When it comes to nasal tumors, the nose knows

Long-nosed dogs, such as greyhounds, are more commonly affected with nasal tumors. (Getty Images)

Nasal neoplasia can be difficult to treat because by the time it is diagnosed, the disease is often advanced. Nasal tumors inside the cavity can be insidious, staying hidden for months before becoming symptomatic, says Timothy Fan, DVM, PhD, DACVIM (oncology), principal investigator of the Comparative Oncology Research Laboratory at the University of Illinois College of Veterinary Medicine. By separating nasal cancer into two main groups, neoplasia of the nasal planum and neoplasia of the nasal cavity, we can divide and conquer these diseases.

Nasal planum neoplasia

The nasal planum consists of stratified nonhaired epithelium of the nose. Cancer of this area is less common in dogs and more common in cats-ultraviolet (UV)-induced squamous cell carcinoma (SCC) being the most common, says Fan.

UV-induced SCC starts out as a nonhealing wound. The human equivalent to this stage is actinic keratosis or solar dermatitis and is deemed a dermatologic condition. It's not cancer yet! These precancerous lesions progress to carcinoma in situ, where cells have developed hyperplastic characteristics but haven't adopted an aggressive, invasive phenotype yet, says Fan. After this stage comes carcinoma, where the cells become invasive to surrounding tissues.

If disease is diagnosed in the multicentric carcinoma in situ and actinic keratoses state, there is some evidence that using an 5% imiquimod cream on the lesions can treat the condition.1,2 While imiquimod cream has been tested on SCC in cats, it is not labeled for use in cats, and it can be difficult to keep the cat from licking off the cream. However, Fan says it is an option to consider in cats for which surgery or radiation therapy is not an option.

Typical therapies for SCC once it has proceeded to the malignant stage include surgical excision, radiation therapy, YAG laser treatment and cryotherapy.

The curse of the long nose

In dogs, nasal cavity neoplasms are most commonly diagnosed in geriatric medium- to large-breed mesocephalics and dolichocephalics, says Fan. While there is no study explaining why nasal cavity tumors are found more in long-nosed dogs than short-nosed dogs, the theory is if you have more nose, you have more cells. If you have more cells, there is a higher opportunity for mutation. In addition, the nose filters out carcinogens. If a dog has a long nose with greater surface area that is exposed to carcinogenic substances, that also increases the risk of mutation.

Nasal cavity neoplasia

The nose acts as a filter, preventing inhaled particles from reaching small alveoli in the lungs. It is also a remarkable sensory organ and is the most important sensory organ in dogs.

Nasal cavity tumors are typically locally invasive and destroy underlying bone. They are less likely to metastasize, but nasal cavity tumors can still spread to regional lymph nodes in late-stage disease. If a dog has metastatic disease, the survival time decreases from 400 days to 100 days.3

In dogs, two-thirds to three-fourths of nasal cavity neoplasms are carcinomas and one-fourth to one-third are diagnosed as sarcomas, chondrosarcoma being the most common, says Fan. Lymphoma, transmissible venereal tumor, polyps and papillomas are considered rare.

In cats, the most common nasal cavity tumors include SCC, carcinoma and lymphoma. Nasal lymphoma in cats is not associated with feline leukemia virus or feline immunodeficiency virus, and generally responds well to conventional treatment (ionizing radiation and/or systemic chemotherapy) and has a low metastatic rate, says Fan.

Diagnosis. Despite the location, nasal cavity neoplasia can be relatively easy to diagnose. It has a classic history-slow progression, some sneezing but not paroxysmal, nasal discharge and unilateral epistaxis, says Fan. The condition can improve with systemic antibiotics but usually returns. In the late stages, these dogs are painful: eyes closed, head hung low. Fan says there can be massive nasal deformation or fistulas, exophthalmos and regional lymphadenopathy.

The differential list includes nasal neoplasia fungal rhinitis (Aspergillus species in dogs, Cryptococcus neoformans in cats), foreign body, tooth root abscess, coagulopathies, systemic hypertension and nonfungal infection such as nasal mites or bacterial rhinitis.

On physical examination, Fans recommends checking for facial symmetry, retropulsing the ocular globes, and occluding each nasal opening and testing air flow through the nares with a glass slide or cotton ball. With a nasal tumor, there will often be partial to complete obstruction of air flow depending on the size and location of the growing tumor.

Baseline diagnostics include blood work to rule out other conditions, fine-needle aspiration of regional lymph nodes with cytologic examination, skull radiographs (lateral and open mouth ventral dorsal) and biopsy with histologic examination.

When the nasal cavity is biopsied, it bleeds-a lot! The bleeding is usually self-limiting, but it's smart to warn the owner. Ice can be applied to the nasal cavity externally during recovery, or epinephrine can be instilled into the nasal cavity to promote vasoconstriction.

If the owners can afford it, a CT scan provides superior imaging that allows for tumor staging. If an owner is considering radiation therapy, a CT scan is strongly recommended beforehand.

“What if I did nothing?”

Pet owners will often ask this question, which is very difficult to answer, says Fan. A 2006 retrospective case series looked at 139 dogs with nasal carcinoma that were not treated.1 They found that there was a three-month average survival rate with the longest being over three years, and survival rate was dependent on the owner's perception of quality of life. If the client elects not to treat the cancer, Fan advises that you inform the client of the pain associated with this disease and advocate to start pain management.

Reference

1. Rassnick KM, Goldkamp CE, Erb HN, et al. Evaluation of factors associated with survival in dogs with untreated nasal carcinomas: 139 cases (1993-2003). J Am Vet Med Assoc 229(3):401-406.

Treatment. Controlling cancer pain and shrinking the tumor with radiation are the mainstays of nasal cavity neoplasia treatment. Surgery and chemotherapy may play a role as well.

Pain control. Nasal neoplasia is a very painful disease. Analgesia with nonsteroidal anti-inflammatory drugs, tramadol or opioids is a cornerstone to all treatment, says Fan.

Radiation. Nasal neoplasms are managed locally; distant metastasis is rare, says Fan. Thus, radiation therapy is the gold standard treatment of nasal cavity neoplasms in both dogs and cats.

In dogs, Fan says, the median survival time for dogs and cats after treatment with curative intent radiation therapy is one year with a reasonable quality of life. Carcinoma survival time with treatment is six to 12 months, while sarcoma is 12 to 18 months. In cats, nasal lymphoma is highly responsive to radiation, with survival rates greater than two years, carcinoma and sarcoma 12 to 18 months, say Fan.

It's important to let clients know that patients receiving radiation treatment will not be completely free of clinical signs. Fan says they often have persistent, but less severe clinical signs of rhinitis and sneezing. These signs are typically not enough to negatively impact quality of life, and the important point to stress is that the animal is no longer in pain.

The downsides to radiation therapy are that the treatment is expensive, ranging anywhere from $5,000 to $8,000; there are limits to the total cumulative dose that can be given without permanently damaging normal tissues within the radiation field; and there are chances for self-limiting adverse side effects.

Side effects are divided into acute and late. Fan recommends educating clients that acute side effects affect quickly dividing cells, are expected to heal after four weeks and are transient in nature. These include mucositis and ulceration in the mouth, rhinitis, dry eye, corneal ulceration, solar dermatitis, moist desquamation and alopecia. 

Late side effects affect slowly dividing cells and limit the amount of radiation that can be delivered, says Fan. These include retinal damage, bone necrosis, nervous tissue injury and potentially secondary neoplasia. Late side effects are permanent and considered undesirable.

Chemotherapy. A small study showed 50% to 100% reduction in nasal neoplasm in response to treatment with carboplatin, doxorubicin and piroxicam.4 Toceranib (Palladia-Zoetis) is a drug that has been shown to have activity against anal sac and thyroid carcinomas.5 Interestingly, in a pilot study, one out of seven dogs with nasal carcinoma had a complete response to Palladia.5

Surgery. In a 2005 retrospective study, when performed after radiation therapy, exteneration of the nasal cavity was supported by increased survival rates.6 Fan says surgery is generally contraindicated in fields that have been previously radiated with high cumulative doses, as increased complications are noted postoperatively.6

References

1. Gill VL, Bergman PJ, Baer KE, et al. Use of imiquimod 5% cream (Aldara) in cats with multicentric squamous cell carcinoma in situ: 12 cases (2002-2005). Vet Comp Oncol 2008;6(1):55-64.

2. Peters-Kennedy J, Scott DW, Miller WH Jr. Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topicalimiquimod 5% cream. J Feline Med Surg 2008;10(6):593-599.

3. Henry CJ, Brewer WG Jr, Tyler JW, et al. Survival in dogs with nasal adenocarcinoma: 64 cases (1981-1995). J Vet Intern Med 1998;12(6):436-469.

4. Langova V, Mutsaers AJ, Phillips B, et al. Treatment of eight dogs with nasal tumours with alternating doses of doxorubicin and carboplatin in conjunction with oral piroxicam. Aust Vet J 2004;82(11):676-680.

5. London C, Mathie T, Stingle N, et al. Preliminary evidence for biologic activity of toceranib phosphate (Palladia) in solid tumours. Vet Comp Oncol 2012;10(3):194-205.

6. Adams WM, Bjorling DE, McAnulty WM, et al. Outcome of accelerated radiotherapy alone or accelerated radiotherapy followed by exenteration of the nasal cavity in dogs with intranasal neoplasia: 53 cases (1990-2002). J Am Vet Med Assoc 2005;227(6):936-941.