# Monocyte and Lymphocyte Count, and Lymphocyte/Monocyte Ratio as Prognostic Factors at the Time of First Relapse in Canine Diffuse Large B-Cell Lymphoma Patients Receiving Chemotherapy

## TL;DR

This study investigated whether monocyte and lymphocyte counts and their ratio at relapse could predict outcomes in dogs with lymphoma undergoing chemotherapy.

## Contribution

The study is the first to evaluate the prognostic value of monocyte and lymphocyte counts and their ratio at relapse in canine diffuse large B-cell lymphoma.

## Key findings

- Monocyte and lymphocyte counts and their ratio at relapse were not significant predictors of survival in dogs with lymphoma.
- Lymphocyte counts during treatment may help identify disease progression.
- Blood cell counts varied significantly at different stages of chemotherapy.

## Abstract

Canine lymphomas account for the majority of haematopoietic tumours in veterinary clinical practice. Several prognostic factors have been evaluated in dogs with diffuse large B-cell lymphoma (DLBCL) and, more recently, the role of leukocytes has been of increased interest. The main objective of this study was to assess the prognostic value of absolute monocyte and lymphocyte count, as well as lymphocyte-to-monocyte ratio (LMR), at the time of first relapse in a population of dogs with diffuse large B-cell lymphoma treated with CEOP-based chemotherapy. Additionally, absolute monocyte and lymphocyte count, as well as LMR, were evaluated for their prognostic value at the time of diagnosis and throughout different timepoints during the course of the chemotherapy treatment. Monocyte counts, lymphocyte counts, and their ratio were not found to be significant predictors of overall survival at relapse or at the time of diagnosis in this population of dogs. Furthermore, our findings suggest that monitoring of the absolute lymphocyte count throughout chemotherapy treatment and during follow-up in these dogs may be of clinical help to identify disease progression. Larger, controlled prospective studies evaluating blood cell counts throughout the course of chemotherapy and at relapse are needed to evaluate these findings further.

Background: Canine lymphoma comprises the majority of haematopoietic malignancies in veterinary clinical practice. Several prognostic factors have been studied and, more recently, there has been an increased interest in the role of the lymphocyte-to-monocyte ratio (LMR) for its prognostic value. To date, the prognostic value of absolute monocyte and lymphocyte counts as well as LMR at the time of relapse in dogs with diffuse large B-cell lymphoma has not been evaluated. The purpose of the present study was to investigate whether the absolute monocyte, lymphocyte or LMR at relapse can predict clinical outcomes for relapsed diffuse large B-cell lymphoma dogs treated with chemotherapy. Additionally, the parameters were evaluated for their prognostic value at the time of diagnosis and throughout different timepoints during the course of their first-line chemotherapy treatment. Materials and Methods: We retrospectively analysed data from 50 dogs with relapsed diffuse large B-cell lymphoma, treated with a CEOP-based first-line chemotherapy protocol. Lymphocyte and monocyte count and LMR were evaluated at different timepoints: at diagnosis, during chemotherapy and at the time of relapse. Overall survival time (OS) and disease-free interval (DFI), as well as overall survival time from relapse (OSr), were measured. Friedman nonparametric ANOVA was used to compare blood cell counts at different timepoints. Spearman rank correlation was used to test for association between blood cell count at various timepoints with the duration of remission and survival time. Results: Monocyte and lymphocyte counts and LMR at the time of first relapse were not found to be adverse prognostic factors for OSr in this population of dogs. Monocyte and lymphocyte counts differed significantly between different timepoints during the chemotherapy protocol. Conclusions: Absolute monocyte and lymphocyte counts and LMR at the time of relapse were not found to be prognostic indicators of OSr in this population of dogs with multicentric lymphoma. Additional studies evaluating absolute monocyte and lymphocyte counts during chemotherapy treatment and following completion of chemotherapy in larger population of dogs are needed to assess whether these counts have clinical utility in detecting disease progression.