An evaluation based on relative treatment intensity in older patients treated with reduced-dose R-THP-COP therapy for diffuse large B-cell lymphoma: A multicenter retrospective cohort study

The number of older patients with diffuse large B-cell lymphoma (DLBCL) is increasing. Although the standard treatment for newly diagnosed younger patients with DLBCL has been established, no consensus has been reached regarding the optimal chemotherapy intensity and regimen for older patients with DLBCL. In addition, no method for evaluating treatment intensity in retrospective studies when different numbers of chemotherapy courses are administered has been elucidated.A multicenter retrospective analysis was conducted to evaluate the outcomes of a reduced-dose R-THP-COP regimen, which included 30 mg/m2 of pirarubicin, in 54 patients with DLBCL who were aged ≥75. To assess treatment intensity, we defined the relative treatment intensity (RTI) as the number of courses administered multiplied by the relative dose intensity (RDI).The estimated four-year overall survival rates (OS) of the patients aged 75-80 and ≥ 80 were 55.1% and 60.6%, respectively. There was no significant difference in four-year OS between these age groups. In our cohort, there was no significant difference in the estimated four-year OS between the patients who received reduced-dose R-THP-COP at an RDI of ≥61% and those that received it at an RDI of <61% (P = 0.35). On the other hand, the patients who received reduced-dose R-THP-COP at an RTI of ≥2.7 exhibited a significantly higher estimated four-year OS than those treated at an RTI of <2.7 (68.5% vs. 28.7%; P < 0.001). Multivariate analysis revealed that the RTI was a significant independent predictor of OS. The cumulative incidence of treatment-related mortality (TRM) at one year was 4.2% and 3.4% in the 75-80 and ≥ 80 age groups, respectively. The cumulative incidence of TRM was significantly worse among the patients with Charlson Comorbidity Index (CCI) scores of ≥2 than among those with CCI scores of 0 or 1.Our study suggests that the reduced-dose R-THP-COP regimen is a suitable treatment option for older patients with DLBCL, especially those with CCI scores of <2. Our study also showed that the RTI may be a valuable tool for assessing treatment intensity in retrospective studies involving older patients.