Prognostic Relevance of Tumor-Infiltrating T-Lymphocytes on Total Metabolic Tumor Volume-Based Risk Stratification of Patients with Diffuse Large B-Cell Lymphoma

Introduction: This study investigated the prognostic relevance between tumor-infiltrating T-lymphocytes (TIL) in lymphoma tissue and total metabolic tumor volume (TMTV) measured by positron emission tomography/computed tomography (PET/CT) in patients with diffuse large B-cell lymphoma (DLBCL). We further examined the effect of combining these on the predictive efficacy in DLBCL patients receiving R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) or R-CHOP-like chemotherapy. Methods: Newly diagnosed DLBCL patients at the Kameda Medical Center between 2007 and 2019 were retrospectively analyzed. The patients were selected based on data, including baseline PET/CT, flow-cytometry data of biopsied specimens, and the use of R-CHOP or R-CHOP-like regimens. TMTV was defined as the volume of lymphoma-associated lesions with a standardized uptake value of ≥ 2.5 as the absolute threshold. To calculate TMTV, a semi-automatic computer-aided analysis of PET/CT images for TMTV was conducted using the open-source software Metavol (Hokkaido University, Sapporo, Japan). To assess the degree of TIL, mononuclear cells from biopsied specimens stained with monoclonal antibodies, including CD19, CD3, CD4, CD8, and CD45, were measured using a Navios flow cytometer (Beckman Coulter, USA). Results: Among 536 DLBCL patients, 288 were excluded because of insufficient flow cytometry data, while another 140 were excluded due to lacking baseline TMTV measurements. Lastly, 18 patients, who did not receive R-CHOP or R-CHOP-like regimens, were excluded. Ninety patients were enrolled in this study. The median age of the patients was 68 years (range: 36-86). 44% of the patients had a poor risk of revised-international prognostic index (R-IPI) score. After a median follow-up period of 53 months, the five-year progression-free survival (PFS) and five-year overall survival (OS) rates were 69% and 74%, respectively. First, the prognostic value of TMTV was evaluated at baseline. The median TMTV was 302 cm 3 (range: 3-3923 cm 3). The optimal cut-off value, calculated by the receiver operating curve, was 564 cm 3 (area under the curve, 0.701). Using this cut-off value, high TMTV was associated with a significantly worse PFS (hazard ratio [HR] =2.669; 95% confidence interval [CI] 1.209-5.892; p=0.01) and OS (HR=3.845; CI 1.699-8.704; p=0.001, Figure 1). Next, the prognostic value of TIL was assessed. The median percentages of CD3 +, CD4 +, and CD8 + cells within the tumor were 43% (range: 1-91), 23% (range: 0.5-81), and 15% (range: 0.4-41), respectively. Using the median cut-off value for each percentage of T-cell subsets, low percentages of CD3 + and CD4 + cells were associated with worse PFS and OS, but the difference was not statistically significant for PFS (PFS: HR=1.71; CI 0.767-3.81; p=0.18 and HR=1.799; CI 0.808-4.007; p=0.15, respectively; OS: HR=3.045; CI 1.279-7.246; p=0.01, Figure 2, and HR=3.275; CI 1.375-7.803; p=0.007, respectively), while a low percentage of CD8 + cells was not associated with either PFS or OS. (HR=1.33; CI 0.603-2.93; p=0.47, and HR=1.672; CI 0.755-3.699; p=0.2, respectively). The positivity of CD4 + cells was strongly correlated with that of CD3 (Pearson's correlation analysis, r=0.881, p<0.0001). On multivariate analysis, including TMTV, CD3 + TIL, and R-IPI poor risk as variables, TMTV and CD3 + TIL predicted worse OS (HR=2.943; CI 1.133-7.64; p=0.02, and HR=2.753; CI 1.153-6.575; p=0.02, respectively). Finally, a prognostic model, combining TMTV and CD3 + TIL, was constructed. The model demonstrated that patients with low TMTV and high CD3 + TIL had favorable outcomes (5-year OS: 100%), and patients with high TMTV or low CD3 + TIL had an intermediate prognosis (5-year OS: 70%). However, patients with high TMTV and low CD3 + TIL had a poor prognosis with a five-year OS of 41% (Figure 3). Conclusions: This study indicated that baseline high TMTV and low percentages of TIL in DLBCL patients were associated with a worse prognosis. The combination of TMTV and TIL improved the TMTV-based prognostic stratification of DLBCL patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.