8 Feb 2016
Iain Grant
Job Title
Figure 1. Percentage of samples from 57 dogs showing remission status (expressed as partial remission; PR) or progressive disease (PD) status as assessed by the veterinarian at the time of sampling to the cLBT score at the same time point for each dog. Below each time period is the number of samples assessed at that point. Error bars illustrate 95 per cent confidence intervals.
Lymphoma continues to be one of the most common malignancies affecting dogs. Ongoing research is critical to improving treatment outcomes, according to the author, who looked into the role a canine lymphoma blood test (cLBT) plays in the detection and monitoring of lymphoma and how UK vets can benefit from using this test in their daily practice.
Cases of canine lymphoma are pretty regular in UK-based small animal veterinary practice. As for the most common haematopoietic tumour, around 25 new cases per 100,000 dogs are diagnosed each year.
However, the annual incidence rate may be much higher when considering cases where diagnosis is unconfirmed.
The arrival of cLBT as a tool for lymphoma diagnosis and remission monitoring will undoubtedly help vets move forward in terms of providing clients with prognostic information for their pets and planning treatment.
The test is a simple, quick and effective way to test blood proteins related to the presence of lymphoma, allowing veterinary professionals to closely monitor a dog in remission and act quickly to set in motion a suitable response in the face of impending relapse.
As a relatively new diagnostic and prognostic tool (Panel 1), cLBT shows great promise and provides invaluable information for veterinary teams and owners.
One of the areas the test is proving useful in is in lymphoma remission monitoring. Canine lymphoma can respond very well to first round chemotherapy, but the disease invariably recurs and reinduction therapy may be less effective due to the development of resistance to chemotherapy drugs.
It may be the case that reinduction or rescue therapies harness greater results when recurrence is detected in its earliest stages and the test enables you to identify this and act quickly and decisively.
The development of cLBT marks progress for patient and owner care, allowing an owner to see the full picture when it comes to his or her pet’s response to treatment and making informed decisions during what can be an extremely stressful time.
The test is the work of veterinary oncologists, veterinary practices and mathematicians in the UK, the US and the Netherlands. The development was carried out in two phases:
Two biomarkers were discovered using mass spectrometry. These were acute phase proteins (APPs): C-reactive protein (C-RP) and haptoglobin (HAPT). C-RP levels increase in conditions such as canine lymphoma and C-RP testing is now routine in the diagnostic work-up of
non-Hodgkin’s lymphoma in humans.
C-RP alone lacks specificity in the diagnosis of lymphoma in dogs. Therefore, by adopting a multi-variant analytical approach employing both C-RP and HAPT values and using other clinical information, such as the presence of lymphadenopathy, cLBT was developed. This test overcomes the limitations found by measuring single APPs.
Carrying out cLBT is straightforward. Using 1ml of serum collected from the patient it is possible to measure the levels of C-RP and HAPT. To generate a test result, these readings are analysed with an algorithm to assist in the diagnosis of lymphoma. It can be used as part of blood work during an initial appointment.
The benefits of cLBT as a diagnostic tool are no sedation is required and results can be available within 24 hours of a sample receipt. When patients showing common lymphoma symptoms, such as generalised lymphadenopathy or when polyuria/polydipsia and lethargy are presented, cLBT enables the veterinarian to consider a diagnosis of malignant lymphoma early on in the diagnostic process.
Lymphoma is generally considered to be one of the most common causes of hypercalcaemia in dogs. However, the associated disease may be in an occult location and cannot be detected peripherally. Therefore, cLBT offers a diagnostic test that can significantly increase the index of suspicion for the presence of lymphoma in a dog’s body.
This makes it a very valuable add-on test to complement routine biochemistry, aiding in a more targeted investigation and rapid diagnosis of neoplasia as the underlying cause for the hypercalcaemia. Another benefit of using the test is it is less invasive.
Traditionally, monitoring for remission and subsequent relapse has been performed by palpation of peripheral lymph nodes with respect to the most common multi-centric form of the disease. However, such assessment can be imprecise and is only capable of detecting gross changes in size and texture of the nodes.
Biochemical methods based on detection of circulating biomarkers of lymphoma have the potential to provide greater objectivity while also detecting changes preceding palpable peripheral lymphadenopathy.
According to a study of 57 dogs undergoing lymphoma chemotherapy during and after treatment (Alexandrakis et al, 2014), cLBT was able to predict disease recurrence up to eight weeks in advance of the appearance of peripheral lymphadenopathy, giving veterinary teams more time to plan and implement reinduction or rescue therapies (Figure 1).
The precise impact of potential early reinduction treatment on overall survival times in canine lymphoma patients has yet to be fully evaluated, but represents a considerable step forward in the precision of patient monitoring.
A test score for the dog, ranging from zero to five, is generated using cLBT. Statistical modelling from the study demonstrates the value of the score for predicting the patient’s disease status either diagnostically or while receiving chemotherapy treatment:
For each sequential sample, an updated graphic showing the assessment of the disease status of the dog, along with the historical results, is provided (Figure 2).
Although relatively new, cLBT is already being relied on by veterinary oncologists as well as the wider profession.
To demonstrate the features of the test, the author refers to the case of Ernie, a five-year, seven-month-old male neutered Jack Russell terrier, who was examined at a primary vet practice with a history of rectal prolapse.
After referral and a full clinical work-up, eosinophilic colitis was identified histologically on mucosal biopsies from the rectum.
Unexpectedly, high grade T-cell lymphoma was also diagnosed based on fine needle aspiration biopsy and flow cytometry carried out on a sample collected from a single enlarged abdominal lymph node. This was identified through a routine ultrasound examination of the abdomen during the patient’s diagnostic evaluation.
Ernie was assigned stage one status for his disease. Despite recommendations, his owner declined surgical removal of the lymph node for definitive histological diagnosis.
It was decided to treat Ernie in practice with a discontinuous, multi-drug chemotherapy protocol delivering two cycles of treatment over nine weeks.
Due to the occult location of disease it was decided to use cLBT in this case for several reasons:
A rising score would, however, indicate the need for repeat abdominal ultrasounds to examine for disease relapse, although it was acknowledged the score could climb in advance of measurable lymphadenopathy.
The baseline score was 2.03 and was, therefore, suspicious for the presence of lymphoma, in keeping with the clinicopathological assessment of the patient.
After four weeks of chemotherapy treatment, cLBT was 0.19 (typical for a patient in complete remission). As this was the first case in which we had used the test, an abdominal ultrasound was repeated to corroborate the result and this indicated resolution of the previously documented lymphadenopathy.
On completion of therapy (during week nine), the score was 1.15 and a final abdominal ultrasound scan agreed with these findings. Eight and 16 weeks following completion of therapy (the last test taken), the score remained level at 1.15.
Ernie remained clinically well and the owner and veterinarian were happy with the ease and convenience of patient monitoring using this diagnostic test.
Although the initial score was in the suspicious range, the burden of disease was low – only one node affected – and raises the question of how the stage of disease may affect the cLBT result.
The dramatic drop in cLBT in response to therapy, confirmed ultrasonographically as a complete remission, would validate the usefulness of the test in this case to indicate a treatment response. The results of the follow-up monitoring tests are in the mid-range for patients free of disease and in ongoing remission.
A second case study highlighting the benefits of introducing cLBT into daily practice refers to an 11-year-old female spayed springer spaniel diagnosed with lymphoma in February 2013.
It was presented to Andre Raff, at Anchorage Vet Hospital in Acle, and was in remission having received chemotherapy with the cyclophosphamide, doxorubicin, vincristine and prednisolone protocol.
cLBT was carried out every four to six weeks to monitor for relapse after completing the chemotherapy protocol. In the first few months following chemotherapy, its cLBT score remained at 1.40 (indicating she was in remission).
However, after a score of 2.47 was returned in July 2014 (indicating a suspicion for the re-emergence of lymphoma), it was referred for rescue chemotherapy.
Although Anchorage Vet Hospital offers chemotherapy in house, in rescue situations it often prefers to get an “expert opinion”.
According to Mr Raff, the use of cLBT for remission monitoring allowed his team to accurately follow his patient’s disease and ensure continuity of care.
After completing the patient’s second chemotherapy protocol, repeat monitoring using cLBT has shown it has continued to stay in remission, as its final test confirmed.
The results from a separate retrospective study for remission monitoring over a period of four years (2008-2012;
http://bit.ly/1nlCD3B). The results show:
As previously stated, regularly monitoring patients using cLBT facilitates earlier intervention in chemotherapy management. If a patient is in an oncologist’s care, but monitored in general practice, this could lead to an early re-referral of dogs and timelier planning of appropriate treatment strategies.
Where possible, it is preferable to obtain a pretreatment baseline sample. Thereafter, it is recommended the dog is tested at four to six-week intervals to ensure accurate assessment of remission status and early detection of lymphoma recurrence (Figure 3).
With such impressive strides already being made, there is more research to be done and many more case studies to be documented.
The author expects to see cLBT play a greater role in diagnosis and remission monitoring as more evidence of its potential comes to light.
