While there is no gold standard to assess pain in patients, “veterinary medicine may under appreciate and/or poorly detect it in companion animals with cancer,” Dr. Philip Bergman told an audience at the American College of Veterinary Internal Medicine Forum in Nashville June 7.
Bergman, one of the nation’s premier veterinary oncologists and VCA Antech, Inc. director of clinical studies, said, in a presentation entitled, “Gaining on Pain: An Oncologist’s Approach”: “Thankfully, investigations into the mechanisms of companion-animal cancer pain have begun within the past 10 years and are now beginning to appear in veterinary literature, but far more investigations are desperately needed. Until then, we are forced to extrapolate information from the human side, which may or may not fully translate into our patients.”
A recent PubMed search of “human cancer pain,” he said, turned up 67,000 citations, but a similar check on companion animals revealed fewer than 300, with many of those minimally associated with animal cancer pain studies.
With the backdrop of these human studies, Bergman cited five potential reasons for poor detection of cancer in pets:
(1) Veterinarians may focus more on the treatment than the pain (and forget that some treatments temporarily cause pain in and of themselves).
(2) They may poorly assess pain, and dogs/cats possess and innate ability to mask pain and disease.
(3) They may poorly teach clients and staff how to determine pain in their pets.
(4) They may have a variable understanding of possible drugs and other pain-relief techniques.
(5) They may have a limited grasp that many different tumors are significantly associated with pain.
Years of experience have taught Bergman the importance of listening to the owner and asking open-ended questions relating to pain-associated behaviors at home. “Remember, they see the patient around the clock and can read changes in its body language and behavior. We need their input when establishing a course of treatment. The more information they can provide, the better.”
His treatment guidelines, dictated by minimizing the patient’s pain and maximizing its quality of life in the process, include:
(1) Incorporate a pain evaluation into the standard physical examination.
(2) Determine and deliver the best treatment(s), often recognizing this requires a multimodal approach.
(3) Repeat and revert back to owner questions and communication, maintaining a fluid approach of patient care.
Tumor pain varies widely by type, he said, Those most commonly associated with pain in order of descending severity are primary and metastatic bone tumors, inflammatory mammary carcinoma, oropharyngeal or nasal tumors (especially with bony destruction), ulcerative and/or invasive skin tumors and a wide mix of others.
Pain signs in veterinary cancer patients, Bergman noted, are decreased appetite and/or activity, changes in attitude, increased hiding, increased respirations or overt panting, poor self-grooming, aversion to touching and/or palpation of the affected area, self-trauma, changes in facial and/or ear expressions and changes in urination and/or defecation.
“Each patient’s pain tolerance and reflection of pain is different,” he added, “but all require the same level of care. Controlling pain is important for physiologic and ethical reasons.
“It is important to note that vocalizations are seen rarely in response to chronic pain in dogs and cats. Hence we have a duty to inform our clients of this since this is not intuitive for the lay public. Cats may have changes in their meows or may hiss or purr when experiencing cancer-associated pain. Dogs may display grunting and/or whining.”
There are numerous options when treating pets for cancer. Bergman said that whenever possible focus on the tumor causing the pain. Surgical removal of the neoplasm is the quickest and least expensive approach. “When local treatments are indicated,” he said, “and surgery is not an option due to logistical, financial and/or emotional constraints, radiation is often a next best choice.”
Bergman cited an “incredibly helpful” 1986 World Health Organization “pain ladder” that details pain management at three levels. “But with advent of new analgesic treatments, four-and five-tiered ladders are being used more frequently in the treatment of human cancer-associated pain,” he said.
While human medicine is far ahead of its veterinary counterpart in assessing pain, Bergman challenged his veterinary counterparts, “We must do better. We owe it to the animals we treat and their committed owners.”
One of the nation’s most noted veterinary pain-management experts, Dr. James Gaynor, of Frisco, Colo., who attended Bergman’s presentation and who has collaborated with the oncologist for years, adds, “Both acute and chronic pain can elicit a stress response which affects virtually every organ system in the body. When left unchecked, chronic pain can decrease the rate of healing, impair the immune system and decrease cardiac and pulmonary function, to name a few.”
The most common initial treatment for chronic pain in dogs, says Gaynor, is the prescribing and administering of nonsteroidal anti-inflammatory drugs (NSAID), of which six are approved for use in dogs. Aspirin is a non-approved NSAID and in general should be avoided in dogs for pain-relieving purposes, he emphasizes.
Regenerative stem-cell therapy is quickly becoming a measuring stick for medical therapy to control arthritis-related pain, Gaynor added. It uses dogs’ own adult stem cells to help themselves. “The cells have incredible pain-relieving attributes with no side effects,” explained Gaynor.