Understanding and recognizing cancer pain in dogs and cats - Veterinary Medicine
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Understanding and recognizing cancer pain in dogs and cats
They may not speak, but our patients with cancer can still tell us they're in pain. Are we getting the message? With careful observation and good client communication, we can identify pain. And with an awareness of the cancers and procedures known to cause pain, we can offer preemptive pain control.


Figure 5. A vascular access port (left) and the specifically designed right angle Huber infusion set.
Surgically implanted vascular access ports in the jugular veins of patients requiring repeated intravenous therapy over weeks to months are an attractive option to avoid pain from extravasation or unnecessary stress from multiple venipunctures and catheter placement (Figure 5). Vascular access ports are standard-of-care for people receiving chemotherapy. Their use in veterinary oncology is becoming more common, and now ports specifically designed for companion animals of various body sizes are available (Companion Port—Norfolk Vet Products).

Figure 6. This Boxer cross is recovering from radiation-induced acute moist dermatitis, two weeks after the end of a full course of radiation therapy for an incompletely excised infiltrative lipoma. At this stage, the therapy-induced lesion is no longer painful.
Finally, radiation is a valuable therapeutic tool, but normal tissue toxicity may result in moderate to significant pain. Mucositis is an early radiation side effect that commonly occurs with curative-intent protocols that involve daily treatments over four weeks; it can be fairly painful.1,2,7,12,19,20 It typically develops toward the end of the treatment (in the third and fourth weeks) and may persist for a few weeks after radiation is discontinued. The most common sites of painful radiation-induced mucositis are the mouth (stomatitis, glossitis) when oral or sinonasal tumors are irradiated and the large intestine (colitis, proctitis) when pelvic irradiation is performed.7,20 Moist dermatitis is occasionally observed and can also be fairly painful (Figure 6).7,20 Computerized planning and precise analysis of dose distribution help prevent severe early radiation side effects to normal tissues. Occasionally, pain may result from late side effects of radiation therapy, including osteoradionecrosis causing pathologic fracture and peripheral neuropathies.20


The authors thank Drs. Kurt A. Grimm and William J. Tranquilli for critically reviewing this manuscript.

Louis-Philippe de Lorimier, DVM
Timothy M. Fan, DVM, DACVIM (internal medicine, oncology)
Department of Veterinary Clinical Medicine
College of Veterinary Medicine
University of Illinois
Urbana, IL 61802


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3. Slavin KV, Tesoro EP, Mucksavage JJ. The treatment of cancer pain. Drugs Today 2004;40:235-245.

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5. Gaynor JS. Pain management for the oncology patient. In: Withrow SJ, MacEwen EG, eds. Small animal clinical oncology. 3rd ed. Philadelphia, Pa: WB Saunders, 2001;219-232.

6. Gaynor JS, Muir WW. Handbook of veterinary pain management. St. Louis, Mo: Mosby, 2002.

7. Kyles AE, Ruslander D. Chronic pain: osteoarthritis and cancer. Semin Vet Med Surg (Small Anim) 1997;12:122-132.

8. Lascelles BD. Relief of chronic cancer pain. In: Dobson J, Lascelles BD, eds. BSAVA manual of oncology. 2nd ed. Cheltenham, UK: BSAVA Publications, 2003;137-151.

9. Lascelles BD. Interaction of pain and cancer, and principles of alleviation of cancer pain in dogs and cats, in Proceedings. Amer Coll Vet Intern Med 2003;497-499.

10. Lester P, Gaynor JS. Management of cancer pain. Vet Clin North Am Small Anim Pract 2000;30:951-966.

11. Tranquilli WJ, Grimm KA, Lamont LA. Pain management for the small animal practitioner. 2nd ed. Jackson, Wyo: Teton NewMedia, 2004.


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