Cortisol-secreting adrenocortical tumour
Dogs with cortisol-secreting adrenocortical tumours can be treated with surgery, radiotherapy, and/or pharmacotherapy.
Surgery (adrenalectomy) is the preferred treatment because it eliminates the tumour and thus the cause of the cortisol excess with its associated side effects. There is no need for lifelong medication after surgery when the tumour is limited to one adrenal gland. In unilateral cases, because of the atrophy of the cortex of the non-cancerous contralateral adrenal gland, glucocorticoid substitution is needed temporarily for 6 to 8 weeks after surgery. When both adrenal glands need to be removed, the dog will need a lifelong supplementation of the hormones normally produced by the adrenal glands (glucocorticoids and mineralocorticoids).
The surgical removal of the adrenal gland can be performed via a classic “open abdomen” surgery or via laparoscopy (“closed abdomen”, i.e. surgery via small incisions and guided via an intra-abdominal camera). The advantages of the laparascopy include shorter hospital stays, and a faster recovery period. When tumours exceed 5 cm in diameter and/or when there is an invasion of a large blood vessel, the “open abdomen” technique is preferred.
Hypofractionated stereotactic volumetric-modulated radiotherapy was reported recently in 9 dogs with invasive cortisol-secreting adrenocortical tumours. The treatment resulted in a reduction of the tumour volume and a median survival time of 1030 days. These results are very encouraging; however, this modality is available in only few institutions in Europe (non-exhaustive list).
Among pharmacotherapy, ADH can be treated with trilostane or mitotane. Mitotane or trilostane therapy for ADH are used when surgery is not a good option for the dog or before surgery to stabilize the dog’s hypercortisolism.
In dogs with a cortisol-secreting adrenocortical tumour trilostane will only reduce the clinical signs and not affect the growth of the tumour and development of metastasis. The treatment is only palliative. More information about trilostane therapy is described in the section on ‘pituitary tumours’.
Another medical treatment option is mitotane. The advantage of mitotane is that it can destroy adrenocortical tumour cells and even metastases. Because the goal of mitotane therapy in cortisol-secreting adrenocortical tumours is not only to reduce cortisol production but also to destroy the neoplastic cells, a non-selective treatment protocol that affects the entire adrenal cortex should be considered. Each daily dose should be divided into three or four portions (every six-eight hours, with food). Because of this treatment the adrenal cortex no longer produces hormones, therefore these must be administered (substitution therapy).
Substitution therapy starts at the third day and consists of daily glucocorticoids, mineralocorticoids, and salt. After the initial course of mitotane has been administered, the glucocorticoid dose is reduced, but doubled for one or two days in the event of injury, severe physical stress, or anesthesia. To prevent recurrence, an adapted mitotane dose should be administered once weekly for at least 6 months, or even lifelong. Adverse effects of mitotane include anorexia, lethargy, weakness and diarrhea.
If they develop, the mitotane treatment must be temporarily discontinued, but the substitution therapy should always be maintained.
Aldosterone-secreting adrenocortical tumour
Aldosterone-secreting adrenocortical tumours can be surgically removed or treated via pharmacotherapy (with an aldosterone secretion blocker).
Hormonally silent adrenocortical tumour
For hormonally silent adrenocortical tumours, the most optimal treatment is surgical removal, when the adrenal mass diameter exceeds 2 cm. There is no pharmacotherapy available so far.