Sometimes your veterinarian will advise you to just monitor a small sarcoid that has recently developed. They may suggest that you leave the sarcoid alone and watch for any signs of development or growth. Some sarcoids may stay very small without further development for years, so occasionally benign neglect is the treatment of choice. Of course, if the sarcoid starts to grow your veterinarian is likely to recommend an alternative treatment strategy.
Surgical removal of sarcoids is certainly a viable treatment but must always be done with caution as failure to completely remove the sarcoid will predispose its recurrence, often more aggressively. Surgical removal can be effective for small sarcoids in safe areas but the failure rate is relatively high. The decision to remove a sarcoid surgically weighs on many factors including the type of sarcoid, its location, vital structures near by and how the sarcoid might be impacting on the horse's life. Nodular sarcoids often respond favorably to surgical removal.
The use of liquid nitrogen to freeze a sarcoid can be used for selective cases. Cryosurgery involves rapidly freezing and then slowly thawing tissues in order to kill the rapidly dividing tumor cells whilst sparing the normal cells. It can be time consuming and is only effective on small superficial lesions such as occult sarcoids. It can also be used on sarcoid tissue left following de-bulking surgery of very large sarcoids. There is a high recurrence rate following cryosurgery so is rarely a preferred treatment choice.
Intra-lesional Cisplatin or 5-Fluorouracil
These are chemotherapy drugs that have shown good results when injected directly into sarcoids. The drug is mixed with oil to give it slow-release properties and injected 3-4 times at 2 week intervals. As cisplatin is a toxic drug, care must be taken when injecting into the sarcoid. Local swelling and inflamma
-tion often occurs such that sarcoids treated with cisplatin often look worse before they look better.
Imiquimod (Aldara cream) is an immune response modifier with potent antiviral and antitumor activity that is used for treatment of skin cancer and genital warts in humans. It has recently been used for treating sarcoids as well as aural plaques in ears, and has shown good results although it is prolonged treatment compared to other treatments. A light layer of cream is applied over the sarcoid initially three times weekly. Some local swelling usually occurs and again, sarcoids look worse before they get better. It may take 2-4 months of treatment to see a decrease in tumor size and so this is not a quick option. Cosmetic results are usually good, but can get expensive.
This method works reasonably well for nodular and fibroblastic lesions around the eyes but is much less effective elsewhere and should not be used for sarcoids on the limbs as these often become much worse for some unknown reason! Injection of BCG (used for human TB vaccination) is performed 3 times at weekly intervals. The method has significant risks and careful supportive medication is required at the time of each injection. The risks relate to the chance that the horse will react adversely to the protein in the injection.
Xterra herbal paste
Xxterra or Sarc-Off (Indian Mud from North America)
containing zinc chloride and an extract of the root of the Sanguinaria canadensis plant has been used with some success, but will cause extensive tissue irritation.
Autogenous Sarcoid Implantation (Possibly Best Treatment Option)
Surgically remove several pencil-eraser-sized samples off the surface of tumor and freeze them by immersing them in liquid nitrogen to kill the virus. Once the sections have thawed, implant them along the crest of the neck. The crest is chosen because the skin is thin and the area relatively immobile so it heals quickly and, if there is a scar or white hair accumulation, the mane will cover it. So far, this technique has been more successful than conventional sarcoid treatments. The tumors typically regress between 90 and 120 days after treatment, but some have taken as long as 180 days to subside. None of the horses thus far has had a recurrence. The horses followed the longest are still sarcoid-free nine years later.
As you can see, sarcoid treatment is not easy! If you think your horse has a sarcoid, or would like to discuss possible treatment options of your horse's sarcoids, please consult your veterinarian.
Dr. Darin Peterson, DVM, was born and raised on a horse and cattle ranch in Rosholt, S.D., and received his B.S. in Animal Science from SDSU. He concentrates most of his work time with large animals. He can be reached at 701-347-5496 or firstname.lastname@example.org.