Skin cancers are seen in horses, and many methods and technologies have been used to treat them. One of the more recent strategies is intralesional chemotherapy, or placing a chemotherapeutic agent directly in the tumor to kill the abnormal cells. At the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla., Christina Hewes, DVM, MS, Dipl. ACVS, a practitioner in Alamo, Calif., discussed the newest twist on this approach–placing bioabsorbable beads of the chemotherapeutic agent cisplatin in a tumor for a slow release of chemotherapy.

The advantages, she noted, include greater safety for the practitioner than reconstituting and injecting a liquid solution into the tumor (cisplatin + sesame oil emulsion) and the possibility that fewer treatments are required (two compared to four treatments recommended for the liquid approach).

Cisplatin Bead

Placing bioabsorbable beads of the chemotherapeutic agent cisplatin in a tumor allows for a slow release of chemotherapy.

The beads are 3 mm wide and contain 1.6 mg of cisplatin. Large tumors (more than 1.5 cm wide) are surgically removed (debulked) before bead placement. Beads are placed in the incision at 1.5-cm intervals in most tumors, and at 2.5-3-cm intervals for tumors around the eye. Hewes prefers bioabsorbable sutures when closing the wound to avoid skin disruption with suture removal.

Horses are treated every 30 days until the tumor does not regrow; most horses in this study received two treatments. Any wound drainage is cleaned by a veterinarian wearing chemotherapy gloves to minimize exposure to cisplatin, and materials are disposed of in biohazard containers.

At the Marion duPont Scott Equine Medical Center in Leesburg, Va., 40 of