The prognostic value of models such as the international prognostic index (IPI) in patients with malignant lymphomas treated with a combination of rituximab, doxorubicin, cyclophosphamide, vincristine, and prednisolone is well established. However, whether these prognostic models apply to patients treated with a combination of tetrahydropyranyl adriamycin, rituximab, cyclophosphamide, vincristine, and prednisolone (R-THP-COP) is unclear. This retrospective analysis included 101 patients with Diffuse large B-cell lymphoma (DLBCL) treated with R-THP-COP. The primary endpoint was overall survival (OS). The secondary endpoints were progression-free survival (PFS), complete response rate (CRR), and effectiveness of risk prediction in the IPI, revised international prognostic index (R-IPI), and National Comprehensive Cancer Network (NCCN)-IPI groups. OS and PFS at 5 years were 67% and 58.9%. CRR was 63.5%. The IPI, R-IPI, and NCCN-IPI predicted the outcomes of patients treated with R-THP-COP. According to the NCCN-IPI, OS and PFS could distinguish four risk groups. In conclusion, the NCCN-IPI is the most effective prognostic tool for identifying patients with poor prognosis, even those treated with R-THP-COP.