This study looked at the efficacy of meloxicam against malignant mammary gland tumors in cats when used with a doxorubicin-based chemotherapy protocol and aggressive surgery. A recent report showed that cyclooxygenase-2 (COX-2) was expressed in 96% of feline mammary carcinoma tissue samples studied but none of the normal tissue samples. Therefore, a case can be made that by inhibiting COX-2, tumor progression can be delayed or halted. Twenty-three cats were included in this retrospective study, with various stages of disease ranging from World Health Organization stages I to III. All cats underwent a unilateral or bilateral mastectomy or regional mastectomy, with corresponding inguinal or axillary lymphadenectomy depending on tumor location. Median disease-free interval or median survival time was not affected by the type of aggressive surgery. All cats also received 4 or 5 doses of doxorubicin every 3 weeks. Several cats also received vincristine or cyclophosphamide. All cats received meloxicam at a tapering dose (0.2 mg/kg SC on the day of surgery, followed by 0.1 mg/kg PO Q 24 H for 5 days and then 0.025 mg/kg PO Q 24 H for the rest of treatment). There is not a published dose for meloxicam for antitumor effects in cats, so dosing was extrapolated on the basis of predicted doses to at least partially inhibit COX-2. The authors did not appreciate significantly different disease-free intervals or survival times in the cats that received meloxicam versus those values in previously reported data. Toxicities were not definable, but mild renal effects were suspected in 4 cats.

Commentary: Meloxicam is approved for use in treating chronic pain in cats in Europe, Australia, and New Zealand. However, it is still approved only as a preemptive surgical (injectable) analgesic for cats in the United States. With this said, many practitioners believe it to be the safest and most effective—if not the only—
nonsteroidal antiinflammatory drug to use in cats. Antitumor effects would certainly be an added benefit because meloxicam has been shown to be a beneficial component to multimodal cancer protocols in humans. A nice adjunct to this study would be a prospective design that confirmed COX-2 receptors in the patients, allowed for meloxicam administration and control groups, and confirmed renal toxicity through further diagnostic testing. Because of the small sample size and the retrospective nature of this study, it is unclear whether definitive conclusions about antineoplastic properties of meloxicam can be made. It is also unclear whether meloxicam provided any other benefits to the treated population, such as analgesia or less inflammation.

Treatment of feline mammary tumors using chemotherapy, surgery, and a COX-2 inhibitor drug (meloxicam): A retrospective study of 23 cases (2002–2007). Borrego JF, Cartagena JC, Engel J. J VET COMP ONCOL 7:213-221, 2009.