The Dog Cancer Survival Guide (115 page)

Chemotherapy is typically not effective for brain tumors because of the physiological phenomena called the blood-brain barrier (BBB). Brain tissue can be damaged by coming into direct contact with blood, so there are some inherent protections built into the brain’s structures to keep it from the blood supply. This barrier is semi-permeable: some materials can cross, while others can’t. Most chemotherapy drugs cannot cross this barrier, but others can, Including oral Lomustine and IV carmustine. These drugs seem to be the most effective therapies for gliomas and lymphoma (that involve the central nervous system). Oral hydoxyurea can also cross the BBB, which is effective for meningiomas. The median survival time for chemotherapy, as a standalone treatment, is seven months for dogs with all tumor types.

There are two state-of-the-art surgical techniques that may be of interest to some owners, because they allow for more complete tumor removal, crucial to delayed recurrence and longer survival times.

The first technique removes the tumor using endoscopy. This minimally invasive technique helps the surgeon to insert a camera into the brain, to see the tumor and make a more complete removal. There are minimal surgical complications with this technique, and in a study of thirty-three dogs, the results were notable. Dogs with meningiomas in the forebrain had a median survival time of 5.8 years, while dogs with meningioma in the caudal (back) area of the brain, in the brainstem or cerebellum, had median survival times of two years. Dogs with other types of tumors had a shorter survival time of six months. Not all neurosurgeons perform this specialized technique, but it may be worth inquiring.

The second cutting-edge technique to consider is the use of an ultrasonic aspirator. This advanced surgical device uses ultrasonic vibration to powerfully and precisely remove tumors. In a study on dogs with meningiomas who received this surgery, the median survival time was about forty- two months, or three and a half years, depending upon the subtype of the tumor.

Seizures are common for dogs with brain tumors, and should be managed as part of your dog’s care. Cluster seizures – two or more seizures happening in a short period of time – require hospitalization and injectable anti-convulsants. If brain swelling or herniation is suspected, a medication called mannitol is administered via injection, and oral steroids such as prednisone, are given, to reduce the swelling. You may need to continue these at home until instructed to taper off.

“In my line of work, I speak with dog lovers each and every day. Many of them have been through cancer with a dog or are facing that journey currently. There are a few things I would share with anyone watching their beloved pet struggle with cancer or any other disease for that matter: take every moment to be with your pet because nothing means more to them than your presence. Do the things that you can, and don’t obsess over what you cannot. So often it is the very little things like a ten minute massage or hand feeding your dog or carrying them outside and standing over them in the cold night air or a meal you made yourself that really matter so much more than expensive treatments or heroic efforts. If and when the time comes when a difficult decision must be made, be thankful for the mercy that we as guardians can provide our pets.”

-
Lola Michelin, Shoreline, Washington

If your dog is having seizures more than every six to eight weeks, oral anti-convulsants you can administer at home will likely be prescribed. A consultation with a neurologist will be helpful, also.

Seizure management is not just a palliative measure; it can also extend life. When used alone, steroids can extend life by weeks or months, and steroids combined with anti-convulsants can extend life from two to four months.

Brain tumors are a devastating cancer to deal with, and there are treatment options that can be used to control the tumor, significantly extending life and making your dog more comfortable. Oral medications are often palliative, but may also help.

P
erianal and anal sac tumors develop in the glands near and around the anus, just under the tail. Some tumors, called adenomas, are completely benign and do not spread, while others, called adenocarcinomas, are malignant. Perianal sac adenocarcinomas grow quickly; anal sac adenocarcinomas both grow quickly and are more likely to spread – more than 50% of afflicted dogs already have metastasis at the time of diagnosis.

Adenomas are related to testosterone levels and often shrink on their own after an adult male dog is neutered. They can also be surgically removed. Adenocarcinomas require more aggressive surgery, because regrowth is common. Some may require a multi-modal approach combining surgery, chemotherapy and radiation in order to extend survival times and improve quality of life.

When you need to look up the definition of a word or phrase, find it listed in
Chapter 5
, which begins on
page 46
.

The prognosis for these tumors varies widely depending upon the type of tumor and its own particular behavioral patterns.

Perianal adenomas are also known as hepatoid tumors and circumanal tumors, perianal adenocarcinomas as sebaceous adenocarcinomas, and anal sac adenocarcinoma as apocrine gland adenocarcinoma.

Any owner knows how dogs greet each other – by sniffing each other’s rear. While this seems odd to us, it makes anatomical sense: dogs literally express themselves in this area. Their distinctive smells are not from the feces, alone, they’re also coming from the anal sacs, two scent glands located on either side of the anus. These glands store secretions from apocrine (sweat) glands and sebaceous glands. Sebaceous glands secrete sebum, an oily, waxy substance that lubricates the skin and hair. They feed the anal sacs and surround the rest of the anus. These glands make it possible for the dog to defecate easily, and also provide a wealth of aromatic information for other dogs.

When the dog defecates, the anal glands secrete their stored sweat and oil, leaving that distinctive foul-smelling (to us) scent on the feces. Cancers that develop in these glands are called anal sac adenocarcinomas (ASACs). These account for 15-20% of all perianal tumors and are the most aggressive. Because they specifically develop in the apocrine glands, or sweat glands, they are sometimes known as apocrine adenocarcinoma or apocrine gland anal sac adenocarcinomas (AGASACAs).

The many sebaceous glands in the anal region can also develop cancer. When testosterone levels elevate, these glands tend to enlarge and become noticeable. Benign tumors, called perianal adenomas, are very common in adult male dogs that are sexually intact or neutered late in life. Spayed females can also develop these tumors; this seems to be caused by elevated testosterone levels, which can happen with adrenal tumors and other testosterone-secreting tumors.

While most perianal tumors are benign, a few are malignant. When malignancies arise in the sebaceous glands of the anus, they’re called perianal adenocarcinoma, and the role of testosterone in their development is less clear. They do occur most often in intact male dogs, and they also occur in neutered males and both intact and spayed females.