Just Ask the Expert: NSAIDs and tumor suppression

Dr. Fan welcomes oncology questions from veterinarians.

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With the subject line: Oncology question

Q. Do any NSAIDs besides piroxicam suppress the growth of some cancers in dogs?


Timothy M. Fan, DVM, PhD, DACVIM
A. Many nonsteroidal anti-inflammatory drugs (NSAIDs) are approved for managing postsurgical pain and osteoarthritis in dogs. Most of the NSAIDs developed for companion animals preferentially inhibit cyclooxygenase-2 (COX-2), an enzyme system responsible for the production of inflammatory lipid mediators such as prostaglandin E2 (PGE2). Interestingly, PGE2 also exerts several tumor-promoting effects, including 1) inhibition of cell death, 2) enhancement of new blood vessel formation, 3) enhancement of cell invasiveness, and 4) immune suppression.

As such, a drug that inhibits COX-2 activity and subsequently reduces PGE2 production would theoretically be useful as a chemopreventive agent and even possibly as a therapeutic anticancer agent. However, despite the substantial biologic rationale for using NSAIDs in companion animals with cancers, little evidence exists as to their utility for effectively treating macroscopic tumor burdens.

Only piroxicam, a mixed COX-1 and COX-2 inhibitor, has been shown to exert single-agent anticancer effects in a handful of tumor histologies, particularly transitional cell carcinoma.1,2 Although numerous more-selective NSAIDs are available, to date no prospective or controlled studies have been performed to evaluate potential anticancer effects of NSAIDs other than piroxicam.

Timothy M. Fan, DVM, PhD, DACVIM (internal medicine, oncology)
Department of Veterinary Clinical Medicine
College of Veterinary Medicine
University of Illinois
Urbana, IL 61802

REFERENCES

1. Knapp DW, Richardson RC, Bottoms GD, et al. Phase I trial of piroxicam in 62 dogs bearing naturally occurring tumors. Cancer Chemother Pharmacol 1992;29(3):214-218.

2. Knapp DW, Richardson RC, Chan TC, et al. Piroxicam therapy in 34 dogs with transitional cell carcinoma of the urinary bladder. J Vet Intern Med 1994;8(4):273-278.