Page 1319 - Clinical Small Animal Internal Medicine

137 Cancer of the Nose and Mouth 1257

Nasal tumors are locally invasive tumors that carry a Several staging systems based on radiographic or
VetBooks.ir relatively low metastatic rate. Metastasis at the time of CT findings have been proposed in canine nasal
tumors but their prognostic significance remains
diagnosis is seen in approximately 10% of animals, but
may be as high as 40–50% at the time of death. Death,
developed in 2009 is the most recent system that has
however, is usually attributable to local disease progres- controversial. The Adams modified staging system
sion rather than metastatic lesions. Most common sites been adapted (Table 137.2). With this system, dogs
of metastasis are the regional lymph nodes and lungs. with unilateral intranasal involvement confined to the
Less common sites include bones, kidneys, liver, skin, nasal cavity had the longest median survival time of
and brain. 23.4 months when treated with definitive radiother-
apy. Those with cribriform involvement had the
Epidemiology shortest median survival time of 6.7 months.

Nasal tumors account for approximately 1% of all neo-
plasms in dogs and cats. Therapy
Treatment of nasal tumors is directed primarily at the
Signalment control of local disease. Unfortunately, the disease is often
extensive. Curative surgery is not possible as bone inva-
The average age at the time of diagnosis for canine and sion occurs early in the course of the disease. Hence, radi-
feline nasal tumors is 10 years. It appears that medium‐ ation therapy is the standard of care. The combination of a
and large‐breed dogs may be more commonly affected. cytoreductive surgery followed by radiation therapy for
Also, a slight male predilection has been suggested in dogs, the treatment of nasal tumors has been evaluated, but has
and dolichocephalic breeds may be at an increased risk. not been shown to improve clinical outcome in dogs when
compared to megavoltage radiation alone.
History and Clinical Signs With definitive or curative intent radiation, the goal of
treatment is to deliver the maximum radiation dose to the
The most common clinical signs associated with nasal tumor while minimizing the dose to surrounding normal
tumors include epistaxis, bloody or mucopurulent nasal tissues. Most radiation therapy done in veterinary medi-
discharge, facial deformity, sneezing, dyspnea, sterto- cine involves the use of conventional computerized treat-
rous breathing, exophthalmia, and ocular discharge sec- ment planning. However, with advances in the field of
ondary to obstruction of the nasolacrimal duct. The radiation oncology, the use of intensity-modulated radia-
average duration of clinical signs before diagnosis is tion therapy (IMRT) has proven to be a very good option
three months. All of these clinical signs can overlap with for the treatment of nasal tumors. IMRT allows for the
other intranasal diseases, but a strong suspicion for can- optimization of radiation dose delivery to complex tumor
cer should be made in older animals with an intermittent volumes with rapid dose drop-off to surrounding normal
and progressive history of initially unilateral and/or tissues. When IMRT is used, normal tissue toxicities are
mucopurulent discharge. greatly reduced while higher cumulative doses of radiation
are delivered to the tumor. Traditional definitive protocols
Diagnosis involve the administration of a total radiation dose of 40-57
Gy in 10-19 fractions of 3-4.2 Gy, over a 2-4 week period.
Definitive diagnosis of a nasal tumor requires a tissue
biopsy but historical information and diagnostic imaging Table 137.2 Adams 2009 modified staging system for canine
can be highly suggestive of cancer. Conventional radiog- nasal tumors
raphy can be helpful in the diagnostic evaluation of dogs,
but CT is preferred as it provides improved anatomic Stage Remarks
detail, determination of the extent of the tumor, and
identification of nasal cavity abnormalities. A CT scan T1 Confined to one nasal passage, paranasal sinus, or
also allows for detection of CNS invasion. Certain find- frontal sinus with no bony involvement
ings on CT are correlated with a diagnosis of cancer in T2 Any bony involvement, but no evidence of orbital,
dogs, but none of these alone or in combination are subcutaneous, or submucosal mass
definitively diagnostic. A tissue biopsy is always required. T3 Involvement of orbit or subcutaneous or
Once a definitive diagnosis has been made, fine needle submucosal mass
aspirates of regional lymph nodes should be completed, T4 Tumor extension into the nasopharynx or
along with three‐view thoracic radiographs. cribriform plate