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Lauren Askin, DVM, DACVR (Radiation Oncology)

Veterinary Specialist

Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

VCAWLAspecialty.com

Etiology/Pathophysiology

Nasal tumors are locally invasive tumors that carry a

relatively low metastatic rate. Metastasis at the time of

diagnosis is seen in approximately 10% of animals, but

may be as high as 40-50% at the time of death. Death,

however, is usually attributable to local disease

progression rather than metastatic lesions. Most

common sites of metastasis are the regional lymph

nodes and lungs. Less common sites include bones,

kidneys, liver, skin, and brain.

Carcinomas, including adenocarcinoma, squamous cell

carcinoma, and undifferentiated carcinoma comprise

nearly two-thirds of nasal tumors in the dog; while

sarcomas, including fibrosarcoma, chondrosarcoma,

osteosarcoma, and undifferentiated sarcomas

comprise the bulk of the remaining tumors. In the cat, lymphoma and carcinoma are the

most common tumors of the nasal cavity.

Epidemiology/Signalment

Canine nasal tumors account for approximately 1% of all neoplasms in dogs. The average

age at the time of diagnosis is 10 years, and medium and large breed dogs may be more

commonly affected. A slight male predilection has been suggested, and doliochocephalic

breeds may be at an increased risk. It has also been speculated that dogs living in urban

environments with an increased risk of nasal filtering of pollutants may be at a higher risk.

Some studies have associated the exposure of environmental tobacco smoke with an

increased risk of cancer of the nasal cavity, but this finding is not consistent.

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Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

History and Clinical Signs

The most common clinical signs associated with nasal tumors include epistaxis, bloody or

mucopurulent nasal discharge, facial deformity from bone erosion and subcutaneous

extension, sneezing, dyspnea, stertorous breathing, exopthalmus, and ocular discharge

secondary to obstruction of nasolacrimal duct. The average duration of clinical signs

before diagnosis is 3 months. All of these clinical signs can overlap with other intranasal

diseases, but a strong suspicion for cancer should be made in older animals, with an

intermittent and progressive history of initially unilateral and/or mucopurulent discharge.

Diagnosis

Definitive diagnosis of a nasal tumor requires a tissue biopsy; however, historical

information and diagnostic imaging can be highly suggestive of cancer. Conventional

radiography can have a place in the diagnostic workup of dogs, but a CT s preferred as it

provides improved anatomic detail, which allows accurate determination of the extent of

the tumor for staging purposes and localization of nasal cavity abnormalities. A CT scan

also allows visualization of the cribiform plate to evaluate for tumor extension into the

cranial vault. Certain findings on CT are correlated with a diagnosis of cancer in dog, but

none of these alone or in combination are definitively diagnostic, and a tissue biopsy is

always needed for confirmation. Once a definitive diagnosis of a nasal tumor has been

made, fine needle aspirates of regional lymph nodes should be completed, along with

three-view chest radiographs to evaluate for pulmonary metastatic disease.

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A sagittal and axial image of the nasal cavity

showing a large left sided destructive mass.

Histopathology conformed adenocarcinoma.

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continued

Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

Several staging systems based on radiographic or CT findings have been proposed in

canine nasal tumors based on local tumor extent and bony erosion, but there prognostic

significance remains controversial. The Adams modified staging system developed in

2009 is the most recent staging system that has been adapted. With this staging system,

in a study of 94 dogs, with was found that dogs with unilateral intranasal involvement

without bone destruction beyond the turbinates on CT treated with definitive radiation had

the longest median survival time of 23.4 months; and patients with cribiform involvement

on CT had the shortest median survival time of 6.7 months.

Therapy for Canine Nasal Tumors

Treatment of nasal tumors is directed primarily

at the control of local disease; and unfortunately,

many times disease is extensive at the time of

diagnosis. Curative surgery is virtually

impossible as bony invasion occurs early in the

course of the disease. The combination of a

cytoreductive surgery followed by radiation

therapy for the treatment of nasal tumors has

also been evaluated, but this combination of

treatment has not been shown to improve the

clinical outcome in dogs when compared to

those treated with high-energy megavoltage

radiation alone.

Definitive, or curative intent radiation therapy, is

the treatment of choice for nasal tumors. A

definitive radiation protocol typically involves

doses of 40 to 54 Gy deliver in 10 to 18

treatments of 3 to 4.2 Gy over a 2 to 4 week

period. Computerized treatment planning using

CT images of the patient are recommended

when treating nasal tumors with definitive

radiation therapy. Computerized treatment

planning using CT images of the patient in

position can greatly enhance normal tissue sparing while ensuring appropriate dose

distributions within the tumor.

continued

The same patient positioned for radiation

therapy with an external immobilization

device to assure precise delivery of

electrons via the linear accelerator.

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Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

With definitive radiation protocols, acute toxicities are seen which involve the rapidly

dividing tissue of the oral cavity, nasal cavity, skin, and eye. Generally radiation side

effects are more serious with larger treatment fields, but it is important to plan an

adequate margin to achieve control of the tumor. The acute side effects develop and

progress during the course of treatment and resolve within about 2 to 8 weeks after

therapy. These side effects can be very severe with definitive radiation of the nasal cavity,

and oral antibiotics, pain medication, and/or artificial tears may be needed to support the

patient until the effects resolve. If oral mucositis is severe and the patient is unwilling to

eat, feeding tubes may be necessary in the short term. Late radiation side effects are less

common than acute side effects, but much more detrimental as they are permanent.

Development of late side effects should be prevented, if possible, with appropriate

treatment planning. These include effects to the eye, neuronal tissue, bone, and skin.

With radiation therapy, the goal of treatment is to deliver the maximum radiation dose to

the tumor, while minimizing the dose to the surrounding normal tissues. Most radiation

therapy done in veterinary medicine involves the use of conventional computerized

treatment planning. However, with the advances that have been made in the field of

radiation oncology, the use of intensity modulated radiation therapy (IMRT) has proven to

be a very good option of the treatment of canine nasal tumors. IMRT allows optimization

of radiation dose delivery to complex tumor volumes with rapid dose drop-off to

surrounding normal tissues. When IMRT is used, normal tissue toxicities are greatly

reduced and control times of nasal tumors are similar to conventional radiation treatments.

With IMRT, canine nasal tumors can potentially be treated with higher cumulative doses of

radiation without increasing acute or delayed toxicity beyond levels that are currently

considered acceptable.

Palliative radiation therapy can also be considered for the treatment of nasal tumors,

especially for patients with other underlying disease conditions, or in those patients with

advanced disease. With palliative radiation protocols, side effects are limited. Alleviation

of clinical signs has been reported in up to 95% of dogs treated with palliative radiation

with median survival times reported to be approximately 6-7 months. Chemotherapy has

also been evaluated for the treatment of nasal tumors in dogs. Clinical responses are

seen with chemotherapy, but the response is usually not durable.

Prognosis for Canine Nasal Tumors

The long term prognosis for dogs with nasal tumors is very dependent on the treatment

pursued. A retrospective study of 139 dogs with nasal tumor evaluated patients not

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Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

pursuing any treatment and the overall median survival time was only approximately 3

months. This study also found that the dogs presenting with epistaxis had a significantly

shorter median survival time than dogs without epistaxis. Studies evaluated surgery as the

sole treatment of nasal tumors report median survival times of only 3-6 months, and the

surgeries have been associated with a high rate of acute and chronic morbidity. When

high-energy megavoltage radiation is used alone with curative intent, median survival

times have been reported to range from 8-19.7 months, with 1- and 2-year survival rates

ranging from 43% to 60% and 11% to 44%, respectively. The combination of surgery

followed by post-operative radiation reports survival times ranging from 4.1 months to 15.2

months; therefore, adding no benefit to radiation therapy alone. A small series of 13 dogs

reported on full-course preoperative radiation therapy followed by surgical exteneration of

residual or recurrent disease. This treatment did show promise when compared to

radiation alone with these dogs having a median survival time of 47 months; however,

these patient experienced significant late side effects including rhinitis (bacterial and

fungal), osteomyelitis, and fistula formation. A larger group of dogs must be treated to

confirm these findings. More recent studies evaluating the use of IMRT have reported

survival times consistent with those previously reported, with moderate to severe side

effects being uncommon except in the eye ipsilateral to the bulk of the tumor and in the

skin of patients that had facial deformity.

Prognosis for Feline Nasal Tumors

Reports of treatment for feline nasal tumors are

few and case numbers are small. In the largest

published study, 16 cats with

nonlymphoproliferative neoplasms were treated

using a definitive course of radiation to a total

dose of 48 Gy. This treatment resulted in minimal

acute side effects and modest chronic ocular side

effects with a median survival time of 12 months.

When radiation therapy protocols are used for the

treatment of feline nasal lymphoma, long term

control of local disease is favorable; and it has

been reported that higher total doses (greater or equal to 32 Gy) of radiation therapy may

confer an additional survival benefit. The role of chemotherapy for the treatment of feline

nasal lymphoma is undefined, but it should be considered, because multimodality therapy

typically is the optimal choice for treating local disease plus disseminated spread or

microscopic disease. Median survival times for cats receiving radiation therapy +/-

chemotherapy for the treatment of nasal lymphoma ranges from 13-31 months.

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Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

Cancer of the Nasal Planum

Cancer of the nasal planum is rare in the dog and relatively common in the cat. The most

common cancer of the nasal planum is squamous cell carcinoma. In dogs, infiltrative SCC

of the nasal planum is more difficult to manage than in the cat. In the dog, recurrence is

likely following surgical excision and radiation therapy. In the cat, invasive cancer of the

nasal planum can be completely excised with an acceptable cosmetic result. More than

80% of cats with invasive SCC of the nasal planum treated with a nosectomy are free of

recurrent disease at 1 year. The outlook for non-invasive, early SCC is good, with control

times reported to be approximately 5 years, however, development of neoplasia on other

areas of the nasal planum after localized treatment is common.

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Radiation Oncology

VCA West Los Angeles Animal Hospital

1900 S. Sepulveda Boulevard

Los Angeles, CA 90025

P 310-473-2951 | F 310-979-5400

Dr. Lauren Askin was born and raised in West Virginia. She attended

the University of Delaware where she received her Bachelor’s degree in

Animal Science in May 2005. She earned her DVM at the University of

Georgia in 2009. Following completion of Veterinary School, she

completed a one-year small animal medical and surgical internship at

VCA West Los Angeles. Dr. Askin completed a 2-year residency in

Radiation Oncology at North Carolina State University and is board

certified in veterinary radiation oncology. Dr. Askin’s interests include

advanced radiation therapy techniques to improve local tumor control

and reduce treatment related side effects.

Lauren Askin, DVM, DACVR

(Radiation Oncology)

Veterinary Specialist

VCA West Los Angeles Animal Hospital