Prognostic Impact of Programmed Cell Death-1-Positive Cells on Follicular Lymphoma Patients Might Diminish in the Rituximab Era

Programmed cell death-1 (PD-1) is involved in one of the inhibitory pathways of the B7-cluster of differentiation (CD) 28 family; this pathway is known to be involved in the attenuation of T cell responses and promotion of T cell tolerance. PD-1 is known to negatively regulate T cell receptor-mediated proliferation and cytokine production, lead to alternation in the tumor microenvironment. Carreas et al. (J Clin Oncol. 2009; 27: 1470–1476) examined 100 follicular lymphoma (FL) patients and reported better prognosis in the group that had high levels of PD-1-positive cells. In contrast, in the study performed by Richendollar et al. (Human Pathol. 2011; 42: 552–557), which involved 91 FL patients, high levels of PD-1-positive cells were found to have a poor prognostic impact. Although these studies have shown that high levels of PD-1-positive cells in FL patients influence their prognosis, both studies included patients treated without rituximab, and the prognostic impact of PD-1 positivity in the rituximab-era (R-era) has not yet been elucidated.

We retrospectively analyzed data for 91 FL patients uniformly treated by standard rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy in 5 institutions between 2001 and 2009. The median age of the entire cohort was 58 years (range, 34–85 years), and 46 (51%) of the patients were men. We also collected and examined biopsy specimens for diagnosis with respect to PD-1 positivity. The PD-1-positive cells were counted using computer analysis at the Cancer Institute, Japanese Foundation for Cancer Research.

The FL grade on diagnosis was grade 1 for 34 (37%) patients, grade 2 for 41 (45%) patients, and grade 3 for 16 (18%) patients. The median positivity for PD-1 staining was 16.0% (range, 0.01–51.9%) and was significantly higher in the high beta-2 microglobulin (B2M; at least 3) group (P = 0.009); the men had a high tendency for PD-1 positivity (P = 0.08). After a median follow-up of 29.1 months, the 3-year progression-free survival (PFS) and overall survival (OS) were 61.1% and 88.6%, respectively. Stage 4 FL at diagnosis (P = 0.02) and bone marrow involvement (P = 0.05) resulted in worse PFS, and an Eastern Cooperative Oncology Group (ECOG) performance status of 2–4 (P = 0.04), high Follicular Lymphoma International Prognostic Index (FLIPI; P = 0.02), B symptoms (P = 0.04), and high B2M levels (P = 0.005) worsened OS. Multivariate analysis showed that age over 60 years (P = 0.04) and high B2M levels (P = 0.07) were prognostic factors for PFS. PD-1 positivity was not found to be a prognostic factor with respect to both PFS and OS. Because the addition of rituximab to therapy regimens has altered the clinical course and prognosis of FL, some new prognostic factors have been proposed, and the impact of known prognostic factors has been changing. Rituximab might also have changed the prognosis of FL patients with high levels of PD-1-positive cells.

High levels of PD-1-positive cells were not found to be a prognostic factor in this study, indicating that the prognostic impact of PD-1 positivity might be eliminated in the R-era.

No relevant conflicts of interest to declare.