Effects of Chemotherapy on Hematological Parameters and CD4(+)/CD8(+) Ratio in Cats with Mediastinal Lymphoma and Seropositive to Feline Leukemia Virus

SIMPLE SUMMARY: Mediastinal lymphoma is the most commonly diagnosed tumor in cats with feline leukemia virus infection (FeLV). The cyclophosphamide, vincristine, and prednisolone (COP) chemotherapeutic protocol is widely used and has achieved high complete-response (CR) rates with a long disease-free interval (DFI), and a long median survival time (MST), with low toxicity. The CD4(+)/CD8(+) ratio is used to assess immunity in retroviral infected cats. This study was performed on 18 FeLV-infected cats with mediastinal lymphoma. The complete blood count, creatinine, alanine aminotransferase, and CD4(+)/CD8(+) ratio were measured four times before treating with chemotherapy in the 1st, 2nd, 3rd, and 4th weeks. The white blood cell (WBC) counts, neutrophils, packed cell volume (PCV), and mean corpuscular volume (MCV) changed, while the CD4(+)/CD8(+) ratio was not found to be significantly different. These results suggested that COP chemotherapy is safe as a treatment for FeLV-infected cats with mediastinal lymphoma. ABSTRACT: The objective of this study was to evaluate the effect of the COP chemotherapeutic protocol on hematological parameters, CD4(+)/CD8(+) ratio, and the mortality of 18 client-owned FeLV-infected cats with mediastinal lymphoma. The complete blood count, creatinine, alanine aminotransferase, and CD4(+)/CD8(+) ratio were measured four times before treating with chemotherapy in the 1st, 2nd, 3rd, and 4th weeks. The white blood cell (WBC) counts at the 1st week were significantly different from the 2nd, 3rd, and 4th inductions (p = 0.0075, p = <0.0001, and p = 0.0271, respectively). The neutrophils at the 1st week were significantly different from the 2nd and 3rd inductions (p = 0.0179, and p < 0.0001, respectively). The packed cell volume (PCV) at the 1st week was significantly differed from the 2nd, 3rd, and 4th induction times (p = 0.0029, p = 0.0006, and p = 0.0029, respectively. The mean corpuscular volume (MCV) at the 1st week was significantly different from the 4th week (p = 0.0145). We found that chemotherapy did not cause any significant change in the CD4(+)/CD8(+) ratio (p-value 0.7407). The Kaplan–Meier curves showed the median survival time (MST) for the cats with a CD4(+)/CD8 ratio of less than 1 after the 1st week of chemotherapy was 134 days. This suggested that COP chemotherapy was a safe treatment for FeLV-infected cats with mediastinal lymphoma.