The Dog Cancer Survival Guide (109 page)

Radiation therapy can, in some cases, dramatically improve the life expectancy of a dog with an oral tumor. As we discussed in
Chapter 11
, radiation has several side effects, some of which occur immediately and some, later. Early side effects include inflammation of the gums, hair loss, skin burning, difficulty eating and eye issues (such as conjunctivitis). Fewer than five percent of patients experience late-occurring side effects, such as an uncomfortable condition called dry eye, fistulas (holes between the nasal and/or oral cavities), bone damage (rarely), malignant bone tumors and, if the eyes were in the radiation field, cataracts. If you are near a CyberKnife or other radiosurgery device, it is well worth considering this type of conformational therapy, which can dramatically lessen the side effects of radiation.

While chemotherapy is sometimes considered, oral cancer rarely metastasizes to distant locations, so it is not usually indicated. Of course, all dogs are considered on a case-by-case basis, and if spread is found (especially to local lymph nodes), chemotherapy is recommended.

There are a few specific considerations for each tumor type.

The goal of SCC treatments is local tumor control, and surgical excision is usually the most economical, the quickest and most curative surgery. When feasible, this is my first choice of treatment. Seventy to ninety percent of dogs with SCC survive for one year with these surgeries, and survival times as long as eleven to twenty-six months have been reported. Rostral tumors (in the front of the mouth), may even be cured. Clean margins on the post-surgical biopsy offer even more hope, because recurrence is much less likely. Surgeries of the lower jaw are also less likely to recur (10%) than upper jaw surgeries (30%). If your dog has a caudal SCC tumor in the back of the mouth, at the base of the tongue, or on the tonsils, the prognosis worsens because these tumors are more likely to spread. After surgery, additional radiation therapy may be necessary, and, often, chemotherapy.

Carcinomas, and SCC in particular, are sensitive to radiation, so it is worth considering. In general, radiation therapy is best for treating microscopic disease after surgery removes the visible or measurable tumor. Also, radiation can treat regional lymph nodes. If used as a stand-alone therapy for SCC, median survival times of twelve to sixteen months are reported. Combined with surgery, however, those survival times lengthen to thirty-six months. The most important factor in predicting how responsive a tumor will be to radiation is its size – the smaller the tumor, the more radiation helps.

The first choice of treatment for FSA tumors is surgical excision. Wide margins of at least two centimeters are necessary, if possible, to completely remove the tumor. Even with these wide margins, however, FSA may leave microscopic cells behind. Local recurrence occurs in about half of FSA cases and this is the usual cause of death. The median survival time is approximately one year with aggressive therapy of surgery or radiation therapy alone. Combined, the use of surgery and radiation improves survival times to eighteen months. The high likelihood of recurrence is both frustrating and upsetting, which is why I advocate for aggressive approaches to FSA.

For that tricky Hi-Low FSA, surgery rarely achieves clean margins, so radiation is highly recommended after surgery. In general, oral Hi-Low FSA tumors are not as sensitive to radiation, so using it as a standalone therapy is not recommended.

Even though benign dental tumors may not be malignancies, they can cause problems, and so surgery and radiation therapy are often recommended. They are usually well controlled with treatment, even when tumors are large. Over ninety percent of dogs are alive at one year, and the median survival time is two to five years.

Dental tumor surgery must be aggressive, because these tumors are likely to recur. For example, tumors that arise in the periodontal ligaments, the connective tissues that anchor teeth in their sockets, tend to recur. When such a tumor is found, the vet must remove not only the mass, but also the entire tooth, socket and ligament. If your dog has an acanthomatous ameloblastoma, aggressive, partial jaw removal with at least one centimeter margins is required and is usually curative.

Radiation therapy is useful for non-resectable dental tumors, incomplete resections and recurrent tumors. Acanthomatous ameloblastoma tumors are particularly sensitive to radiation, with 90% under control after treatment, especially smaller tumors of less than four centimeters. Larger tumors are more likely to recur, and radiation typically controls only about 30% of these tumors. It is worth noting that, while it is rare, three to twelve percent of dogs with acanthomatous ameloblastoma develop malignant tumors years later as a result of receiving radiation therapy.

If you decide against surgery, or if the tumor is non-resectable (for example, a tumor of the upper palate that crosses the midline), you might consider a course of palliative radiation. This decision will be based on how involved the tumor looks on the CT scan, not on the oral exam alone.

While chemotherapy can delay metastasis in many other cancers, metastatic rates in oral cancers are typically pretty low, so chemotherapy is usually not considered. The exception to this rule is SCC found at the back of the mouth, the base of the tongue or the tonsils. Tonsillar SCC has a metastatic rate of over 90% to the regional lymph nodes and 60 -70% to the lungs, so chemotherapy is recommended to help control this spread. The best protocols are still being worked out; consult with your oncologist about the latest research. Chemotherapy is recommended after local control has been attempted with surgery and/or radiation, and may even provide some local response in these cases.

The NSAID piroxicam may help to slow tumor progression, due to its anti-inflammatory and anti-cancer properties, especially for carcinomas, and specifically for SCC. It can also help reduce the pain and inflammation associated with tumors, especially bone invasion.

While we are not yet sure how exactly piroxicam works against cancer, there is speculation that its inhibition of an enzyme called cyclooxygenase (COX-2) is at work. This enzyme blocks angiogenesis and therefore tumor growth, and piroxicam has a 20% response rate when used alone to treat SCC. A second, small study used carboplatin chemotherapy in addition to piroxicam, which bumped the response rate to almost 60%. Unfortunately, the study sample was too small to say for certain that these are typical results.

In addition to this specific anti-cancer effect for SCC, piroxicam has been effective at delaying the recurrence of soft tissue sarcomas when it’s combined with chemotherapy. Metronomic protocols, which use low doses of oral chemotherapy to block new tumor blood vessel formation (rather than trying to kill cancer directly), show some promise, too. Since oral FSA is a type of soft tissue sarcoma, and with the recent arrival of the promising anti-angiogenic drug, Palladia, metronomic protocols may be an excellent alternative to post-surgical radiation therapy or as a palliative option for local tumor control.

Although aggressive surgeries may be required to control oral cancers, they are highly treatable, especially when detected early. Finding an experienced surgeon who can do an aggressive first surgery is my highest recommendation Most owners in my practice are satisfied with the outcome after surgery, radiation therapy and, less commonly, chemotherapy.

“This is one of the toughest things you will ever go through. Make sure you find the right vets, do your research, and double check your research. Not all vets are made the same. Be INVOLVED in your pets care. Research, research, research. Just like when a human goes to a doctor and you have to be your own advocate, you need to be your pet’s advocate too. Don’t be afraid to seek a specialist, don’t be afraid to ask for your pets records to go see a specialist, and don’t be afraid to seek a second opinion. Don’t be afraid to ask questions, and don’t be afraid to question anything that doesn’t feel right in your gut. Stay positive around your dog. That’s not to say, that you can’t go hide in your car by yourself and bawl your eyes out. For me, I hid in the shower and cried my heart out, but as soon as I came out I had to put on a happy face and bring out that positive energy for Daisy. Do what you can to help stimulate your dog. You may not be able to do the things you used to do, but maybe just going for a ride, playing a game of paddy cake or hide the cookie, or sitting at a field, by the water, at a park, and just watching the world go by together. That can make a world of difference to your pup and give them something to look forward to every day.”

-
Chris Shoulet, Bethesda, Maryland

N
asal tumors develop in several tissue types found in the nasal and sinus cavities in the head. They tend to be very invasive locally, spreading into the neighboring tissues and often showing extensive bone involvement at the time of diagnosis. Despite their local aggression, they are not likely to have metastasized at the time of diagnosis.

Nasal tumors are typically not cured with treatment, although life can be extended with radiation therapy and sometimes, surgery. Most afflicted dogs live for about one year with treatment, and some live as long as two and a half years, depending upon the tumor type. While there are unavoidable side effects to radiation (see
page 125
), dogs generally tolerate the treatments.

Nasal tumors start inside the nose or sinus cavity, the tumor type varying, depending upon the tissue in which they occur. The vast majority of nasal tumors are malignancies that arise in the inside lining of the sinuses, cartilage, bone or lymphoid tissues.

About two-thirds of nasal cancers are carcinomas, or cancers of the epithelial cells. The many types of epithelial cells create the lining of the organs and structures in the body. The most common cancers are adenocarcinomas (ACA), which occur in cells that secrete fluids. Overlapping, fish-scale-shaped squamous cells develop squamous cell carcinoma (SCC). There are also undifferentiated carcinomas, whose specific cell of origin has not been determined.