The field of veterinary oncology has advanced greatly in the last several years, and there have been some exciting developments in this area. NEWStat asked some of the top veterinary oncologists around the country what they thought were the most interesting and noteworthy recent developments in animal cancer research, as well as some of the studies they are involved with.

GREGORY OGILVIE

Gregory K. Ogilvie, DVM, DACVIM (Internal Medicine, Oncology), DECVIM-CA (Oncology), is director of the Angel Care Cancer Center at California Veterinary Specialists, a clinical care and research facility.

“There are literally dozens of amazing advances in cancer therapy that have revolutionized the way we defeat this horrible disease,” Ogilvie said.

Cyberknife

This high-tech tool is only offered routinely by two radiation oncologists, but Ogilvie says the CyberKnife is very effective in treating animal tumors. Cyberknife is a precise, highly focused radiation delivery system.

“Not only does it provide extraordinary cancer control, it also does so in a much shorter time with much fewer treatments than regular radiation therapy,” Ogilvie said. “So it is way cool.”

According to Ogilvie, the Cyberknife combines two systems: a compact, lightweight linear accelerator mounted on a robotic arm that sends the radiation to the patient; and an image guidance system that tracks the tumors location within the body in real time, and directs the radiation to the precise location where it is needed. The guidance system uses the patients skeletal structure or implanted radio-opaque markers as a point of reference, continuously re-imaged throughout the entire treatment.

Tyrosine kinase inhibitors

Earlier this month, the U.S. Food and Drug Administration approved the first drug to treat cancer in dogs, Pfizer Animal Health’s Palladia. This drug, along with another, Kinavet, manufactured by AB Sciences in France, are tyrosine kinase inhibitors that kill tumor cells and cut off the blood supply to the tumor, similar to the human cancer drug, Glevec. All of the experts interviewed mentioned the importance of this new drug.

“Both drugs, Palladia and Kinavet are effective for the treatment of mast cell tumors however there is evidence to suggest that the application of this class of drugs is much broader,” Ogilvie said. “Work underway at places like Angel Care Cancer Center will reveal the true potential of these cancer therapies.”

Ogilvie also mentioned the following developments that Angel Care Center is involved with:

• Biodegradable polymer-based therapy: Chemotherapy drugs are encapsulated in biodegradable polymers, then injected into a tumor. As the polymers degrade, the drugs are slowly released into the tumor over 30 days.
• Artificial stifles and elbows: Cancer of the stifle or elbow has resulted in only one option is cure is the goal: Amputation. Elite surgeons and scientists around the world have been successfully developing artificial stifles and elbows to allow these patients to have one other option: limb sparing surgery with normal anatomical function thanks to the advances in biomechanical implants.
• Nutrition and cancer: Researchers at the CVS Angel Care Cancer Center and elsewhere continue to investigate the benefit docosahexaenoic acid for enhancing quality of life while increasing the curative potential of chemotherapy and radiation therapy. The potential value of this long chain polyunsaturated fatty acid of the n-3 series appears to be enhanced with a diet low in simple carbohydrates and n-6 fatty acids.
• Palladium/Lipoic Acid Complex: Years of research at the CVS Angel Cancer Center have resulted in the findings that a unique palladium/lipoic acid complex is not only able to enhance quality of life of the cancer patient but that it may also be able to improve survival of some cancer patients. Indeed, over 70% of clients in one study concluded that the coordinated compound enhanced overall performance in their pets with cancer. When dogs with osteosarcoma were compared to historical controls, an enhanced survival time was identified, initiating the need for a double blind, randomized, placebo controlled study to explore this observation.

LAUREL WILLIAMS

Laurel Williams, DVM, DACVIM (Oncology), is an associate professor in the department of Clinical Sciences at North Carolina State University’s College of Veterinary Medicine. Williams is involved with two studies on lymphoma, the most common hematopoietic tumor in both cats and dogs.

Williams’ cat study focuses on a novel treatment for cats with high-grade lymphoma confined to the abdominal cavity.

“Reports on conventional chemotherapy describe relatively low response rates, ranging from 30-65 percent, with remission durations of 6-10 months,” she says in the study summary. “Combining chemotherapy with other modalities may prove beneficial in improving remission rates and duration ... The goal of this pilot study, sponsored by the Winn Feline Foundation, is to evaluate normal tissue tolerance to the combined approach of chemotherapy followed by abdominal cavity radiation therapy and is the first step in evaluating this novel treatment approach.”

Her dog study is designed to identify whether cardiac problems in dogs with lymphoma are associated with toxicity from the use of chemotherapy drug doxorubicin.

“Recognition of cardiac changes and tumor-related decreased left ventricular systolic function would aid in distinguishing abnormalities associated with lymphoma from those secondary to doxorubicin administration, thereby enabling optimal delivery of therapy without unnecessary discontinuation of doxorubicin and with possible reduction in doxorubicin-related cardiotoxicity,” her study summary says.

KIM CRONIN

Kim Cronin, DVM, DACVIM (Oncology), is co-founder of the New England Veterinary Oncology Group (NEVOG).

Cronin’s group is involved in a study looking at a novel formulation of taxol for the treatment of mast cell tumors in dogs. The study is on the drug, Paclical, and is sponsored by the drug’s manufacturer, Oasmia. The Phase III study is looking at the efficacy of Paclical versus CCNU for dogs with measurable disease. She noted that NEVOG is involved in this study due to the fact that they are a member of the Animal Cancer Institute (ACI).

Bone marrow transplants

Cronin noted that North Carolina State University now offers bone marrow transplants for dogs with lymphoma. The process involves harvesting stem cells from the patient, so no donor is needed.

“Although right now this is an expensive process and patients need to go to North Carolina, it is felt that as the technology is streamlined that it may be possible to offer this type of a service at other oncology centers,” Cronin said.

She said that although the long-term survival rate has not been established yet, the expectation is that it will be better than chemotherapy.

Metronomic chemotherapy

One of the big topics in veterinary oncology, metronomic chemotherapy is considered to be anti-angiogenic rather than anti-neoplastic protocol, Cronin said. The process involves the use of continuous low doses of chemotherapy to arrest blood vessel development.

“Endothelial cells are more sensitive to low doses of chemotherapy compared to tumor cells,” Cronin said. “With low doses of chemotherapy it is not likely that there would be significant side effects associated with this type of therapy. The most commonly used protocols include a low dose of chemotherapy as well as a COX-2 inhibitor (NSAID). The COX-2 inhibitors themselves also have anti-angiogenic properties as well as immunomodulatory properties.”