Assisting in the diagnosis of canine lymphoma
Lymphoma in dogs presents with a wide range of symptoms, however swollen lymph nodes (lymphadenopathy) is the strongest indication of the disease. Aspiration or biopsy of the affected lymph nodes remains the gold standard test for diagnosis of canine lymphoma and most practices will rely on fine needle aspiration (FNA) combined with cytological examination. However, FNA samples are often inconclusive or non-diagnostic. Additionally, the FNA approach is only applicable to cases presenting with peripheral lymphadenopathy. Since lymphoma can also affect the numerous internal lymph nodes illustrated in the following diagram, many cases cannot be accessed by FNA.
The cLBT provides a new and valuable tool in the diagnosis of canine lymphoma. It has been used to confirm the veterinarian’s diagnosis in cases when FNA results are inconclusive. It can also help in decisions for further costly investigations in cases of suspect non-peripheral lymphoma.
Cases studies which illustrate how cLBT has been used in cases of inconclusive or inaccurate FNA are illustrated below.
cLBT use in practice
- Can be used when you suspect lymphoma in patients showing classical symptoms such as generalised lymphadenopathy, PU/PD and lethargy.
- Used as an initial test for differentiating between benign lymphadenopathy and malignant lymphoma
- A useful reflex/add on test when hypercalcaemia is flagged up, establishing a more rapid diagnosis
- Monitoring treatment and recurrence of lymphoma
Monitoring Treatment and Recurrence of Lymphoma
It is well recognised that canine lymphoma usually responds well to first round chemotherapy. However, the disease invariably recurs and the second round treatment is considered to be less effective due to the development of resistance to the chemotherapy drugs, generally producing only short lived results.
For this reason, close monitoring of dogs undergoing chemotherapy is important.
The same is true for dogs that have entered remission and ceased treatment. It is believed that re-induction or rescue therapy may be more effective when recurrence is detected in its early stages.
Re-induction therapy is recommended at the first recurrence, and this usually involves reintroducing the original induction protocol. However, the likelihood of response and duration of a second remission period are approximately half of that achieved by the initial protocol. After re-induction, some dogs will experience long term remission, although there is currently no way of predetermining this response. When re-induction fails, rescue agents which were not included in the original protocol may be used. These include single agents such as lomustine, mitoxantrone or actinomycin D and also combination therapies such as MOPP (methclorethamine, vincristine, procarbazine and prednisolone). Response rates are reported to be in the range of 40 to 50%, but median survival times are only in the region of 2 months.
Monitoring for disease remission/recurrence is usually performed by palpation of peripheral lymph nodes. However, this can be a very subjective procedure which is only capable of detecting gross changes in peripheral lymph nodes. Biochemical methods which look for circulating biomarkers of the disease have the potential to provide greater objectivity whilst also detecting changes which precede peripheral lymphadenopathy.
A detailed study of 57 dogs from diagnosis to death1 has demonstrated that the cLBT is able to detect disease recurrence up to eight weeks in advance of the appearance of peripheral lymphadenopathy. By monitoring dogs with the cLBT every four to six weeks post treatment, veterinarians are now able to detect recurrence well before it was previously possible using palpation alone. This offers much more time to plan and implement re-induction or rescue therapies.
Accurate prognostic indicators for canine lymphoma have been lacking in veterinary oncology and veterinarians have relied on clinical stage, WHO sub stage, grade and immunophenotype as guidelines.
The cLBT data presented in our study indicate a potential prognostic value both at the point of diagnosis from the initial cLBT value and during treatment from the lowest cLBT score achieved by chemotherapy.
1I. Alexandrakis, R. Tuli, S. C. Ractliffe, S. W. Tappin, R. D. Foale, A. Roos and K. J. Slater. Utility of a multiple serum biomarker test to monitor remission status and relapse in dogs with lymphoma undergoing treatment with chemotherapy. Veterinary and Comparative Oncology. Article first published online: 15 OCT 2014 | DOI: 10.1111/vco.12123.