Radiation therapy (RT) is one of the most effective therapeutic modalities for B‑cell non‑Hodgkin's lymphoma of Waldeyer's ring (WR‑B‑NHL). However, the responsiveness of RT remains controversial and clinical biomarkers are required to predict survival in RT‑treated patients with WR‑B‑NHL. Previous studies have suggested an association between RT and systemic immune responses. In the present retrospective study, the lymphocyte to monocyte ratio (LMR) was identified as a systemic immune indicator in RT‑treated patients with WR‑B‑NHL, and the prognostic value of the LMR with RT and systemic immune responses were evaluated. The optimal cut‑off value of the LMR was selected as 3.14, and a high LMR demonstrated improved prognosis and was considered an independent prognostic indicator in RT‑treated patients, particularly in patients with distant non‑irradiated lesions. Furthermore, reverse transcription‑quantitative polymerase chain reaction and ELISA analysis of irradiated lymphoma cell lines and serum samples from patients with WR‑B‑NHL demonstrated the upregulated expression levels of 4‑1BB ligands, calreticulin and high mobility group box 1 compared with non‑irradiated groups. Additionally, CD8+ T cells and expression levels of interferon‑γ in T cells co‑cultured with irradiated cells were significantly increased compared with non‑irradiated cells. The results indicated that the anti‑programmed cell death protein 1 (PD‑1) antibody may serve a role in lymphoma therapy when combined with RT. The results of the present study demonstrated the prognostic significance of the LMR associated with RT in patients with WR‑B‑NHL and acknowledged the potential use of PD‑1 antibody in RT‑treated lymphomas.