Introduction

Hematology is a key tool and discipline in oncology. Hemograms are collected as part of routine work up and staging in all cancer patients to determine if any hematologic abnormalities are present either as a complication to cancer, as a paraneoplastic condition, as part of other disease, or to identify neoplastic cells. In addition, hemograms are performed as part of Standard of Care (SOC) prior to and during chemotherapy and other treatment modalities to evaluate adverse hematologic effects as defined in the most recent Veterinary Comparative Oncology Group publication, VCO, 2016.

Common hematologic abnormalities include anemia, thrombocytopenia, leukopenia and paraneoplastic conditions such as immune-mediated thrombocytopenia (IMT) and immune-mediated hemolytic anemia (IMHA).

Baseline evaluation and later monitoring of hemostatic abnormalities is not routine or part of SOC despite the fact that up to 83% of canine cancer patients have been reported to show abnormal coagulation tests.

Hematologic Evaluation and Monitoring

Ability to monitor hematologic abnormalities of leukocytes, platelets and red cells over time including trending is essential in the management of canine and feline cancer patients. In clinic hematology analyzers for Point of Care (POC) testing are often preferred as information about hematologic parameters is needed in a timely fashion. Sending blood to reference laboratories may delay detection and evaluation of any changes important to address speedily. Awareness of the advantages and challenges of the precision of the measured parameters when using in clinic analyzers and the importance of having quality control measures in place is imperative. A recent study by Rishniw et al. VCP, 2016 illustrates this and underscores the importance of evaluating blood smears as part of routine hematology. Despite this POC hematology instruments on the market continuously increase in quality and usefulness of measured and reported parameters. The latest released advanced optical-based instruments using 2-dimensional laser light scattering technology all report both quantitative variables (cell counts) with information on leukocyte count and differential, platelet parameters including platelet count, size, shape and activation, red cell parameters including reticulocytes and qualitative distribution data in the format of histograms and color-coded dot plots. Unfortunately, most veterinarians do not take advantage of this valuable information about the patient's overall “hematologic state”.

“Novel” Platelet Parameters

The addition of several useful platelet parameters including plateletcrit (PCT, platelet percentage of blood volume), mean platelet volume (MPV, average volume of particles in blood counted as platelets), platelet volume distribution width (PDW, platelet size distribution), mean platelet component concentration (MPC, platelet granularity), mean platelet component distribution width (PCDW, variation in platelet shape), mean platelet dry mass (MPM, product of MPV and MPC) and presence of reticulated (immature) platelets may indicate increased platelet turnover and presence of platelet activation (increased MPV, MPM, MPC, PCDW and decreased MPC). This can help guide the clinician to underlying concurrent hemostatic disorders including disseminated intravascular coagulation (DIC), immune-mediated thrombocytopenia (IMT), and procoagulant conditions. Furthermore, the dot plots available on most instruments can qualitatively show presence of platelet aggregates as well as the platelet size distribution.

“Novel” Red Cell Parameters

Several useful red cell parameters in addition to the usual red cell indices MCV and MCHC are available. Most POC hematology instruments on the market today report reticulocyte counts as well as additional red cell parameters such as RDW (red cell distribution width).

Leukocyte Evaluation

Color-coded dot plots available on some instruments may help indicate abnormalities in leukocyte distribution and the presence of abnormal cells such as blasts.

On the Horizon

Recent research has placed increased emphasis on hemostatic and inflammatory evaluation of cancer patients including thromboelastography (TEG), TPA modified thromboelastography (TPA-TEG), evaluation of endogenous thrombin potential, C reactive protein (CRP) and cytokines, which in the future may be able to identify patients with concurrent inflammatory, thrombotic or fibrinolytic conditions. TEG guided transfusion is becoming increasingly available in specialty practice as an option to guide coagulation factor product administration in the bleeding cancer patient.

Automated bone marrow cell counting methods have been reported and may add more precision to bone marrow evaluation in the future. Furthermore, novel biomarkers including miRNA, proteome determinations, molecular expression patterns in hematologic malignancies, detection of circulating cancer cells and other liquid biopsy parameters all may become part of the routine management of canine and feline cancer patients in the future.

References

1.  Veterinary Cooperative Oncology Group. Common terminology criteria for adverse events (VCOG-CTCAE) following chemotherapy or biological antineoplastic therapy in dogs and cats v1.1. Vet Comp Oncol. 2016;14(4):417–446.

2.  Kristensen AT, Wiinberg B, et al. Evaluation of human recombinant tissue factor activated thromboelastography in 49 dogs with neoplasia. J Vet Intern Med. 2008;22:140–147.

3.  Rishniw M, Pion PD. Evaluation of performance of veterinary in-clinic hematology analyzers. Vet Clin Path. 2016;45:604–614.

4.  Schwartz D, Shanley L, et al. Platelet volume and plateletcrit in dogs with presumed primary immune-mediated thrombocytopenia. J Vet Intern Med. 2014;28(5):1575–1579.

5.  Fujino Y, Nakamura Y, et al. Development and evaluation of a novel in-clinic automated hematology analyzer, ProCyte Dx, for canine erythrocyte indices, leukogram, platelet counts and reticulocyte counts. J Vet Med Sci. 2013;75(11):1519–1524.