What Can Be Learned About Treating Cancer in Captive Apes?
For pet owners, receiving word that one’s beloved canine, feline, or animal companion of another species has cancer is one of the worst imaginable conversations that can be had with their veterinarian.
I’ve endured this conversation as pertains to my own dog Cardiff. Yet, I was part of Cardiff’s cancer diagnosis process from the get-go, as I suspected he had a stomach, intestinal, or other abdominal organ tumor based on his clinical signs of anorexia (decreased appetite), regurgitation (bringing up partially digested food post-consumption), and lethargy. I also assisted on the ultrasound discovery and surgical removal of the small intestinal mass and then personally delivered the news to myself upon receiving the histopathology (biopsy) report. Needless to say, Cardiff’s cancer diagnosis wasn’t surprising but I knew that next up was the life-altering plan for a 7-month-long chemotherapy course (University of Wisconsin-Madison Canine Lymphoma Protocol, or CHOP) and other treatments to provide him with the best possibility of beating the cancer and experiencing the quality of life I’ve set out to provide.
As November is National Pet Cancer Awareness Month, my petMD Daily Vet articles are going to have a cancer-specific theme. Although society is generally aware of the options for veterinary services available to our canine and feline companions, we often fail to consider similar needs for animals residing in zoos, wildlife centers, laboratories, on movie and television sets, and more.
I recently became aware of a cancer patient of a unique species, a gibbon (a type of ape), who was treated at the Veterinary Cancer Group (VCG) in Culver City, CA, where on a weekly basis I work with veterinary oncologists who provide chemotherapy and radiation treatments to pets.
Jarred Lyons, DVM, DACVR-RO is both a veterinary oncologist who specializes in radiation treatments for animals and is the author of Survivor: The Dog Days of Cancer. I’m constantly intrigued by his veterinary practice, which is exclusive to oncology. Dr. Lyons only sees dogs, cats, and other species with cancer at VCG and is a true expert in his field.
Dr. Lyons oversaw the radiation treatment for the gibbon, a 25-year-old female named Ricky, who was born in Australia but has been living in Santa Clarita, CA, for 20 years at the Gibbon Conservation Center.
I had the opportunity to interview Dr. Lyons about Ricky’s case and his role in the cancer treatment process.
Dr. Mahaney: What kind of cancer did Ricky have?
Dr. Lyons: Ricky had a soft tissue sarcoma.
*Soft tissue sarcoma is a malignant cancer of connective or other non-skin tissue; Ricky had it on her left ankle. Malignant cancers are more serious than benign tumors as they are locally invasive and more prone to spreading to other parts of the body from a primary location. Sarcomas can arise from many body tissues, including muscle, connective tissue (ligament, tendon, etc.), bone, or others.
Dr. M: Is it unusual for a primate like a gibbon to develop this type of cancer and did Ricky’s age play a factor in her cancer development?
Dr. L: It is very unusual for gibbons to develop cancer and in fact at the Gibbon Conservation Center this is the first gibbon they’ve ever had that developed cancer. Like people these days, older gibbons are at higher risk for developing cancer. Whether that [the development of cancer] has to do with environment, genetics, or food is still an unanswered question.
Dr. M: What kind of treatment did you provide to treat Ricky’s cancer (please mention definitive vs palliative radiation and Cyberknife if used)?
Dr. L: We ended up giving a hypofractionated radiation protocol with the intent of definitive therapy. We radiated with our Trilogy linear accelerator with 6 doses total and given on a 2 times a week schedule. Given the fact we could not anesthetize 18-22 times on a daily schedule, I elected to treat with a high dose of radiation that could be administered safely and that could have a more definitive effect.
*When providing radiation treatment, palliative and definitive are two of the options available to animals. Palliative radiation involves fewer treatments and is aimed at reducing tumor size and associated inflammation, thereby alleviating pain and improving the patient’s comfort and quality of life on a more short-term basis. Definitive radiation requires a larger number of treatments and also strives to reduce tumor size and tissue inflammation, yet the goal is to have a higher likelihood of a cure or a longer caner-free interval.
Animals are fully anesthetized for a short time, often only 15-30 minutes, for each treatment, which may affect the determination that definitive or palliative radiation is more appropriate for a particular patient. Additionally, the patient’s age, overall health, preexisting conditions (heart, lung, kidney, and liver abnormalities, and other diseases), and the owner’s financial capabilities also come into play.
Dr. M: How did Ricky recover from each radiation treatment?
Dr. L: Ricky recovered very well from anesthesia and her son, Dennis, joined her shortly after each treatment.
*A great video of Dennis (and another gibbon) enthusiastically latching onto Ricky post-treatment can be seen in this video: Watch: Baby Gibbon, Mom Cuddle After Cancer Treatment
Dr. M: Is there any risk for Ricky’s offspring in having contact with her post-radiation treatment?
Dr. L: No, Ricky’s offspring are at no risk for health concerns in having contact with her post-treatment.
Dr. M: What measures should be taken to ensure Ricky’s babies don’t cause any complications to her during her radiation-treatment and recovery process?
Dr. L: The radiation should not cause any significant dermal (skin and its associated tissues) side effects with the dose that was given so I would not expect any real complications during the recovery process.
*With an increased number of radiation treatments, there is a higher likelihood that the skin and other tissues in the area being radiated will incur side effects like inflammation, pain, and potential for secondary infection.
Dr. M: Did Ricky receive any other treatments besides radiation for her cancer (I know she had surgery as well)?
Dr. L: Yes, Ricky also had surgery to remove the tumor.
*Before undergoing radiation, Ricky had surgery to remove as much of the tumor as possible. Such is a common occurrence and surgery may be able to completely excise (cut out) the mass with clean margins, or the tumor may be incompletely excised leaving tumor cells behind and increasing the likelihood that recurrence will quickly occur. In Ricky’s case, the sarcoma regrew and radiation was deemed to be the best option to shrink the tumor and provide her with an ongoing good quality of life.
Dr. M: Is Ricky considered to be cured of her cancer post-radiation treatment?
Dr. L: The hope was to put Ricky in a stable disease state or decrease the size of the mass for a period of time. As far as being cured, there is always a chance [that her radiation treatments will provide a cure].
Dr. M: What are the steps being taken to monitor Ricky for cancer recurrence post-radiation treatment?
Dr. L: Dr. Martin, the on-site veterinarian at the Gibbon Conservation Center, is in charge of all further follow-ups and monitoring and is keeping a very close eye on Ricky.
*With any patient undergoing radiation, chemotherapy, or other cancer treatments it’s important that day-to-day behaviors (appetite, water consumption, bowel movement and urine production, activity, rest, etc.) are monitored in addition to frequent evaluation of the surgery site for recurrence of the tumor and of the whole body for development of new masses.
Dr. M: Will/can Ricky have radiation treatment in the future if her cancer recurs?
Dr. L: Yes, Ricky is definitely a candidate for future radiation treatments [should her cancer recur].
Hopefully, Ricky will have many years without a recurrence of her soft tissue sarcoma or the development of any new areas of cancer. If you are interested in helping fund Ricky’s medical care, financial contributions can be made in her name to the Gibbon Conservation Center donation page.
Dr. Patrick Mahaney