Page 889 - The Veterinary Care of the Horse

Treatment

In some cases, it may be best to leave the sarcoids alone. This is especially the case if they
VetBooks.ir are small, not ulcerated and at a site that does not interfere with the use of the horse.

Approximately 1% will spontaneously resolve without treatment. Incorrect treatment can
cause the sarcoids to recur and spread. An equine vet who has experience in dealing with
these tumours is the best person to ask for advice. The recommendation will depend on a

number of factors including the number, location and type of lesions. Consideration will also
be given to the availability of equipment and facilities in your area and also the cost.

The treatment options include the following.

TOPICAL TREATMENT WITH CYTOTOXIC DRUGS

Cytotoxic creams are available that can be applied topically or injected into the sarcoid. This
is a form of chemotherapy as they contain drugs such as 5-fluorouracil, thiouracil and heavy

metals that destroy cancer cells and stop them dividing. An example is the AW5 cream from
Liverpool University, which is effective in up to 80% of cases when used as the first

treatment. It is usually applied daily or every other day for three to five treatments. The
sarcoids shrink and drop off over a period of a few weeks and leave an obvious scar.
Occasionally a horse will react to the cream with considerable swelling and soreness, which

resolves after a few days. Non-steroidal anti-inflammatory drugs such as phenylbutazone or
flunixin may be prescribed to relieve this. The cream can only be obtained and applied by a

vet.
The antiviral drug acyclovir has been shown to cause regression of 68% of small occult

tumours in one study when applied daily for 2 months. Other topical creams such as 5%
imiquimod are reported to cause tumour regression in 60% of cases. Herbal topical

preparations based on bloodroot powder and zinc chloride are anecdotally reported to be
successful at treating sarcoids. More studies need to be carried out on the efficacy of these

treatments.

RADIATION THERAPY

High dose radiation brachytherapy (HDRB)

High dose radiation (HDR) brachytherapy is a successful treatment for tumours around the
eye where treatment with cytotoxic cream or surgery is not an option. Special radiation

catheters are introduced into the sarcoid with the horse under standing sedation (Figure
18.37). The radiation dose from a safe external source is delivered over 5–10 minutes; two

doses are usually given 7 days apart. As soon as the treatment is finished the catheters are