lauren askin, dvm, dacvr (radiation oncology...
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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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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.
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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