Nasal passage cancer generally develops very insidiously in older pets. It is rare in cats and not common in dogs. It composes about 1 percent of feline tumors and up to 2.5 percent of canine tumors. Long-nosed breeds (dolichocephalic) and senior dogs are at higher risk. Clinical Signs Of Nasal Passage The early signs of nasal cancer in dogs or cats are: Unilateral nasal and/or ocular discharge Epistaxis Stridor Loss of smell Loose teeth Sometimes pawing at the face Late-stage signs may include a facial deformity along the dorsal aspect of the maxillary bones or over the paranasal and frontal sinuses. Some cases develop a raised or pitting facial bone deformity. Some cases may exhibit a firm or soft focal, raised mass protruding around or between the eyes. Some cases may have a palatine deformity from the softening and bowing out of the hard palate due to demineralization of the palatine bone and growth of the mass. In every case of facial deformity, there is bone lysis and tumor invasion at that site. If the lesions extend into the brain, seizures and behavior changes are often exhibited. A complication of nasal cancer is the over production of mucus. It collects and clogs the nasal passages and sinuses. How To Prepare The Pet Owner The stridor and mess from sneezing out phlegm along with the vivid color of blood during episodes of epistaxis cause great distress for pet owners. Most animals with nasal cancer exhibit sporadic signs in the early stages, then show progression over a period of about three months before diagnosis. Initially, the clinical signs fit the assumption that the pet has one of a variety of nasal conditions. Most clinicians would suspect or that a foreign body is lodged in the nasal passages. A search for the offending material finds nothing. If the nasal passages are cultured, pathogens are often found and identified on culture and sensitivity reports. So, the diagnosis of rhinitis may suffice for a time. Some elder pets have oronasal fistulas from infected or extracted teeth to complicate matters. If the symptoms persist, the working diagnosis is often presumed to be either a foreign body that remains wedged in the upper turbinates or chronic rhinitis. In some case histories, the nasal passages were explored several times without locating a foreign body yet no biopsy or culture was taken. Since the problem is presumed to be either infectious or allergic, the patient is placed on symptomatic treatment with antibiotics, steroids and antihistamines or nose drops for topical therapy. The patient often gets relief from symptoms. This is why most nasal cancers go undetected for three months and why some cases may go undetected as long as six months in dogs and up to two years in cats. Diagnosis Of Nasal Cancer The best radiographs for visualizing the nasal cavity are taken under general anesthesia with the X-ray film placed into the open mouth for an intranasal view. Teach your X-ray technicians to use the positions from a good radiology text for open-mouth studies of the nasal cavity. Place the X-ray film inside the mouth. Place one corner extending as far back toward the tonsils as possible and take a DV image. This provides the best exposure of the nasal passages. Intra-oral radiography is best accomplished with high quality non-screen film; we use mammography film. The A-P skyline position for the best view of the frontal sinuses of the skull is also very important to complete a full skull series. Look for space occupying or lytic disease in the nasal passages or sinuses. Look for an asymmetrical density or lysis or interruption of the fine scroll pattern of the nasal turbinates, a break in the fine lines of the nasal septum or a density in one of the frontal sinuses. Too many cases of nasal cancer are initially missed on the first X-ray series because of poor visualization. Magnetic resonance imaging or computerized tomography scans of the nasal passages and paranasal sinuses have become the gold standard for imaging nasal tumors. Localization of the lesion is necessary for treatment planning. A small number of patients may have lymphadenopathy. It is important to discuss the usefulness of MRI or CT scan in this setting with the pet owner. CT technology is used for computerized treatment planning for radiation therapy patients. So, if the patient will be receiving radiation therapy, it may save time and money to order a CT scan from the start. Since general anesthesia is needed for these studies, it may be the best opportunity to also request tissue samples for definitive diagnosis. Some imaging services are set up to accommodate biopsy procedures and some are not. I prefer to refer cases to facilities that will do a biopsy. Perform A Biopsy If a geriatric patient is going to be anesthetized for X-rays, a biopsy should be done at the same time. The radiographs will suggest the best area to sample. Various instruments can be used but all require precautions to avoid penetrating the ethmoid plate. Rhinoscopy with direct biopsy of the abnormal tissues is most direct. A long true-cut biopsy needle, a plastic cannula or biopsy forceps is passed through the nostril into the nasal cavity and thrust into the suspected lesion to harvest a sample for histopathology. For safety, always measure the distance between the tip of the nose to the area just in front of the ethmoid (cribriform) plate. This should be just in front of the medial canthus. Mark the biopsy instrument with tape or ink. In cases with nasal bone deformity or a bulge over a sinus, one can generally pass an FNA needle directly through the skin and softened bone into the lesion and aspirate a sample for cytology. One can also insert a true cut instrument through the bulging defect and into the sinus to get a sample for histopathology. In most cases, the harvested material is gelatinous and difficult to distinguish from phlegm. Expect bleeding and if necessary, use cotton soaked in epinephrine to pack the nostrils. It may be necessary to keep the patient under anesthesia or quiet with sedation until bleeding is controlled. Pathology Pathology reports identify most canine nasal tumors as carcinomas. Most of them are respiratory adenocarcinoma followed by squamous cell carcinoma and a few miscellaneous or undifferentiated carcinomas. About one third of nasal cavity neoplasia in dogs are sarcomas, with fibrosarcoma being most common followed by chondrosarcoma, osteosarcoma, lymphoma, and then other miscellaneous and undifferentiated sarcomas. North Carolina State University summarized 320 cases of nasal tumors in cats, finding that 60 percent were carcinomas, 18 percent sarcomas and 12 percent lymphoma. There is no correlation with grade and survival. However, some tumors may have a low mitotic rate or a slower rate of growth or a less aggressive biological behavior than others, such as low-grade chondrosarcoma. Treatment Surgery for dogs with nasal cancer was routinely performed until data showed that rhinotomy (opening the nasal passages and scooping tumor out) was a negative factor for survival time. However, rhinotomy followed by orthovoltage radiation therapy yielded the longest survival times but rhinotomy was not necessary if the pet was to receive cobalt radiation therapy. This information and the poor survival data made treating nasal tumors confusing and frustrating. Today the norm is to avoid surgical rhinotomy. However, if pet owners are interested in radiation therapy, they should be referred for imaging studies to locate the extent of disease. Then refer them to a radiation oncologist for consultation regarding the risk-benefit ratio and an honest survival time discussion based on the tumor type and the individual pet’s stage of disease. The owner needs to reconcile his psychological, emotional, financial and ethical considerations regarding treatment for the pet. Most facilities use cobalt radiation therapy and CT scan technology for treatment planning. Some facilities treat pets with linear accelerators. There may be no difference in the survival times with either machine, but side effects may be less severe in animals treated with the higher energy linear accelerators. Of all nasal passage tumors, nasal lymphomas respond the best to radiation therapy as well as to chemotherapy. Most oncologists recommend systemic chemotherapy in addition to radiation therapy for nasal lymphoma because lymphoma is considered a systemic disease rather than a focal disease. This is especially true in cats. Drugs that enhance the effect of radiation (radiation sensitizers) such as mitoxantrone or carboplatin (some use low dose cisplatin) have been used. However, the advantage for survival is not yet firmly established. I think it makes sense to use systemic chemotherapy because it may enhance the radiation’s effects and also addresses the metastatic potential. This is important because 10 percent of patients present with lymph node metastases and 40 percent will go on to metastasize. Local recurrence and metastases are the main reasons for death of pets treated for nasal cavity cancer. So, there is a need to keep searching for better ways to enhance local control and control of metastatic disease. The side effects of radiation therapy for nasal cancer are quiet severe, especially if the tumor approaches the ethmoid plate or invades the orbit. Patients experience radiation-induced oral mucositis, chealitis and conjunctivitis. The client must be informed and prepared for the responsibilities of home care during and following treatments. Pet owners must also be told to expect chronic nasal discharge following treatment. The normal delicate tissue of the nasal turbinates will never again function properly due to permanent injury from the radiation therapy. Cataracts and blindness following radiation therapy will occur if the orbit is invaded by the cancer and if the eyes are included in the treatment field. Chemotherapy is often elected as a palliative and less aggressive therapy, especially in advanced cases that have poor prognoses. Many oncologists offer medical management for clients who decline conventional radiation therapy for their pets. I like to use carboplatin rotating with mitoxantrone every 21 to 30 days for most adenocarcinomas and carboplatin rotating with adriamycin for sarcomas. I also use long-term doxycylcine as my antibiotic of choice and an NSAID such as piroxicam, deracoxib or meloxicam for pain control and their anti-angiogenesis action. Clinical improvement is often reported for pets on chemotherapy with reduction of epistaxis, sneezing, snorting, stridor, nasal discharge and pain relief. Patients do not seem to have extended life spans with chemotherapy but many seem clinically improved for a variable amount of time. Prognosis The prognosis is generally grave to very poor. Untreated dogs and cats usually die within two to seven months of diagnosis. If rhinotomy is the only treatment, survival is actually shorter. In selected cases that receive radiation therapy (plus or minus adjuvant therapy), survival can be raised to a range of eight to 25 months. The one-year treatment survival may be 40 percent and can go up to 80 percent in select cases. Half of the one-year survivors die in the second year. Palliative chemotherapy may improve clinical signs for a time but does not seem to extend survival. If you are trying to select a good case for radiation therapy, sarcomas do better than carcinomas and respiratory adenocarcinomas do better than other carcinomas. Tumor size and location are also factors. Localized lesions in the rostral to middle part of the nasal passage do better; most are in the caudal two-thirds of the nasal passage. Lymphomas respond the best and low-grade chondrosarcomas have the potential to survive the longest. Radiation therapy for nasal passage cancer is a difficult process for the patient and caregivers. The risk-benefit ratio must be weighed carefully in each case. Therefore, during consultation with the pet owner, it may be difficult to recommend conventional therapy over palliative therapy, especially for advanced cases due to the overall poor prognosis.
