Endocrine response and outcome in 14 cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (17 Gy)

Abstract

OBJECTIVE To describe clinical outcomes in cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (SRS). ANIMALS 14 client-owned cats. PROCEDURES Medical records of cats with insulin resistance and acromegaly treated with SRS (17 Gy) between August 2013 and November 2019 at a single institution were reviewed. Kaplan-Meier analysis was used to evaluate overall survival time. RESULTS Acute adverse effects of SRS included somnolence (n = 2) and alopecia (1). Delayed adverse effects of SRS included unspecified neurologic complications (n = 1; 481 days), seizures (1; 1,541 days), and hypothyroidism (1; 64 days). Exogenous insulin requirements decreased in 10 of the 14 cats, with a median time to lowest insulin dose of 399 days (range, 42 to 879 days). Complete diabetic remission was achieved in 3 cats. The median overall survival time was 741 days (95% CI, 353 to 1,129 days). Six cats were still alive at the end of the study period, with a median follow-up time of 725 days. In 7 of the 8 cats that had died, death was presumptively attributed to acromegaly owing to continued insulin resistance, organ failure, or altered neurologic status. CLINICAL RELEVANCE The SRS protocol was well tolerated and associated with survival times similar to those reported previously. Most cats had decreased exogenous insulin requirements after SRS. Latency to an endocrine response was highly variable, emphasizing the need for careful ongoing diabetic monitoring of acromegalic cats after pituitary gland irradiation.

Dose- and Volume-Limiting Late Toxicity of FLASH Radiotherapy in Cats with Squamous Cell Carcinoma of the Nasal Planum and in Mini Pigs

“…Single fractions of up to 20 Gy are sometimes applied by veterinary radiation oncologists, but mostly in situations where only short-term outcome (palliation) is expected (C. Rohrer Bley's personal communication). However, in cats with expected long-term outcome, for example for pituitary tumors, 17 to 20 Gy were delivered in radiosurgically without obvious late toxicity ( 23 ). The herein observed osteoradionecrosis (ORN) points to realistic limitations of FLASH-radiotherapy, where a very high single dose of 30 Gy with a hotspot at 42 Gy exceeded the tolerance of the bone maxilla and the oral mucosa in cats, despite only grade 1 toxicity reported for skin.…”

Transsphenoidal hypophysectomy for the treatment of hypersomatotropism secondary to a pituitary somatotroph adenoma in a dog

“…for the treatment of hypersomatotropism and diabetes mellitus in cats, diabetic remission rates are not as high as those reported with surgical management, and little information is available regarding changes in serum IGF-1 concentration following treatment. 21,22 Serum IGF-1 concentration in our dog decreased rapidly to normal following surgery (396 ng/mL) and was persistently decreased at 11 weeks postoperatively (49 ng/mL), demonstrating the effectiveness of this procedure in achieving biochemical remission of acromegaly in this dog. As a result, surgical treatment by transsphenoidal hypophysectomy was effective in achieving remission of acromegaly in this dog and can be considered as a first-line treatment for dogs with pituitary adenoma-associated growth hormone excess.…”

“…There was improvement in glycemic control in both cases, and 1 dog achieved diabetic remission. While newer techniques, such as stereotactic radiation therapy, have been reported for the treatment of hypersomatotropism and diabetes mellitus in cats, diabetic remission rates are not as high as those reported with surgical management, and little information is available regarding changes in serum IGF‐1 concentration following treatment 21,22 . Serum IGF‐1 concentration in our dog decreased rapidly to normal following surgery (396 ng/mL) and was persistently decreased at 11 weeks postoperatively (49 ng/mL), demonstrating the effectiveness of this procedure in achieving biochemical remission of acromegaly in this dog.…”

Feline Comorbidities: Hypersomatotropism-induced diabetes in cats

“…Approximately 90% of patients experience a reduced tumour volume in these time periods. 55,56 Based on two published studies of stereotactic radiotherapy in cats, 57,58 the treatment is generally well tolerated, with mild radiationassociated side effects seen in up to 20% of cats. diabetic remission was reported to occur in 21-34% of cats, with a median time to lowest insulin dosage being 9-13 months post-treatment.…”