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.     

RADIATION INDUCED VERTEBRAL OSTEOSARCOMA FOLLOWING TREATMENT OF AN INTRADURAL EXTRAMEDULLARY SPINAL CORD TUMOR IN A DOG

A 2-year-old neutered female Rottweiler diagnosed with an intradural extramedullary spinal cord tumor at T12-T13 was successfully treated with cytoreductive surgery followed by Cobalt 60 teletherapy. The dog was euthanised 5-and-a-half years later following diagnosis of an osteosarcoma involving the L1 and L2 vertebrae. Evidence of the initial tumor was not present at necropsy. The vertebral neoplasm fulfilled all of the accepted criteria for a radiation induced tumor. It was concluded that adjunctive irradiation should be considered for treatment of intradural extramedullary tumors of young dogs when total surgical resection is not possible. Although tumor induction is a rare late effect of radiation therapy, the risk of this occurrence should be considered when irradiating young animals. Radiation induced tumors in dogs have been associated with coarse fractionation schemes, or when large intraoperative doses have been administered. A lower dose per fraction, e.g., 3 Gy/fraction or less, is advisable when irradiating young dogs or any dog in which the life expectancy is 3-5 or more years after irradiation.     

A RETROSPECTIVE STUDY OF 27 DOGS WITH INTRANASAL NEOPLASMS TREATED WITH COBALT RADIATION

Twenty-seven dogs with sinonasal neoplasms were treated with cobalt radiation. Cytoreductive surgery was performed in six of the patients prior to initiation of irradiation. Dogs received from 4,180 to 5,400 cGy on a Monday/Wednesday/Friday schedule given in 10 to 12 fractions over a four week period. All dogs had a computed tomography (CT) based, computer generated radiation treatment plan. Survival time ranged from 2.5 to 46.0 months with a mean and median of 20.7 ± 3.3 and 12.8 months, respectively. The one- and two-year survival rates were 59% and 22%. Survival time compares favorably to those reported previously for dogs treated with cytoreductive surgery and orthovoltage x-rays. Survival time is longer than that reported previously using megavoltage radiation alone or in conjunction with surgery. It is likely that the improved survival reported herein is, at least in part, related to the use of computed tomography for tumor localization and computer generation of the treatment plan. No prognostic variables were identified in the present study. Survival time was not significantly different between dogs with carcinoma versus sarcoma. There was no significant difference between patients that had undergone cytoreductive surgery prior to radiotherapy, and those patients treated with radiotherapy alone.     

Surgical excision of a feline orbital lacrimal gland adenocarcinoma with adjunctive cryotherapy and carboplatin‐impregnated bead implantation

The purpose of this report was to discuss the diagnosis, treatment, and outcome of a cat with an orbital lacrimal gland adenocarcinoma. A 14.5‐year‐old spayed female domestic shorthair cat was evaluated for a firm swelling at the left dorsotemporal orbital rim. The orbital mass was excised with preservation of the globe, and adjunctive cryotherapy was performed. A definitive diagnosis of lacrimal gland adenocarcinoma was obtained after histopathologic evaluation and histochemical staining with periodic acid–Schiff and mucicarmine. Thirteen months postoperatively, tumor regrowth occurred with a much larger osteolytic lesion, and a second surgery was performed consisting of tumor excision with implantation of carboplatin‐impregnated calcium sulfate hemihydrate beads. The cat has remained free of recurrence 11 months after the second surgery (26 months after initial diagnosis and surgery). A feline orbital lacrimal gland adenocarcinoma was successfully managed utilizing globe‐preserving surgical excision with adjunctive cryotherapy and subsequent carboplatin‐impregnated bead implantation. Orbital lacrimal gland adenocarcinoma in cats may not be as aggressive as other forms of periocular, head, and neck adenocarcinomas.     

0–7–21 Radiation Therapy for the Treatment of Canine Oral Melanoma

Eighteen dogs with malignant melanoma of the oral cavity were treated with high-dose per fraction (0–7–21) radiation therapy. Eight hundred cGy was administered on days 0, 7, and 21 for a total dose of 2,400 cGy in 3 weeks. Of 17 dogs evaluated, 9 (53%) had a complete remission and 5 (30%) achieved a partial remission with an overall response rate of 83%. Local failure occurred in 2 of the 9 dogs where a complete response was initially observed. One dog died of intercurrent disease, and one died of metastatic disease without evidence of local recurrence. Five dogs are alive and free of disease 9 to nineteen months from the initiation of therapy. The 0–7–21 protocol was well-tolerated, and acute radiation reactions were low-grade and limited to the skin. The results of this study demonstrate that oral melanomas in dogs are responsive to radiation. 0–7–21 radiation therapy offers a viable alternative to radical excision, especially when tumor volume or location would require cosmetically or functionally debilitating surgery.     

Use of surgery and electron beam irradiation, with or without chemotherapy, for treatment of vaccine-associated sarcomas in cats: 78 cases (1996-2000).

OBJECTIVE: To evaluate responses of cats with vaccine-associated sarcomas to treatment with surgery and radiotherapy, with or without adjunctive chemotherapy. DESIGN: Retrospective study. ANIMALS: 76 cats (78 tumors). PROCEDURE: Medical records were reviewed. Factors potentially associated with survival time, time to recurrence, and time to development of metastases were evaluated. RESULTS: Following excision, electron beam radiation, and, in some cases, chemotherapy, 32 (41%) cats experienced recurrence, and 9 (12%) cats developed metastases. One- and 2-year survival rates were 86 and 44%, respectively. Median survival time from onset of disease was 730 days (range, 30 to 2,014 days). Median disease-free interval was 405 days (range, 30 to 925 days). Cats that underwent only 1 surgery prior to radiotherapy had a lower recurrence rate than did cats that underwent > 1 surgery and had a significantly longer disease-free interval. Survival time and disease-free interval decreased as time between surgery and the start of radiotherapy increased. Cats that developed metastases had significantly shorter survival times and disease-free intervals than did cats that did not develop metastases. Castrated male cats had a significantly shorter survival time than did spayed female cats. Cats with larger tumors prior to the first surgery had shorter survival times. Twenty-six cats received chemotherapy in addition to surgery and radiotherapy. Whether cats received chemotherapy was not associated with recurrence rate, metastasis rate, or survival time. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that excision followed by electron beam irradiation may be beneficial for treatment of cats with vaccine-associated sarcomas. Extent of excision prior to radiotherapy did not seem to be associated with recurrence rate.     

FAT NECROSIS SIMULATING RECURRENT NEOPLASIA FOLLOWING EXTERNAL BEAM RADIOTHERAPY IN A DOG

A 4.5-year-old neutered male dog was diagnosed with incompletely excised well-differentiated lymphangiosarcoma in the right inguinal subcutaneous region. The mass had metastasized to the right hypogastric and medial iliac lymph nodes. Surgery followed by definitive radiation therapy was administered to the primary site and the sites of metastasis. The dog had a complete response to radiotherapy, and minimal acute side effects. Doxorubicin was administered after radiotherapy. Approximately 4 months following radiation therapy, the dog developed a mass, presumed recurrent tumor, in the original site. In a biopsy only steatitis and fibrosis were found. The mass continued to grow and conservative surgical excision was elected. Histopathologically the diagnosis was fat necrosis and steatitis, with a microscopic focus of lymphangiosarcoma. Fat necrosis is an uncommon sequelum to breast irradiation in people and also appears to be rare in animals. Fat necrosis should be considered as a differential diagnosis when recurrent tumor is suspected in a previously irradiated subcutaneous site in a dog.     

Pancreatic beta cell tumor in a ferret

A ferret with clinical and laboratory signs of hypoglycemia was found at surgery to have a beta cell tumor of the pancreas. There had been recurrent episodes of weakness, ataxia, dehydration, and hypothermia. A fasting blood glucose content was 43 mg/dl and the amended insulin/glucose ratio was 362.5. The tumor was removed, yet hypoglycemia persisted postoperatively. Clinical signs related to hypoglycemia did not recur following application of medical treatment and frequent feedings. The histologic appearance of the tumor closely resembles that which has been seen in other species.     

RADIATION AND CISPLATIN FOR TREATMENT OF CANINE URINARY BLADDER CARCINOMA

Two cases of canine urinary bladder carcinoma were treated with combined radiation and cisplatin. Total radiation dose was 4400 cGy for one dog and 4800 cCy for the other. Cobalt 60 radiation was fractioned using 400 cGy per fraction. Cisplatin was administered intraarterially at a dose of 50 mg/m² divided equally six to seven hours before the first three radiation fractions. Cisplatin was administered before the last three radiation fractions at the same dose and time, but was infused intravenously. Objective evaluation using double contrast cystograms revealed reduction in tumor size in both dogs. The therapy was well-tolerated with minimal side effects.     

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.     

Treatment of hemangiopericytoma in a dog, using surgical excision, radiation, and a thoracic pedicle skin graft

A dog with hemangiopericytoma of the left forelimb underwent surgical excision followed by radiation therapy and thoracic pedicle skin grafting. Recurrence of the neoplasm was not observed 3.5 years after surgery. Hemangiopericytoma is an uncommon neoplasm that seldom metastasizes but has a high recurrence rate. In this dog, complete surgical excision was not possible because of the location and invasiveness of the neoplasm. The combination of surgery, radiotherapy, and skin grafting was a viable alternative to limb amputation.     

Surgical decompression,with or without adjunctive therapy,for palliative treatment of primary vertebral osteosarcoma in dogs

Vertebral osteosarcoma (OSA) is the most common primary vertebral tumor in dogs, however studies examining the survival time after surgical decompression of these tumors are limited. There is also limited information regarding the benefit of adjunctive treatments such as radiation therapy or chemotherapy in these patients. The goal of this study was to determine survival time of dogs with primary vertebral OSA after palliative decompressive surgery alone and combined with radiation therapy and/or chemotherapy. Records from 22 client‐owned dogs diagnosed with primary vertebral OSA and treated with decompressive surgery were collected retrospectively from eight referral institutions. Survival time was assessed for dogs treated with surgery alone as well as dogs who received adjunctive radiation therapy and/or chemotherapy. Median survival time in the 12 dogs treated with surgery alone was 42 days (range: 3‐1333 days). The three dogs treated with surgery and chemotherapy had a median survival time of 82 days (range: 56‐305 days). Only one dog was treated with surgery and radiation therapy; this dog survived 101 days. Six dogs were treated with surgery, radiation therapy and chemotherapy; these dogs had a median survival time of 261 days (range: 223‐653 days). Cause of death in all cases that survived the initial postoperative period was euthanasia secondary to confirmed or suspected tumor regrowth. The results of this study suggest that definitive radiation therapy, possibly combined with concurrent chemotherapy, significantly improves survival in dogs treated with palliative decompressive surgery for vertebral OSA and should be the treatment of choice in selected cases.     

Combined surgical and radiotherapy treatment of a mandibular ameloblastic carcinoma in a pony

A 9‐year‐old Welsh Section D gelding was referred to an equine hospital for evaluation and computed tomographic (CT) imaging of a left mandibular swelling. An expansile mass, found within the left mandible at the level of the caudal 2 cheek teeth, was surgically debulked and histology of the lesion identified it as an ameloblastic carcinoma. Radiotherapy using 4 fractions of 800 cGy, 7 days apart, was subsequently undertaken. The pony made excellent clinical progression following treatment. Repeat CT imaging at 7.5 and 19.5 months post surgery showed no apparent recurrence of the lesion and marked improvement in the remodelling of the mandible. In conclusion, radiotherapy in conjunction with surgical debulking appears to have been successful in treating an ameloblastic carcinoma in this pony and could be considered for similar tumours in other cases.     

192iridium brachytherapy, using an intracavitary afterload device, for treatment of intranasal neoplasms in dogs.

After surgical removal of a primary intranasal neoplasm, an implant device, designed to deliver 192iridium (192Ir) brachytherapy, was positioned in the nasal cavity of 8 dogs. Ribbons containing 192Ir seeds were placed in the device, using an afterloading technique. Dosimetry, to a dose of 7,000 to 10,000 centiGray (cGy), was calculated to encompass the site previously occupied by the tumor and a 1-cm margin of surrounding normal tissue. The quantity of 192Ir implanted varied between 16.69 and 100.80 mg of radium equivalent. The duration of implantation ranged from 90 to 168 hours. All dogs tolerated the implant well, but had a mucoid nasal discharge after radiotherapy. The implant device allowed rapid application and removal of the radioactive ribbons. Mean (+/- SD) radiation exposure to each radiotherapist during seed loading and unloading was 14.4 (+/- 5.3) and 4.5 (+/- 0.9) mrem, respectively. A uniform dose distribution around the intranasal implant device was achieved; however, dogs that received doses in excess of 9,400 cGy at the dorsolateral surface of the nose and/or hard palate had bone and soft tissue necrosis between 70 and 120 days after treatment. One dog was euthanatized 50 days after treatment because of metastatic disease, and 2 dogs were euthanatized because of local tumor recurrence at 125 and 212 days. Death, considered unrelated to treatment, occurred in 1 dog that was euthanatized 27 days after treatment and in 3 dogs that died 30, 93, and 456 days after treatment. Necropsy was performed on 3 of these dogs and evidence of intranasal neoplasia was not observed. One dog remained disease-free at 587 days after treatment.     

Radiotherapy of soft tissue sarcomas in dogs

Megavoltage radiotherapy was administered to 42 dogs with soft tissue sarcoma. Acceptable local control of these aggressive tumors was achieved after one year of treatment. Control rates of 48 and 67% were obtained at doses of 45 and 50 gray (Gy), respectively. At 2 years, control rates decreased to 33% at the dose of 50 Gy. Serious complications developed in 4 of 42 dogs at doses of 40 to 50 Gy. The estimated dose with a 50% probability for causing serious complications was 54 Gy, given in 10 fractions. We believe that the large doses per fraction used in this study probably led to an increased probability for necrosis. Hemangiopericytomas seemed to be more responsive than fibrosarcomas. Only 2 of 11 recurrent tumors were controlled with surgery. Good local control was achieved with radiation alone for one year at doses with a low probability for serious complications; however, higher total radiation doses or combined modalities, such as surgery and radiation or radiation and hyperthermia, may be needed for longer-term control.     

RESPONSE OF FELINE ORAL SQUAMOUS CELL CARCINOMA TO PALLIATIVE RADIATION THERAPY

Seven cats with advanced oral squamous cell carcinoma were treated with palliative radiotherapy. Megavoltage radiation in 8 Gray (Gy) fractions was delivered on days 0, 7, and 21 for a total dose of 24 Gy. Treatment field included the mandible, oropharynx, retropharyngeal lymph nodes, and tonsils. Adjuvant treatment with chemotherapy was variable. Age ranged from 13 to 18 years old with a median age of 15 years. Three of the seven cats (43%) did not complete treatment. Six cats were euthanized due to tumor growth and/or radiation side effects with a median survival time of 60 days (range = 42 to 97 days, mean = 63 +/- 8.4 days). Radiotherapy complications or progression of disease occurred in 6 of 7 (85.7 %) cats and included adverse clinical signs, such as mucositis, serosanguinous oral discharge, pain, and dysphagia. These data suggest that coarse fractionation radiotherapy did not result in palliation in cats with inoperable oral squamous cell carcinoma.     

Toxoplasma gondii brain granuloma in a cat: diagnosis using cytology from an intraoperative sample and sequential magnetic resonance imaging

A cat with a history of seizures and clinical suspicion of forebrain disorder underwent a brain magnetic resonance imaging. A space-occupying lesion was identified in the left temporal lobe. The mass was surgically removed, and cytological, histological and immunohistochemical examinations documented the presence of Toxoplasma gondii. A definitive diagnosis of an intracranial T gondii granuloma was made. The cat was treated with clindamycin and phenobarbital and the seizures did not recur. After 10 months, a second magnetic resonance imaging showed severe brain atrophy, but T gondii granuloma recurrence was not noted. Twenty-one months after surgery, the cat's condition deteriorated, and another magnetic resonance imaging showed a presumptive recurrence of T gondii granuloma. In cats, T gondii granuloma must be considered as a differential diagnosis even when only a single intracranial mass is present. Cytology and magnetic resonance imaging can be useful in making a definitive diagnosis and to follow the evolution of the lesion.     

Eosinophilic conjunctivitis, herpes virus and mast cell tumor of the third eyelid in a cat

A 3-year-old Himalayan cat was diagnosed with concurrent eosinophilic conjunctivitis, herpes virus, and a conjunctival mast cell tumor. Eosinophilic conjunctivitis was verified via cytology from a conjunctival scraping, which revealed 50% eosinophils and 50% neutrophils. Herpes virus was verified via a positive polymerase chain reaction (PCR). Conjunctival scrapings for chlamydia immmunofluorescent antibody (IFA) and herpes IFA were negative. A mycoplasma was detected by a general mycoplasma PCR but the organism did not grow on the available mycoplasma media. The mass was excised and microscopic evaluation revealed a histiocytic mast cell tumor. The mast cell did not recur following local excision (at 1 year follow-up). The eosinophilic conjunctivitis was treated with both topical steroids and systemic megesterol acetate (Ovaban). When topical steroids were used, the herpes virus flared up and resulted in dendritic and geographic corneal ulceration. Therefore, the cat was treated with megesterol acetate and the eosinophilic conjunctivitis was well controlled. Treatment of eosinophilic conjunctivitis in the cat with megesterol acetate may be the treatement of choice due to the possibility of herpes virus.