCL specifically remains controversial. Since the outcomes for patients with an incidental diagnosis of DLBCL have not been previously studied and to give further insight to the early detection question, we investigated clinical characteristics and outcome differences between patients with DLBCL found incidentally and those with symptoms or obvious signs of disease that led them to seek medical evaluation. Methods We conducted a retrospective analysis of newly diagnosed DLBCL patients enrolled into the Molecular Epidemiology Resource (MER) of the University of Iowa/Mayo Clinic Lymphoma Specialized Program of Research Excellence from 2002-2015. We reviewed the medical records of the Mayo component to assign a mode of diagnosis (incidental vs symptomatic). We examined disease characteristics and impact on event-free survival (EFS) and overall (OS) survival according to the mode of diagnosis. EFS was the time from diagnosis to relapse, progression, retreatment, or death from any cause. OS was defined as the time from diagnosis to death from any cause. Results 1140 patients with DLBCL (90.6%), high grade B cell lymphoma (2.4%) or primary mediastinal B cell lymphoma (7.0%) were reviewed; 85 (7.5%) patients presented incidentally (incidental group), while 1055 (92.5%) presented with a lymphoma-related symptom or sign, e.g., palpation of a lump/mass, B symptoms and/or other symptoms caused by the lymphoma such as abdominal pain (symptomatic group). In the incidental group, 67.5% (65/85) of patients were diagnosed after an incidental finding on imaging or diagnostic/surgical procedure, 14.1% (12/85) were diagnosed after an incidental lab finding, and 9.4% (8/85) were diagnosed after a clinical health care professional incidentally identified a lump/mass. Compared to the symptomatic group, patients with incidental diagnosis were older at diagnosis (median age 66 vs 63 years, P=0.01) and more likely to present with an earlier stage I/II (62.4% vs 38.9%, P<0.001). Patients who presented with symptoms were more likely to have ≥ 1 extra-nodal site involvement (29.8% vs 15.5%, P=0.005), elevated LDH level (55.4% vs 40.8%, P=0.01), and high-risk IPI score (13.7% vs 5.9% P=0.03) compared to the incidental group. The median diagnosis to treatment interval (DTI) was significantly longer in the incidental group (21 days, IQR 12-34) compared to the symptomatic group (15 days, IQR 9-24) (P = 0.0014). The median follow-up time was 152.3 months in the incidental group and 123.7 months in the symptomatic group. We observed no difference in early failure rates as measured by failure to achieve event-free status at 24 months (EFS24) for incidentally vs symptomatic diagnosis (25.9% vs 31.9%, P=0.25). There was no difference in EFS between the two groups in univariate (HR=1.08, 95%CI=0.8-1.45) or multivariable analysis adjusted for IPI (aHR=0.97, 95%CI=0.72-1.31). There was also no difference in OS in univariate (HR=0.98, 95%CI=0.72-1.34) or multivariable analysis adjusted for IPI (aHR=0.87, 95%CI=0.64-1.19). Conclusion In this large cohort of aggressive B-cell lymphoma, incidental diagnosis occurred in only 7.5% of cases and these patients had earlier stage, lower IPI score, lower LDH levels and less extranodal involvement. These differences in clinical characteristics did not translate into EFS or OS differences. Our findings are the first to describe presentation and outcomes of incidentally diagnosed DLBCL and provide data regarding what investigators may find with MCED assays. Finding more early stage DLBCL patients with lower tumor burden may influence type of treatment, enable the use of fewer chemotherapy cycles, and avoid symptoms and complications of advanced stage disease such as tumor lysis syndrome and organ compression.