here - Australian College of Veterinary Scientists

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In practical terms, those commonly used are iridium 192 and gold 198 which
are both gamma emitters.
Strontium 90, a beta particle emitter has a limited penetration of 3mm, so it's
use is restricted to those tumours following very careful debulking or to cleanup
surface cells in conjunction with implants. When applied to the target area
following post surgical ablation of the tumour, Strontium 90 in an applicator
has been successfully used for some sarcoids and ocular squamous cell
carcinoma
8. Photodynamic Therapy
The therapeutic potential of the photodynamic compound, hypericin, in the
treatment of equine sarcoids has been evaluated.In vitro cytotoxicity on three
equine cell lines to phototoxic effect was comparable to that on different
highly sensitive human cell lines and significantly influenced by the energy
density used although independent of the cell type.
In vivo anti tumoural action of photodynamic therapy using hypericin was
used experimentally on three equine sarcoids in a donkey. With either a 0.3%
hypericin solution in polyethylene glycol (PEG400)/H2O L/L. or a 0.3%
hypericin solution in DMSO/H2O L/L was used.
Intratumoural injections were performed every 5days under short acting GA.
Mean dosage of hypericine was 0.7mg/cm3 tumoural tissue. Tumours were
illuminated over 30 min each day with a light delivery by a KL 1500 cold light
source at 1 cm distance from the surface (results in an energy density of 72
J/cm2.) . However, this is only for a total of 25 days.
81% reduction in tumour volume was obtained at the end of therapy and 2
months later, a 90% reduction was observed. Further experimental work
should be performed, but these results suggest that photodynamic therapy
using hypericin has a potential for the non-invasive treatment of equine
sarcoids. (Martens 2000)
9. Radio frequency hyperthermia
This modality has been used in equine sarcoid and squamous cell carcinoma
and is most successful in small tumours Reports of treatments indicate repeat
treatments are common and the method is not gained wide acceptance
10. Chemotherapy
Many and varied compounds of inorganic tissue poisons such as arsenic,
mercury and antimony, and their combinations have been used to treat
sarcoids. More recently podophyllin, methotrexate, 5-fluorouracil, cisplatin
ACVSC Proceedings Dermatology Chapter Science Week 2005