The Dog Cancer Survival Guide (105 page)

As I noted above, median survival times for dogs with visceral or heart HSA are only one to four months with surgery alone. Post-operative chemotherapy increases that survival time to six months, which is why I recommend chemotherapy for all dogs with HSA of the internal organs, the heart, subcutis or muscle HSA.

(I do
not
recommend chemotherapy as a standalone treatment, because survival times are very poor without surgery first.)

Doxorubicin is the most (and possibly the only) effective chemotherapy drug for HSA. Protocols vary and are evolving, so, there is no one best protocol to recommend. As you’ll read in the section on chemotherapy, doxorubicin is a potent vesicant, which causes severe damage to skin and other tissues if it gets outside the vein. It must be handled very carefully and I strongly recommend you have an oncologist handle these treatments.

Most published protocols consist of five or six treatments, but I recommend a more extensive chemotherapy schedule. Chemotherapy treatments should be a regular event for the rest of your dog’s life. This aggressive disease requires aggressive treatments, and in my experience dogs can live a good life while on chemotherapy. Of course, I recommend periodic imaging tests to see if the disease is progressing internally and evaluate whether the chemotherapy is having the desired effect. We typically stop using doxorubicin after six treatments due to its potentially toxic effects on the heart; past this point, consider transitioning to a metronomic protocol (see below).

When your dog has a ruptured spleen or hemoabdomen (free blood in the abdomen) at the time of diagnosis, I also consider adding intracavity chemotherapy to the protocol. You’ll remember that HSA is capable of spreading throughout the abdomen, when released into the cavity by a rupture. In this strategy, we chase that transabdominal seeding by depositing chemotherapy drugs directly into the abdominal or chest cavities, rather than into a vein and the blood circulation. Doxorubicin must be injected directly into the vein to avoid tissue damage, so it cannot be used for this technique, but carboplatin or mitoxantrone may be used. The drugs are still absorbed and processed by the body, so side effects are similar to traditional IV chemotherapy. Since doxorubicin is the standard of care, I alternate IV doxorubicin with intracavity chemotherapy. It is unclear as of this writing whether this technique extends survival times; I only offer it as a possibility for inclusion in your treatment plan.

As with visceral HSA, the primary treatment for dogs with skin and subdermal HSA is surgery. The goal is to remove the tumor completely with wide (two to three centimeter) margins, if possible. A recent study has shown that aggressive surgery and clean surgical margins are related to long survival times – over four years tumor-free for dogs with subcutaneous HSA treated with surgery and doxorubicin (with or without radiation).

When the tumor location forces the surgeon to use narrow margins or the biopsy shows dirty surgical margins, radiation may be needed to prevent recurrence at the surgical incision.

When the tumor is non-resectable, palliative radiation may help to reduce it, and stereotactic radiosurgery can also be considered.

I recommend chemotherapy for skin HSA, based on the stage of the cancer. Less than 30% of stage I HSA cases metastasize, so when the surgery achieves clean margins or radiation was done after surgery, the HSA may be cured. In these cases, I recommend rigorous, routine checks every three to four months without fail to check for new masses and for metastasis. In addition, I may recommend chemotherapy on a case-by-case basis for stage I dogs whose biopsies show an increased risk of metastasis.

Stage II and III HSA skin tumors, on the other hand, are highly metastatic, similar to HSA of the internal organs. Most dogs with subdermal HSA ultimately succumb to metastasis, so I recommend the chemotherapy protocols discussed for the internal organs, above.

An exciting new approach to chemotherapy is called metronomic chemotherapy, which abandons the traditional technique (higher doses – the maximum tolerated dose – with longer breaks in between) in favor of low doses of oral chemotherapy agents, given daily or with few breaks. This therapy is technically not aimed at killing cancer cells – instead, it targets their blood supply and metastasis routes by inhibiting angiogenesis, or the growth of new blood vessels.

Because HSA is a tumor of the lining of the blood vessels, this approach is a logical route to try. Not only does it target and destroy endothelial cells in the blood vessels (the very cells involved in this cancer and also the vessels that carry blood and oxygen to these tumors), but also seems to enhance the immune system’s response to tumors. A recent study showed that a metronomic approach is comparable to conventional chemotherapy, so it merits consideration, especially since the new class of drugs, called tyrosine kinase inhibitors (Palladia, for example), have anti-angiogenic effects. It is not yet clear whether metronomic chemotherapy will result in longer survival times for HSA patients, and there is still much to be learned. Nevertheless, I like the minimal side effects of these protocols and the fact that the owner can usually manage them at home. There may also be value to combining metronomic protocols with traditional doxorubicin, for example. Protocols are constantly evolving, and even though close supervision and routine visits to the vet are still necessary, I strongly recommend you consider metronomic chemotherapy with your vet or oncologist.

There is a lot of interesting research happening in the field of immunotherapy applied to HSA, however, the protocols being worked out are not yet available commercially. It is worth asking your vet or oncologist about this approach, as medicine is constantly evolving. Newer approaches are needed and are being investigated.

“Even though at first you may think the situation is insurmountable, please do not throw in the towel. You can, through help and guidance and understanding, help you and your friend through these tough times. It’s normal to be confused, sad and angry at the same time. You need information from knowledgeable people. You need to become informed on everything dealing with the problem. You can then base your decision and plan of action based on what is best for your friend. The treatment is for them, so don’t give up; do what is possible for them and for you.”

-
Jon Marshall, Norman, Oklahoma

While a diagnosis of HSA is very discouraging, there are treatments available that can extend your dog’s life. I urge you to consider all of the options carefully and make a well-informed decision. It is important to remember that treated dogs can live longer and live well.

T
ransitional cell carcinoma is a cancer of the urinary tract. Tumors are most often found in the bladder and they can also be found in the urethra, ureters and prostate gland. Transitional cell carcinoma is commonly referred to by its initials, TCC.

Bladder TCC moves very fast, spreading locally through the urinary tract and distantly to areas such as the lymph nodes, lung, liver and bone. About 15% of all afflicted dogs already have metastasis at the time of diagnosis, and another 50% will develop metastasis as the disease progresses.

Due to the complicated nature of the urinary tract, TCC is rarely curable. Although surgeries can debulk (reduce the size) of tumors, it is next to impossible to achieve complete removal. For this reason, surgery is considered palliative, and following it up with chemotherapy and Cox-2-inhibitor therapies is the standard of care. Dogs treated with surgery alone live three to four months; dogs treated with piroxicam alone live six to seven months; median survival times increase to one year when surgery and piroxicam are combined with the chemotherapy drug mitoxantrone.

While curing TCC is not likely, it is considered a very treatable cancer. Combining therapies can both extend life and make dogs much more comfortable.

TCC is a cancer of the urinary system, a system made up of several organs working together to remove metabolic wastes from the blood and flush them out of the body. The upper portion of the system consists of the two kidneys (one on each side of the body). The kidneys have several important bodily functions, not the least of which is filtering the blood for elimination of toxins and wastes. These bean-shaped organs create the fluid we call urine, which flows down to the lower urinary system through the ureters (tubes) into the bladder. The bladder is a hollow bag, which expands as it collects the urine. When your dog urinates, the bladder releases the urine through the urethra, a tube that traverses the genital area until it reaches the exterior. The prostate gland surrounds the urethra in male dogs and empties its fluids into the urethra through tiny ducts, or tubes.