Dear Editor,

We read with interest the recently published article, “Clinical impact of prognostic nutritional index (PNI) in diffuse large B cell lymphoma” by Go et al. [1]. The authors performed a retrospective analysis of 228 newly diagnosed diffuse large B-cell lymphoma (DLBCL) patients. The median overall survival (OS) was shorter in the low PNI group than in the high PNI group (15.6 months vs. not reached; p < 0.001). A multivariate analysis showed that the PNI was an independent prognostic factor for OS. However, no studies have demonstrated the prognostic value of the PNI in very elderly patients with DLBCL. We therefore investigate the predictive role of PNI in very elderly patients (≥ 80 years of age) with DLBCL.

We retrospectively reviewed 84 very elderly patients who were diagnosed and treated at our hospital from 2007 to 2018. The PNI was calculated as 10 × serum albumin concentration (g/dL) + 0.05 × lymphocyte count (number/mm3). The cutoff value of the PNI was set by the receiver operator characteristic (ROC) curve. The Kaplan–Meier method, a univariate Cox proportional hazards analysis, and a multivariate analysis were used to verify the prognostic impact of each factor, including sex, stage, International Prognostic Index score (IPI), performance status (PS), extra-nodal site involvement (ESI), and soluble IL-2 receptor (SIL2R), albumin and lactate dehydrogenase (LDH) levels on overall survival (OS). Of the 84 patients, 39 were male and 45 were female. The median age was 84 years (range: 80–94 years). The characteristics of the participants are shown in Table 1. The median observation period was 39 months. Sixty-two patients received rituximab-containing chemotherapy regimens as an initial treatment, including R-CHOP (n = 30), R-CVP (n = 26), and rituximab alone (n = 5). Proper dose adjustment was performed according to patients’ clinical status such as age, frailty, and comorbidity. Most patients were treated with R-miniCHOP or 70% dose R-CVP. Twenty-one patients received palliative therapy. The optimal cutoff value of the PNI for 3-year OS was set as 41.3, and 38 and 46 patients were classified into the high and low PNI groups, respectively. As shown in Fig. 1, the Kaplan–Meier curve demonstrated that the low PNI group showed significantly worse 3 year OS (3-year OS: 18.8% vs. 55.9%, p < 0.001). In a multivariate analysis, parameters that were independently associated with worse OS included low PNI (p = 0.03, HR 2.72), PS ≥ 2 (p < 0.001, HR 3.14) and high LDH (p = 0.04, HR 3.09) (Table 2).

Table 1 Baseline characteristics of the study patients
Full size table
Fig. 1
figure 1

Kaplan–Meier curves of overall survival according to the PNI

Full size image
Table 2 Univariate and multivariate analysis for overall survival
Full size table

DLBCL is the most common type of non-Hodgkin lymphoma with a median patient age of 60–70 years [2]. Especially in Japan, where the population is aging, the number of elderly DLBCL patients is increasing. As a global standard, the IPI is widely used as a prognostic score for DLBCL. It is known that age itself is associated with the life prognosis and the IPI includes ≥ 61 years of age as a poor prognostic factor [3]. For elderly patients of ≥ 80 years of age, R-CHOP therapy at a lower dose or with a reduced number of courses is described as a reasonable alternative therapy [4]. In order to reach complete remission, it is necessary to maintain an appropriate treatment intensity and minimize adverse events. Thus, physicians need to take into account multiple factors, including comorbidities, complications, cognitive deficiency, social background, and nutritional status. In this study, the PNI was an independent predictor of the prognosis, while the IPI was not in a multivariate analysis that was adjusted for confounding factors. In addition, a former study revealed that a low PNI was significantly associated with more treatment-related adverse events and early treatment interruption [4]. Furthermore, the PNI can be easily calculated by blood tests at a first visit, which can be helpful for treatment selection at an earlier stage after the diagnosis. Taking these factors into consideration, this simple marker may have an important role in the provision of appropriate treatment for individuals.

Our study indicated that the PNI can be routinely used as an independent prognostic marker for DLBCL patients of ≥ 80 years of age. Additional prospective large-scale studies are needed to clarify the clinical significance of relationship between the PNI and the prognosis of elderly patients with DLBCL.