The Dog Cancer Survival Guide (102 page)

The most common chemotherapy drugs are doxorubicin, carboplatin, and cisplatin, which you can read about in
Chapter 41
. The published protocols vary on which drugs to use, frequency and number of treatments and, unfortunately, there is no single best protocol I can recommend. Consulting with an experienced oncologist, who can look at your dog’s case and weigh the options, is your best bet. The best time to start chemotherapy is soon after surgery (ten to fourteen days) and before the likely metastasis is detectable.

Once metastasis has been detected, there are several ways to treat it. In addition to using surgery, there is additional chemotherapy, including aerosol chemotherapy, which delivers the drug via the inhaled breath, directly to the lungs, without being diluted in the bloodstream. Another option is metronomic chemotherapy: frequent and low doses of chemotherapy, which can help block angiogenesis (new blood vessel formation) and block or slow metastasis (see
page 137
). There has also been some success with immunotherapy (see below) and with a radioactive bone-seeking isotope, samarium, which literally seeks out the metastasis for targeted destruction.

There are some other treatments that you may want to consider for your dog with OSA. For example, a class of drugs called bisphosphonates, used in humans with osteoporosis to stop bone resorption (bone loss, which happens when cells called osteoclasts break down the bones), is now being used in human cancer patients with bone metastasis. When used in dogs with OSA, bisphosphonates stop bone resorption and may have a direct toxic effect on OSA cancer cells. Treatments are usually given via IV fluids, over a few hours and there is a low risk of kidney toxicity (the kidneys should be tested before each treatment). This treatment is still new; although we do not yet know how much time it buys, it may be worth inquiring. In addition to its possible antitumor benefits, I have found bisphosphonates helpful for reducing bone pain from the primary tumor when surgery is not elected or the tumor is inoperable.

Immunotherapy, which is the direct stimulation of the immune system to fight cancer cells, has also been shown to be helpful. Inhaling interleukin-2 liposomes, for example, has been shown to be both safe and effective in dogs with advanced lung metastasis. This aerosolized therapy stabilized and/or caused regression for their lung disease. Dogs also found it easy to take. Another immunotherapy, called L-MTP-PE, increased survival times to fifteen months, when combined with chemotherapy. While this option is exciting, unfortunately, it is not yet commercially available. Hopefully, this and other new immunotherapies will come on the market soon.

COX-2 inhibiting drugs such as NSAIDs (non-steroidal anti-inflammatory drugs) are being investigated as another approach to controlling metastasis in OSA. COX-2 is involved in inflammation and these drugs stop its mechanism and reduce inflammation. They also, however, seem to have an impact on angiogenesis, which means they slow or stop tumors from forming new blood vessels.

Oral pain medications may be needed when amputation is declined or when there is detectable metastasis, especially to the bone. NSAIDs can be helpful, though rarely sufficient by themselves; they pose an increased risk for negative gastrointestinal affects such as vomiting and stomach ulcers, also. When NSAIDs cannot be tolerated, prednisone can be used in anti-inflammatory doses. (Remember to never use prednisone, any other steroid, or any anti-inflammatory with NSAIDs, due to the risk of stomach ulceration.)

Additional pain medications that are useful are acetaminophen with codeine, Tramadol, sustained-release morphine, gabapentin and amantadine. Many of these drugs can be used in combinations for best effects: some of my patients are on four or more pain medications to control their pain.

Another good pain control option is a Fentanyl skin patch, which allows a continuous dose of pain medication to be absorbed through the skin. Because this patch needs to be changed by the vet every three to five days, you may find it too burdensome to use.

“I used the
Vent if You’re Bent
exercise daily! I kept a journal where I could put all my feelings and emotions down on paper as a way to release them. Some days I said the same things, others, I was mad or emotional about different aspects of this disease that had affected the whole family. I also used the
Cheat Day
on occasion, because, knowing he had osteosarcoma, and realizing that it is the most aggressive and hard to treat cancer, I felt that he shouldn’t be denied what he loved, however, I didn’t want to “feed” the cancer either. The
Message Massage
also helped him immensely. I could feel him relax under the pressure of the massage and soothing words.”

-
Jill Stout, Medford, Oregon

As always, dogs on pain medications of any kind should be closely monitored for side effects and signs of toxicity.

While a diagnosis of OSA may be very scary, it is not an immediate death sentence. There is a wide variety of options available depending upon the underlying health of your dog, the extent of the disease at diagnosis and your ability to commit to extensive treatments.

“It is beyond daunting when one first gets the news. Often there are some very hard decisions to make. One I had was - am I doing this for me or her? Especially with an amputation - will her life be as enjoyable? As much as I respect my Vet, he like many others does not have the knowledge and information to go beyond the traditional treatment. I am so happy I did my own research and found Dr. Dressler’s book. It is very empowering and gave me some of the direction I needed to move forward. I believe every Vet should have this book as a resource to offer people when they are faced with this life-changing news.”

-Keefer Irwin, Rochester, Vermont

H
emangiosarcoma is a cancer of the lining of the blood vessels, and it occurs more frequently in dogs than in any other species. Because blood vessels are everywhere, hemangiosarcoma can develop in any location. The most common site for a primary hemangiosarcoma tumor is the spleen, followed by the right atrium of the heart. Other primary locations include the skin, subcutis (a layer of tissue just under the skin), muscle tissue and liver. Hemangiosarcoma, also called angiosarcoma and malignant hemangioendothelioma, is often abbreviated as HSA.