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WSV18-0154
ONCOLOGY
DIAGNOSIS AND TREATMENT OF ENDOCRINE NEOPLASIA IN DOGS AND CATS
S. Ryan1, C. Cannon1
1The University of Melbourne, UVet Hospital, Werribee, Australia
IAGNOSIS AND TREATMENT OF ENDOCRINE NEOPLASIA IN DOGS AND CATS
Claire Cannon BVSc (hons) DACVIM (Oncology) MANZCVS
Stewart Ryan BVSc (hons) MS DACVS MANZCVS University of Melbourne U-Vet Animal Hospital claire.cannon@unimelb.edu.au stewart.ryan@unimelb.edu.au
Learning objective: Develop an algorithm for diagnosis and staging of thyroid tumours in dogs and adrenal tumours in dogs and cats. Understand rational application of different treatment modalities in different situations.
1. Thyroid tumours:
Cats with thyroid tumours typically present for clinical signs of hyperthyroidism, dogs for a palpable mass. Although dogs with thyroid tumours are rarely hyperthyroid, elevated T4 in a dog is almost certainly due to a thyroid tumour (rather than hyperplasia). Thyroid carcinoma represents the least common cause of
feline hyperthyroidism. Once a thyroid tumour in a dog
is palpable, it is almost certainly malignant. Because
size and mobility is an important prognostic factor in canine thyroid tumours, early detection via routine
neck palpation as part of regular physical examination should be emphasised in dogs. Carcinoma should be considered in hyperthyroid cats with extremely elevated T4, very large or fixed goitre. Screening for metastasis
is warranted in cats with suspected thyroid carcinoma, and treatment with surgery or I 131 may be more effective than medical management, however the true best approach is not defined.
In evaluation of a dog with a suspected thyroid tumour, our general approach is as follows:
1. Confirm cervical mass is of thyroid origin and assess resectability - thyroid origin can be confirmed with imaging (ultrasound or CT scan) and cytology, though cytology is not specific for malignancy (often thyroid carcinomas have few cytologic criteria of malignancy). Mobility is best assessed under heavy sedation or general anesthesia. If a thyroid tumour appears to be relatively fixed/immobile, contrast
CT scan should be avoided if I 131 treatment is a
43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS
25-28 September, 2018 | Singapore
excision. This can be acheived by open ventral midline laparaotomy approach or via a retroperitoneal approach. For smaller adrenal masses without caval invasion, laparoscopic adrenalectomy is possible. Tumour invasion into the phrenicoabdominal vein and caudal vena cava require venotomy to remove the tumour emboli. In
the case of phaeochromocytoma, pre-operative use
of phenoxybenzamine decreases the perioperative mortality rate. After the perioperative period, outcomes for both adrenal carcinomas and phaeochromocytomas can be very good in dogs. Vascular invasion, emergency surgery for haemorrhage, and large tumour size increases the perioperative risk but do not necessarily impact on long term outcome.
In non-resectable adrenal tumours, stereotactic radiation therapy has been recently reported with good outcomes (several year survival time). Adjuvant therapy following surgery has not been established in companion
animals. For adrenal dependent hyperadrenocorticism, if surgery is not a good option medical therapy can be attempted. MItotane can be used as a cytotoxic agent (higher doses than required for pituitary dependent hyperadrenocorticism are typically required, and approaches to ablate the adrenal tissue are described), or trilostane to control clinical signs can also be considered. Other chemotherapy agents have not been evaluated in companion animals with adrenal gland tumours.








































































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