Hypofractionated radiation therapy for treatment of an adrenal mass in a ferret

Background: Ferret hyperadrenocorticism is the most common endocrine disease among domesticated ferrets. Current therapies include adrenalectomy and gonadotropin-releasing hormone analogs. Radiation therapy was used as an alternative noninvasive local therapy option. Case presentation: A 5-year-old male castrated ferret originally presented for pollakiuria. An abdominal ultrasound evaluation revealed an enlarged right adrenal gland with heterogenous parenchyma. Hypofractionated radiation therapy for treatment of the right adrenal mass was planned and performed using a small animal irradiator system. The prescribed radiation protocol was 30 Gray administered in 5 weekly fractions. The volume of the irradiated adrenal mass was serially quantified via the weekly cone beam CT. The adrenal mass volume decreased by 88% over the 10-month period. The ferret was euthanized 10 months postradiation therapy due to progressive co-morbidities, and the body was submitted for necropsy examination. No evidence of adrenal tissue or neoplastic tissue was found on histopathology of the irradiated right adrenal mass at the time of death. Evidence of systemic mycobacteriosis was discovered on necropsy. Conclusion and case relevance: Based on histopathologic evaluation, a complete response was achieved with hypofractionated radiation therapy of the right adrenal mass. Additional studies are needed to evaluate the safety and efficacy of this novel therapeutic approach.     

Myxosarcoma in the eye and brain in a dog

A male mixed breed dog of unknown age was presented with sudden onset of blindness and a slightly exophthalmic right eye. Ophthalmoscopically, a spherical, pinkish mass protruding from the region of the optic disc into the vitreous was seen in the right eye. Ultrasound and computer tomography demonstrated an extension of the mass into the right retrobulbar space, continuing intracranially to the optic chiasm. Cytologic findings, obtained by ultrasound-guided fine needle aspiration from the retrobulbar space, were consistent with myxosarcoma. On the basis of these findings of a well-delineated mass in the brain stem area, irradiation was planned as the therapy of choice. The dog was treated under general anesthesia using a proton beam at the Paul Scherrer Institute (PSI, Villigen, Switzerland). A curative protocol (56 Gy in 16 fractions over 4 weeks, 3.5 Gy/fraction) was used. Twenty-seven days post radiation therapy the dog was euthanized, as clinical symptoms progressed. Enlargement of the intracranial tumor was seen on a CT study repeated on the day of euthanasia. A gross pathologic and histologic examination were performed and confirmed the diagnosis of a myxosarcoma involving the eye, retrobulbar space of the right side, and the optic chiasm. Post-mortem examination failed to identify any abnormalities or metastases elsewhere in the body.     

Effects of radiotherapy on pituitary corticotroph macrotumors in dogs: a retrospective study of 12 cases

The efficacy of low doses of radiotherapy for the treatment of pituitary corticotroph macrotumors in dogs is evaluated retrospectively. Twelve dogs with pituitary-dependent hyperadrenocorticism and a large pituitary tumor treated with 36 Gy of radiation were included. Radiation was delivered in 12 fractions of 3 Gy over a 4- to 6-week period. Effects of radiation therapy on tumor size were assessed by computed tomography scans; a decrease was observed in 11 dogs (decrease > 50% in 6 dogs). Three dogs were reirradiated due to major tumor regrowth or a lack of tumor decrease (mean total dose: 22 Gy given in 3-Gy fractions over 3 or 4 weeks). The mean and median survival times following the initiation of radiotherapy were 22.6 months (688 days) and 17.7 months (539 days), respectively. These data are consistent with previous findings, based on high-dose radiation, showing that radiotherapy is a useful option for treating pituitary corticotroph macrotumors in dogs. Furthermore, computed tomography follow-up of the treated dogs demonstrates objectively the efficacy of radiotherapy against corticotroph tumors in dogs.     

Linear-Accelerator-Based Modified Radiosurgical Treatment of Pituitary Tumors in Cats: 11 Cases (1997–2008)

Objective: Determine the efficacy and safety of a linear-accelerator-based single fraction radiosurgical approach to the treatment of pituitary tumors in cats.
Design: Retrospective study.
Animals: Eleven client-owned cats referred for treatment of pituitary tumors causing neurological signs, or poorly controlled diabetes mellitus (DM) secondary either to acromegaly or pituitary-dependent hyperadrenocortism.
Procedures: Cats underwent magnetic resonance imaging (MRI) of the brain to manually plan radiation therapy. After MRI, modified radiosurgery was performed by delivering a single large dose (15 or 20 Gy) of radiation while arcing a linear-accelerator-generated radiation beam around the cat's head with the pituitary mass at the center of the beam. Eight cats were treated once, 2 cats were treated twice, and 1 cat received 3 treatments. Treated cats were evaluated for improvement in endocrine function or resolution of neurological disease by review of medical records or contact with referring veterinarians and owners.
Results: Improvement in clinical signs occurred in 7/11 (63.6%) of treated cats. Five of 9 cats with poorly regulated DM had improved insulin responses, and 2/2 cats with neurological signs had clinical improvement. There were no confirmed acute or late adverse radiation effects. The overall median survival was 25 months (range, 1–60), and 3 cats were still alive.
Conclusions and Clinical Importance: Single fraction modified radiosurgery is a safe and effective approach to the treatment of pituitary tumors in cats.     

Radiation therapy in two cats with pituitary tumors

Two cats with large pituitary neoplasms (adenoma and adenocarcinoma) were treated with fractionated radiation therapy. Total doses of 40 Gy, respectively 36 Gy, were applied in 10 fractions of 4 Gy, and 3.6 Gy respectively. Side effects were minimal and transient. Anesthesia was well tolerated. Improvement of clinical signs could be observed during radiation therapy in both cats. One cat had a complete, the other a partial tumor response. One cat (suspicion of adenoma) was euthanized 1 3/4 years after therapy due to unrelated disease. No tumor was found on histopathology, however a small focal necrosis of brain tissue in the irradiated field was observed. The second animal with a pituitary adenocarcinoma was euthanized because of tumor recurrence 1 1/2 years after therapy. Radiation therapy was effective, despite the low total doses of radiation applied.     

Coarse fractionated radiation therapy for pituitary tumours in cats: a retrospective study of 12 cases

This retrospective study describes the clinical progression of 12 cats with pituitary tumours treated with a coarse fractionated radiation protocol delivering a total dose of 37 Gy in five once weekly fractions. A pituitary macrotumour was identified in all 12 cats: 4 with neurological signs only and 8 with insulin‐resistant diabetes mellitus secondary to acromegaly. One of the cats with central neurological signs died before completing the radiotherapy course; the remaining three had partial or complete remissions of their central neurological signs. Of the cats with unstable diabetes mellitus, five no longer required insulin therapy, one required less insulin and two became stable. The overall median survival time was 72.6 weeks; four cats died from related causes, two from unrelated problems and six remain alive. Radiation therapy is confirmed as an effective treatment for feline pituitary tumours, giving prolonged survival and control of both paraneoplastic and mass effect signs.     

Outcomes of pituitary tumor irradiation in cats

BACKGROUND: Information on tumor control and normal tissue effects of radiotherapy to treat pituitary tumors in cats is limited. HYPOTHESIS: Radiation therapy is effective in controlling the clinical signs associated with pituitary tumors in cats, with a low incidence of adverse effects. ANIMALS: Eight cats were irradiated at Colorado State University between 1991 and 2002 for spontaneous pituitary tumors. METHODS: A retrospective review of records was made to assess tumor control and incidence of radiation-induced adverse effects. RESULTS: Pituitary carcinoma was diagnosed in 2 cats and pituitary adenoma in 6 cats. Total radiation dosage ranged from 4,500 to 5,400 cGy administered Monday through Friday in 270 or 300 cGy fractions. Acute effects were limited to epilation and mild otitis externa. Focal brain necrosis adjacent to regrowth of a pituitary carcinoma and a second tumor in the radiation field were reported as possible late effects. Median survival, regardless of cause of death of the 8 cats, was 17.4 months (range, 8.4 to 63.1 months). Median survival could not be determined if cats were censored for non-tumor-related causes of death. Six cats were alive at 1 year, and 3 cats were alive at 2 years after treatment. Tumor recurrence was seen in 1 cat with a pituitary carcinoma. Neurologic signs improved within 2 months in all 5 cats that presented with abnormal neurologic signs. Clinical signs caused by a concurrent endocrine disorder began to improve within 1-5 months in the 7 cats with hyperadrenocorticism or acromegaly. CONCLUSIONS AND CLINICAL RELEVANCE: Radiation therapy is an effective primary treatment modality for cats presenting with neurologic signs associated with a pituitary mass and can improve clinical signs associated with concurrent hyperadrenocorticism or acromegaly in cats with no neurologic abnormalities.     

Treatment of an osteoblastic osteosarcoma in an aged gelding

A 27‐year‐old Thoroughbred gelding was examined for a right nasal mass visible inside the right nares. Airflow through the right nostril was absent. Endoscopy and radiography revealed the mass to occupy the entire right nasal passage. Nasal biopsies were inconclusive, so en bloc resection was performed. A diagnosis of an incompletely resected osteoblastic osteosarcoma was made. Endoscopic biopsies performed 4 weeks post surgery revealed osteosarcoma cells present in the caudal right nasal cavity. Metastatic disease was not present in mandibular lymph node aspirates or on thoracic radiographs. The right nasal passage was irradiated with 12 treatments over the course of 4 weeks. Comfort and quality of life were excellent during treatment and no adverse side effects were noted. Endoscopy and follow‐up biopsies at 1, 2, 4, 12 and 14 months post radiation therapy have not found any evidence of regrowth of the osteosarcoma.     

Surgical and Localized Radiation Therapy for an Intranasal Adenocarcinoma in a Rabbit

An 8-year-old spayed female Netherland Dwarf rabbit presented with a two-month history of dyspnea and snoring. A computed tomography (CT) scan of the head revealed mass lesions in the right nasal cavity. Surgical exenteration of the lesions was performed, and the histopathological diagnosis was an intranasal adenocarcinoma. On the basis of this diagnosis, radiotherapy was planned and consisted of eight fractions of 6 Gy administered once a week. After the completion of radiation therapy, the soft tissue density in the right nasal cavity, as detected by CT, significantly decreased. The prognosis has remained good for over 3 years after treatment. This paper is the first to describe the clinical and pathological features of an intranasal tumor in a rabbit.     

LATE COMPLICATIONS OF PELVIC IRRADIATION IN 16 DOGS

When external beam radiation therapy is administered to the pelvis, normal tissues irradiated may include the colon, small intestine, urethra, bladder, bone, and spinal cord. The objectives of this retrospective study were to determine the incidence and severity of late radiation effects following pelvic irradiation in dogs and to identify factors that increase the risk of these effects. Medical records of all dogs treated with curative intent external beam radiation therapy to the pelvic region between 1993 and 1999 were reviewed. Patients with follow-up longer than 9 months or any patient that developed late complications earlier than 9 months were evaluated. Sixteen dogs met criteria for inclusion in this study. All dogs were treated with a 6-MV linear accelerator with bilaterally opposed beams. Diseases treated included transitional cell carcinoma of the bladder, transitional cell carcinoma of the prostate, and anal sac apocrine gland adenocarcinoma. Four dose/fractionation schemes were used: 49.5 Gy in 3.3 Gy fractions, 54 Gy in 3.0 Gy fractions, 54 Gy in 2.7 Gy fractions, and 18 Gy intraoperative radiation therapy followed by 43 Gy external beam radiation therapy in 2.9 Gy fractions. Implantable chemotherapy in the form of an OPLA-Pt sponge was used in six dogs as a radiation potentiator. Colitis was the major late effect following pelvic irradiation, occurring in nine dogs (56%). Colitis was characterized as mild in three dogs, moderate in one dog, and severe in five dogs. Three of the dogs with severe effects suffered gastrointestinal perforation. All dogs with severe late effects received 3 or 3.3 Gy per fraction, and 80% received radiation potentiators. In the seven dogs that received 2.7 Gy or 2.9 Gy per fraction, late effects were classified as none (n = 5), mild colitis (n = 1), and moderate colitis (n = 1). Radiation therapy can be administered to the pelvic region with a minimal risk of late effects to the colon by giving smaller doses per fraction and avoiding systemic radiation potentiators.     

Coarse Fractionated Radiation Therapy for Pituitary Tumours in Cats: A Retrospective Study of 10 Cases

Introduction:  Pituitary tumours are uncommon in cats. Signs may be due to either an expansile mass or paraneoplastic effects (acromegaly and/or unstable diabetes mellitus). There are a few small case series providing evidence of efficacy for radiotherapy of pituitary tumours in cats. This retrospective study describes the outcome of ten cats with pituitary tumours treated with course‐fractionated radiation.
Methods:  The medical records of cats with MRI‐confirmed pituitary tumours that underwent radiotherapy were reviewed. A standard coarse‐fractioned radiation protocol was used; 37 Gy in 5 once‐weekly fractions using two parallel‐opposed 4MeV X‐ray beams. Survival times were calculated from date of first radiation dose.
Results:  Ten cats with pituitary tumours underwent radiotherapy. 5 cats had CNS signs and 5 had evidence of growth hormone excess (1 cat also showed CNS signs). 2 cats with pre‐existing moderate to severe CNS signs died of unknown causes before completing the radiation course. Of the remaining 4 with CNS signs, 3 had complete resolution of signs and the fourth showed partial improvement. Of the 5 cats with unstable diabetes, 2 no longer required insulin and 3 became stable at a lowered dose. The median survival time was 77.6 weeks. 6 cats died: 2 without completing the radiation course, 2 from unrelated causes (CRF, VAFS) and 2 from relapse and/or progression of CNS signs. 4 cats remain alive (range 34–191 weeks).
Conclusions:  Radiation therapy is confirmed as an effective treatment for pituitary tumours in cats giving extended survival and control of both direct mass effect and paraneoplastic signs.     

Radiation Therapy of Canine Brain Masses

This article evaluates the responses of 14 dogs with brain masses using orthovoltage irradiation for definitive treatment. Dogs were anesthetized for computed tomography (CT) examination, formation of head immobilization and positioning devices, radiation treatment simulation, and treatments. Total doses of 39 Gy (9 dogs) or 45 Gy (5 dogs) to the tumor were administered over 25 to 41 days. Two or three portals (parallel opposed lateral with or without a dorsal field) were used. Treatment volumes included the tumor and peritumoral edema, as determined by CT scan, and a 1-cm margin. Histopathologic diagnoses were available in 9 of 14 dogs. There were 4 meningiomas, 1 lymphosarcoma, 1 pituitary adenoma, 1 metastatic anaplastic carcinoma, 1 anaplastic oligodendroglioma and 1 dog with granuloma-tous meningoencephalitis. At the end of radiation therapy, 10 dogs could be evaluated for progression of clinical signs: 3 dogs deteriorated or failed to improve, and 7 dogs improved. At the time of analysis, all dogs were dead. Mean and median survival times, measured from the beginning of radiation, were 345 and 489 days, respectively. This was compared with mean survival times of 30 to 81 days reported in the literature for dogs with brain tumors that did not receive treatment. The median survival time of 9 dogs treated with 39 Gy was 153 days, versus 519 days for 5 dogs that received 45 Gy. It appears that radiation therapy prolongs survival times for dogs with brain masses. Although megavoltage therapy would be optimal, orthovoltage radiation can be applied in total doses of 45 Gy in 3.75 Gy fractions over 28 days without adverse effects. Histopathologic evidence of multifocal demyelination and astrocytosis may be found. (Journal of Veterinary Internal Medicine 1993; 7:216–219. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Successful treatment of feline hyperadrenocorticism with pituitary macroadenoma using radiation therapy: a case study

A 10-year-old castrated male cat showing behavioral (irritation, prowling, and tumbling) and cutaneous abnormalities such as dermal fragility was diagnosed as hyperadrenocorticism with pituitary macroadenoma, concurrent with insulin dependent diabetes mellitus. Pituitary enlargement (18.0 mm) was observed during magnetic resonance imaging. High endogenous adrenocorticotropic hormone levels (>2,500 pg/ml) were also observed. Although trilostane treatment (5–10 mg/head, daily) was commenced, the clinical signs did not disappear. Insulin and trilostane treatment were discontinued on day 86 after first day of radiation therapy (4 Gy/12 fractions). After radiation therapy, a decreased pituitary tumor size (10.7 mm) was observed on day 301; neurological and dermatological signs exhibited remission. Radiation therapy is the treatment of choice for feline hyperadrenocorticism with pituitary macroadenoma with neurological signs.     

Effects of mitotane therapy in dogs with pituitary dependent Cushing syndrome on the adrenal gland size--an ultrasonographic study]

The effect of mitotane therapy on adrenal gland size was evaluated in 13 dogs with pituitary dependent hyperadrenocorticism. Ultrasonographic measurements were obtained before and during mitotane therapy. During therapy both adrenal glands were shorter and thinner (median during therapy: left adrenal gland 19.4 mm long, 5.4 mm thick, right adrenal gland 18.1 mm long, 6.1 mm thick) than before mitotane therapy (median before therapy: left adrenal gland 23.6 mm long, 8.3 mm thick, right adrenal gland 21.6 mm long, 8.1 mm thick). Statistical evaluation showed a significant reduction in size. But ultrasonographic measurement of adrenal gland size is not useful in the evaluation of adrenal reserve during mitotane therapy. Inadequate adrenal reserve was not identified and adrenal size measurement by ultrasonography was not helpful to differentiate adequate and inadequate control of adrenal cortisol secretion during mitotane therapy.     

RADIATION THERAPY COMMUNICATION—REIRRADIATION OF A NASAL TUMOR IN A BRACHYCEPHALIC DOG USING INTENSITY MODULATED RADIATION THERAPY

A 5‐year‐old spayed female Shih Tzu was referred for evaluation of a nasal transitional carcinoma. A total lifetime dose of 117 Gy was delivered to the intranasal mass in three courses over nearly 2 years using fractionated intensity modulated radiation therapy (IMRT) to spare normal tissues. Clinically significant late normal tissue side effects were limited to bilaterally diminished tear production. The patient died of metastatic disease progression 694 days after completion of radiation therapy course 1. This case demonstrates that retreatment with radiation therapy to high lifetime doses for recurrent local disease may be well tolerated with IMRT.     

Successful use of prednisolone and radiation therapy in a dog with intracranial histiocytic sarcoma

The ideal treatment for intracranial histiocytic sarcoma (HS) remains unclear. Herein, we report a case of intracranial HS that was successfully treated using prednisolone and radiation therapy. The patient was a 9-year-old spayed female Pembroke Welsh Corgi that presented with epileptic seizures. Magnetic resonance imaging revealed a contrast-enhancing mass adjacent to the right piriform lobe. Prednisolone administration (1 mg/kg/day) decreased the lesion size. Additional palliative radiation therapy (total dose, 37 Gy) resulted in complete disappearance of the lesion. However, on day 164, the dog’s neurological signs deteriorated, and she was euthanized. Necropsy revealed an intracranial metastasis of HS via the cerebrospinal fluid without any extracranial metastasis. Nonetheless, combined prednisolone and radiation therapy might be effective in treating intracranial HS.     

Chronic ocular lesions associated with bi-directional microbeam radiation therapy in an experimental rat study for therapy of C6 and F98 gliomas

Objectives  To describe the chronic ocular lesions associated with microbeam radiation therapy (MRT) in an experimental rat study.
Procedures  MRT was administered bi-directionally with a skin entry dose of 350 Gy. During laterally directed irradiation, the beam entered the head on the right with the center of the beam array 3 mm posterior to the center of the right eye. During irradiation in anterior-posterior direction, the right eye was almost completely in the path of the beam array. Twelve months after MRT ophthalmic examinations were completed on 37 treated (MRT+) and 16 control (MRT–) rats. Electroretinography (ERG) was completed in two MRT+ and one MRT– rat. Histopathology was performed on eyes of 16 MRT+ and 9 MRT– rats, and retinal and choroidal thicknesses were measured.
Results  Biomicroscopic and indirect ophthalmoscopic examinations revealed fundus pallor and retinal vascular attenuation in 33 of 37 right and 2 of 37 left eyes of MRT+ rats. Cataracts were present in the right eyes of 12 of 37 MRT+ rats. ERG amplitudes were reduced in the eyes of MRT+ rats. Light microscopy revealed retinal lesions ranging in severity with loss of outer to inner retinal cell layers, in 16 of 16 right and of 8 of 16 left eyes MRT+ rats. The mean right retinal thickness of MRT+ rats was reduced.
Conclusions  Eyes within the field treated with MRT at a dose of 350 Gy develop retinal degeneration and occasionally, cataract.     

Retrospective study of canine nasal tumor treated with hypofractionated radiotherapy

The object of this study was to evaluate hypofractionated multiportal field and two-portion (rostral and caudal portions divided by the eyelid) radiation therapy for canine nasal tumors. Sixty-three dogs underwent multiportal hypofractionated radiation therapy. The radiation field was divided into rostral and caudal portions by the eyelid. Treatments were performed four times for 57 dogs. The median irradiation dose/fraction was 8 Gy (range, 5-10 Gy); the median total dose was 32 Gy (10-40 Gy). Improvement of clinical symptoms was achieved in 53 (84.1%) of 63 cases. Median survival time was 197 days (range, 2-1,080 days). Median survival times with and without destruction of the cribriform plate before radiotherapy were 163 and 219 days, respectively. There was no significant difference between them. No other factors were related to survival according to a univariate analysis. All radiation side effects, except one, were grade I according to the VRTOG classification. It was not necessary to treat any dogs for skin side effects. One dog (1.6%) developed an oronasal fistula 1 year after completion of radiation therapy. This radiation protocol may be useful in reducing radiation side effects in dogs with cribriform plate destruction.     

Use of strontium-90 plesiotherapy for the treatment of a lingual plasmacytoma in a dog

A 12-year-old, 25 kg, intact male St Bernard crossbreed was presented for treatment of a 538 mm ulcerated tumour on the dorsal tongue. Fine-needle aspiration cytology revealed a plasmacytoma. The dog staged negative for evidence of local metastatic or systemic disease. Histopathology confirmed the diagnosis. Treatment with one 150 Gy dose of radiation delivered with strontium-90 plesiotherapy was performed. Side effects were not noted and there was no visible evidence of tumour remaining at 2 months and 1 year after therapy.