The Absolute Lymphocyte Count Is Associated with the Prognosis in Patients with Peripheral T-Cell Lymphoma, Not Otherwise Specified

Introduction

Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of tumors that belong to the category of aggressive lymphomas and are roughly subdivided into specified and not otherwise specified (NOS) types. Clinically, the International Prognostic Index (IPI) has been the effective prognostic model to discriminate the prognosis of patients with PTCL-NOS. Also, Prognostic Index for T-cell lymphoma (PIT) has been proposed, which further modified to the Bologna score (modified PIT, mPIT). However, no simple prognostic marker has been satisfactory in predicting treatment outcomes in patients with PTCL-NOS. In this study, we investigate the association between absolute lymphocyte count at diagnosis and the prognosis of patients with PTCL-NOS.

Methods

As a retrospective study, we searched the Lymphoma Registry of Asan Medical Center and Inje University Sanggye Paik Hospital. From April 2001 to Jun 2016, we identified 131 patients diagnosed with PTCL-NOS initially treated with CHOP or CHOP-like regimens. Patients diagnosed with PTCLs other than PTCL-NOS and primary cutaneous lymphoma were excluded. Event-free survival (EFS) was calculated from the date of diagnosis to the date of disease progression, treatment failure, relapse, or death from any cause. Overall survival (OS) was calculated from the date of diagnosis to the date of death from any cause. Lymphopenia was defined as absolute lymphocyte count < 1000 / μL. The association between clinical characteristics and response was analyzed by the Fisher's exact test. Survival curves were analyzed by the Kaplan-Meier method and compared with the log-rank test.

Results

Among 131 patients, 42 (32.1%) patients showed lymphopenia, 58 (44.3%) patients showed B symptoms, and 46 (35.1%) patients showed bone marrow involvement. The median absolute lymphocyte count was 1392/μL (range, 61-10092/μL). According to the International Prognostic Index (IPI) scores, 33 (25.2%) patients belonged to the low risk group (L), 36 (27.5%) to the low-intermediate risk group (LI), 38 (29.0%) to the high-intermediate risk group (HI), and 24 (18.3%) to the high risk group (H).

In univariate analysis, treatment outcomes including CR, EFS, and OS were associated with lymphopenia, B symptoms, performance status, lactate dehydrogenase, extranodal involvement, Ann Arbor stage, IPI risk group, and the Prognostic Index for T-cell lymphoma (PIT) risk groups. After multivariate analysis, lymphopenia was independently associated with CR (≥1000 vs. <1000, odd ratio [OR]: 2.899, 95% confidence interval [CI]: 1.229-6.841, P=0.015), EFS (≥1000 vs. <1000, hazard ratio [HR]: 0.523, 95% CI: 0.339-0.807, P=0.003), and OS (≥1000 vs. <1000, HR: 0.599, 95% CI: 0.375-0.955, P=0.031). IPI risk group was also associated with CR (L/LI vs. HI/H, P <0.001), EFS (P <0.001), and OS (P <0.001).

Conclusions

Absolute lymphocyte count is an independent prognostic factor for the patients with PTCL-NOS. Lymphopenia (<1000/μL) at diagnosis was associated with worse prognosis of patients with PTCL-NOS. Because the absolute lymphocyte count easily obtained from the initial complete blood count, it seems to be simple prognostic factors to estimate the prognosis of patients with PTCL-NOS. The larger scaled study is warranted to confirm our result.