Intranasal melanoma treated with radiation therapy in three dogs

Melanoma of the dog and cat: consensus and guidelines

Melanoma of the dog and cat poses a clinical challenge to veterinary practitioners across the globe. As knowledge evolves, so too do clinical practices. However, there remain uncertainties and controversies. There is value for the veterinary community at large in the generation of a contemporary wide-ranging guideline document. The aim of this project was therefore to assimilate the available published knowledge into a single accessible referenced resource and to provide expert clinical guidance to support professional colleagues as they navigate current melanoma challenges and controversies. Melanocytic tumors are common in dogs but rare in cats. The history and clinical signs relate to the anatomic site of the melanoma. Oral and subungual malignant melanomas are the most common malignant types in dogs. While many melanocytic tumors are heavily pigmented, making diagnosis relatively straightforward, melanin pigmentation is variable. A validated clinical stage scheme has been defined for canine oral melanoma. For all other locations and for feline melanoma, TNM-based staging applies. Certain histological characteristics have been shown to bear prognostic significance and can thus prove instructive in clinical decision making. Surgical resection using wide margins is currently the mainstay of therapy for the local control of melanomas, regardless of primary location. Radiotherapy forms an integral part of the management of canine oral melanomas, both as a primary and an adjuvant therapy. Adjuvant immunotherapy or chemotherapy is offered to patients at high risk of developing distant metastasis. Location is the major prognostic factor, although it is not completely predictive of local invasiveness and metastatic potential. There are no specific guidelines regarding referral considerations for dogs with melanoma, as this is likely based on a multitude of factors. The ultimate goal is to provide the best options for patients to extend quality of life and survival, either within the primary care or referral hospital setting.

Feasibility of low-dose CT protocols for evaluating the sinonasal cavity and reducing radiation exposure in dogs

With the increasing use of radiation therapy for treatment of canine sinonasal neoplasia, there is a need for developing low-dose CT protocols to help minimize radiation exposure. The purpose of this study was to assess the trade-off between image quality and reduced radiation exposure of a low-dose CT technique in the canine sinonasal cavity. In this prospective, experimental study, CT images of the sinonasal cavities from 10 normal Beagles were acquired using high-dose (130 kVp) or low-dose (110 kVp, 80 kVp) protocol. Radiation dose and image quality were compared. Radiation exposure measured by the volume-weighted CT dose index and dose-length product was reduced by 36% at 110 kVp and 74% at 80 kVp respectively, compared to the corresponding values at 130 kVp (P = 0.000). Low-dose protocol resulted in higher image noise and reduced signal-to-noise ratio and contrast-to-noise ratio than 130 kVp in most evaluated regions of interest (P < 0.05). CT numbers of the contrast-enhanced structures were highest at 80 kVp (P = 0.000). Conspicuity of most sinonasal structures was similar for high dose and both lower dose protocols. The results of this study indicate that 80 or 110 kVp can be used for sinonasal CT examinations to reduce radiation exposure to the patient without compromising image quality.

Malignant Melanoma in a Long-legged Buzzard (Buteo rufinus): Characterization of Clinical and Histologic Lesions

A 17-year-old, male long-legged buzzard (Buteo rufinus) presented for acute lethargy and black gelatinous tissue in both nostrils. Despite intensive care, the bird died within 2 days. A postmortem computed tomographic scan of the head revealed a complete obstruction of the rostral infraorbital sinus, later confirmed by necropsy. Postmortem examination also highlighted multifocal, black, infiltrating nodules of various sizes (2 mm to 2 cm in diameter) in almost all internal organs: lungs, heart (pericardium, myocardium, endocardium), kidneys, pancreas, adrenals, muscles, and bones (periosteum and medulla). Histologically, the nodules were composed of anaplastic cells containing abundant melanin pigment, consistent with a disseminated melanoma. Malignant melanomas are aggressive neoplasms frequently reported in mammals but rarely found in avian species. In Accipitridae and Falconidae, only 2 cases have been reported.

Primary sinonasal malignant melanoma with systemic metastasis in a non-gray horse

A 27-y-old Anglo-Arabian gelding with bay coat color was presented with a swelling of the left maxillary region. Fenestration on the left maxilla revealed that the left maxillary sinus was filled with black-red tissue. A portion of the tissue was excised and diagnosed histologically as malignant melanoma. Genotyping of the STX17 gene for gray coat color revealed that the horse did not have the "gray" factor. The horse was euthanized ~3 mo after first presentation. During autopsy, a black-to-gray mass extended from the left nasal cavity to the surrounding paranasal sinus and invaded the hard palate, cribriform plate, and the cranial portion of the left olfactory bulb. Moreover, identical black nodules were present in lymph nodes from the mandible to the larynx, and in the spleen, liver, kidney, and adrenal glands. However, masses were not found in the skin, perineal region, or pelvic cavity. All of the black-to-gray nodules were malignant melanomas that were histologically identical to the initial biopsy; tumor emboli were also found in the kidney. Sinonasal mucosal melanoma is a rare disease in horses.

Outcome of external beam radiotherapy for treatment of noncutaneous tumors of the head in horses: 32 cases (1999-2015)

Background

The long‐term outcomes of external beam radiotherapy for treatment of noncutaneous tumors of the head in horses is unknown.

Objective

To report the long‐term outcomes for treatment of noncutaneous tumors of the head of horses, and report short and long‐term clinical adverse effects.

Animals

Thirty‐two horses treated in 2 referral hospitals.

Methods

In this retrospective study, medical records of horses receiving radiation therapy for noncutaneous tumors between 1999 and 2015 were reviewed. Signalment, tumor type, treatment protocol, tumor control duration, and survival were recorded. Kaplan‐Meier survival curves were generated for overall survival (OS), by tumor type and location, and compared using Log‐rank tests, and treatment protocol adherence.

Results

Follow‐up ranged from 2 to 145 months (median 14 months). Of 32 horses, 16 (50%) were alive at the time of reporting, with complete tumor response occurring in 12 (38%). Horses with tumors of the maxilla/nasal cavity had significantly shorter median OS compared to horses with tumors in other locations (21 months vs 145 months) (P = .06). Adverse effects resulting from the tumor or the therapy occurred in 20/32 (63%). The occurrence of major adverse effects and delays in treatment protocol were not significantly associated with median survival estimates.

Conclusions and Clinical Importance

External beam radiotherapy can be used to treat a variety of noncutaneous tumors of the head of horses. Adverse effects related to radiotherapy or the tumor are common.

Treatment of nasal tumours in dogs: a review

Nasal tumours are common neoplasms in dogs and often represent a diagnostic and therapeutic challenge due to their confined location within the nasal cavities. The main goal of this review is to extract the most relevant information from a wide and often confusing evidence-based medicine on the treatment of canine nasal tumours and conclude with current recommendations. This report highlights the different therapeutic modalities available and describes their technical aspects, interests and limitations. Megavoltage radiotherapy, as the most recent treatment and standard of care, is particularly examined, especially the different types of radiotherapy units, the main protocols used and their advantages and limits. Newer and non-conventional treatments are also discussed.

Canine Melanomas as Models for Human Melanomas: Clinical, Histological, and Genetic Comparison

Despite recent genetic advances and numerous ongoing therapeutic trials, malignant melanoma remains fatal, and prognostic factors as well as more efficient treatments are needed. The development of such research strongly depends on the availability of appropriate models recapitulating all the features of human melanoma. The concept of comparative oncology, with the use of spontaneous canine models has recently acquired a unique value as a translational model. Canine malignant melanomas are naturally occurring cancers presenting striking homologies with human melanomas. As for many other cancers, dogs present surprising breed predispositions and higher frequency of certain subtypes per breed. Oral melanomas, which are much more frequent and highly severe in dogs and cutaneous melanomas with severe digital forms or uveal subtypes are subtypes presenting relevant homologies with their human counterparts, thus constituting close models for these human melanoma subtypes. This review addresses how canine and human melanoma subtypes compare based on their epidemiological, clinical, histological, and genetic characteristics, and how comparative oncology approaches can provide insights into rare and poorly characterized melanoma subtypes in humans that are frequent and breed-specific in dogs. We propose canine malignant melanomas as models for rare non-UV-induced human melanomas, especially mucosal melanomas. Naturally affected dogs offer the opportunity to decipher the genetics at both germline and somatic levels and to explore therapeutic options, with the dog entering preclinical trials as human patients, benefiting both dogs and humans.