Use of radiation and/or hyperthermia for treatment of mast cell tumors and lymphosarcoma in dogs

Palliative Radiation Therapy for Treatment of Cutaneous T-cell Lymphoma in a Double Yellow-headed Amazon Parrot (Amazona oratrix)

A 17-year-old captive female double yellow-headed Amazon parrot (Amazona oratrix) was presented to the Kansas State University Zoological Medicine Service (Manhattan, KS, USA) for a 2-month history of a left sided facial swelling. On examination, a red, raised mass was noted on the left side of the face. A whole-body computed tomography scan of the bird was performed to assess the extent of the mass and evaluate the patient for obvious evidence of disseminated disease. No systemic involvement was detected, and the swelling was localized to the cutaneous and subcutaneous tissues overlying the left rhamphotheca. Two punch biopsies were collected, and histopathology was consistent with cutaneous lymphoma, with strong positive CD3 staining congruous with a T-cell origin. Because of a lack of evidence for disseminated disease, the authors elected to pursue localized radiation therapy, and a single fraction of 8 Gray was administered. The swelling had resolved by the time of the recheck examination 4 weeks post-radiation therapy, and the patient remained clinically normal 52 weeks after radiation therapy.

Canine and Feline Cutaneous Mast Cell Tumor: A Comprehensive Review of Treatments and Outcomes

Mast cell tumor (MCT) or mastocytoma is one of the most frequent malignant cutaneous tumors in the dog, and the second most frequent in the cat. Several mast cell tumor therapeutic approaches have been proposed in the past years for dogs and cats, resulting in very distinct outcomes. The current comprehensive literature review presents a critical approach to the scientific information published about the MCTs treatments and the subsequent prognosis and survival times, in dogs and in cats diagnosed with MCTs. A systematic review of the literature following the Cochrane principles and methodology was performed. The authors resorted to MEDLINE, Scopus, Google Scholar and Web of Science databases to select the 133 publications with evidence-based treatments for MCTs in companion animals. Results of the review suggest that the recommended treatment, prognosis and survival times for dogs and cats with MCTs depends at all times on the clinical staging, histological grade and location of the tumor.

Survival analysis of 97 cats with nasal lymphoma: a multi-institutional retrospective study (1986-2006)

BACKGROUND

Feline nasal lymphoma (NLSA) is a condition for which no standard of care exists.

HYPOTHESIS

There is no difference in survival times of cats with NLSA treated with single or multimodality therapy.

ANIMALS

Records from 97 cats diagnosed with NLSA were examined.

METHODS

The purpose of this retrospective study was to compare the survival times of cats with NLSA treated with radiation therapy (RT) alone, chemotherapy alone, or RT + chemotherapy and identify potential prognostic variables that affected survival. Cats were grouped according to therapy: RT + chemotherapy (n = 60), RT alone (n = 19), or chemotherapy alone (n = 18).

RESULTS

Survival was calculated with 2 methods. The 1st survival analysis (method A) included all cats, but counted only deaths caused by progressive NLSA. The median survival time (MST), regardless of therapy modality, was 536 days. The 2nd survival analysis (method B) also included all cats and counted all deaths, regardless of cause, as events. The overall MST calculated for all deaths was 172 days. A negative independent prognostic variable identified was anemia (P < .001), and positive independent prognostic variables were a complete response to therapy (P < .001) and total radiation dose >32 Gy (P= .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

There were no significant differences in survival times among the 3 treatment groups but these results suggest that the addition of higher doses of RT to a cat's treatment protocol may control local disease and therefore influence survival.

Mast cells and canine mast cell tumours. A review

This article reviews the literature on mast cells and tumours derived from mast cells in the dog. Mast cells play a central role in inflammatory and immune reactions. Mast cells, normal and neoplastic, contain and release important biologically active substances: heparin, histamine, eosinophilic chemotactic factor and proteolytic enzymes. Mast cell tumours occur in the dog, particularly in the boxer and related breeds, in the skin and less frequently in the intestines. Cytology usually provides an accurate diagnosis, but histological examination adds further information concerning the histologic grade and the completeness of surgical therapy. Cutaneous mast cell tumours should be regarded as potentially malignant and therefore be removed widely (3 cm. margin). Local recurrence, regional and distant metastases together with paraneoplastic disorders may cause the death of the pet. Histologic grading (2 or 3 grades) and clinical staging together with kinetic parameters and breed (boxers have relatively benign tumours) are important prognostic parameters. Based on prognostic criteria, surgical treatment should be completed with adjuvant radiotherapy, corticosteroids and eventually with combined chemotherapy. A novel, promising therapy is the application of the receptor kinase inhibitor. The study of the pathogenesis of mast cell tumours received new impetus by the finding of mutations, deletions and duplications, in exons 11 and 12 of the C-kit oncogene. Further study of physiological and oncological aspects of mast cells are favoured by the availability of mast cells isolated from spontaneous mast cell tumours and of cultured cell lines.

Solitary Nonepitheliotropic T-Cell Lymphoma in a Dog

A 7-year-old male Golden Retriever with swelling of the rostral bridge and right wing of the nasal areas, sneezing, and inspiratory difficulty was referred to a neighbor veterinarian. Except for those in the nasal area, no lesions were noted during routine physical examination. The mass occupying the nasal cavity was not observed radiographically. Punch biopsy of the affected lesions revealed nonepitheliotropic lymphoma. Immunohistochemical staining for CD3 antigen was positive. The dog was diagnosed with solitary nonepitheliotropic T-cell lymphoma. Local radiotherapy and systemic chemotherapy with doxorubicin were instituted and resulted in total clinical remission. The dog has remained disease free for 30 months.

Radiation therapy for incompletely resected canine mast cell tumors

The records of 56 dogs treated with megavoltage radiation for mast cell neoplasia were reviewed to determine the efficacy of this treatment modality. Total radiation dose ranged from 45 to 57 Gray (Gy), dose per fraction ranged from 3.0 to 4.0 Gy, and radiation treatment time ranged from 14-28 days. Median disease free interval (95% CI) was 32.7 (19-70) months. Median disease free interval for dogs older than 7.5 years was 15 (lower limit 7) months as compared to 62 (lower limit 20) for dogs younger than 7.5 years of age (p = 0.006). Median disease free interval for dogs with measurable disease was 12 (lower limit 5) months as compared to 54 (32-70) months for dogs with microscopic disease (p = 0.006). Radiation treatment time was also significantly related to disease free interval. Median disease free interval for dogs treated longer than 22 days was 12 (7-19) months as compared to greater than 50 (lower limit 20) months for dogs treated in 22 or fewer days (p < 0.001). This appeared to be due to more recurrences in dogs treated with 3-per-week fractionation and suggests that tumor proliferation in the interfraction interval may be important. Sex, tumor location, histologic grade, WHO clinical stage, number of radiation fractions, total radiation dose, and dose-per-fraction, as well as the following "yes/no" variables: steroids given, surgery prior to radiation, lymph nodes irradiated, and development of another mast cell tumor did not appear to influence median disease free interval or survival. Data presented herein support megavoltage radiation as an effective treatment for canine mast cell neoplasia, and suggest that disease free interval in dogs treated with daily fractions may be longer than that achieved with alternating day fractions.

The role of radiotherapy in the treatment of lymphoma and thymoma

Chemotherapy is the mainstay of therapy for the treatment of lymphoma in dogs and cats. Radiation therapy can be utilized in the management of patients with solitary lymphoma and to induce a rapid local response in selected patients with multicentric lymphoma. A combination of surgery and radiation therapy can offer an excellent prognosis for cats with thymoma. Radiation therapy can also play a role in the management of dogs with thymoma.

A prospective study of radiation therapy for the treatment of grade 2 mast cell tumors in 32 dogs

Surgery, chemotherapy, and irradiation have been used singly or in combination to treat dogs with cutaneous grade-2 mast cell tumors (MCT). However, optimal treatment has not been established. At The Animal Medical Center, 32 dogs with grade 2, stage 0 MCT received cobalt radiation treatment to a dose of 54 Gy; 94% had a disease-free interval of 1 year. The 2-,3-,4-, and 5-year disease-free intervals were 86%. Survival rates were 100% for 1 year and 96% for 2 to 5 years, with only 1 death caused by MCT. Primary site was not a prognostic factor for survival in this study. Minimal toxicity was observed and was limited to acute cutaneous reactions. Late-term reactions to radiation therapy were mild and considered acceptable in all cases. No deaths occurred due to treatment, and no dog was eliminated from the study because of radiation therapy toxicity. Radiation therapy appears to be an effective treatment for dogs with grade 2, stage 0 MCT.

Clinical indications and applications of radiotherapy and hyperthermia in veterinary oncology

The response of dogs and cats with neoplasia to radiation therapy has improved significantly during the past 10 years. This has largely been due to more aggressive radiation therapy treatment schedules, more accurate planning, and refinement of clinical indications. Sufficient numbers of dogs and cats irradiated with curative intent have not been accumulated to yet define the full impact of more aggressive therapy. However, many tumors will likely remain resistant to irradiation because of concomitant normal tissue injury that must be minimized. Systematic investigation of combination therapy (surgery, radiation, chemotherapy, and hyperthermia) should succeed in reducing local tissue side effects and increased local tumor control. A comprehensive approach to tumor management begins with decisions thoughtful of optimal treatment for suspected malignant tumors even at the time of initial examination and client counseling. An incisional biopsy provides essential information to determine the therapeutic course and should be considered prior to initial excision. More aggressive treatment, of even small tumors, early in the clinical course will lead to prolonged tumor control. Radiation therapy should be considered fundamental in the comprehensive treatment plan of many solid tumors.

Canine mast cell tumors

Mast cell tumors (MCTs) are common in the dog, occurring most frequently in the skin and subcutaneous tissues. Their biologic behavior can be quite variable, with approximately 50% being malignant. Although clinical features and histologic grading can help determine the likelihood of malignancy, it is difficult to predict the biologic behavior of an individual tumor. Consequently, all MCTs should be considered potentially malignant. Wide surgical excision is the most common therapy for canine MCTs, although approximately 50% recur locally. Nonresectable or recurrent MCTs can be treated with radiation and/or chemotherapy. Chemotherapy is also used in the treatment of metastatic MCTs, and it may be helpful in preventing the recurrence and/or metastasis of undifferentiated tumors.