Equine sarcoid: BCG immunotherapy compared to cryosurgery in a prospective randomised clinical trial

A total of 30 horses with single or multiple sarcoid tumors of the skin were randomly divided into three treatment groups: (i) cryosurgical treatment, (ii) intralesional immunotherapy with a live BCG vaccine, (iii) intralesional immunotherapy with a BCG cell wall preparation. Complete tumour regression was obtained in all 10 cryosurgically treated horses, in 6 of 10 live BCG treated horses, and in 7 of 10 BCG cell wall treated horses. One live BCG and 2 BCG cell wall treated horses showed partial tumour regression of more than 50% of the tumour area. Eleven horses with sarcoid tumours were not eligible for random allocation in the trial because unfavourable site or size of the tumour precluded cryosurgical treatment. These animals were treated with BCG cell wall vaccine except for 1 animal, which was treated with live BCG. In 4 cases this treatment was combined with cytoreductive surgery of the tumour. In this prognostically unfavourable group 8 animals showed complete tumour regression and 3 animals did not respond. Regression after BCG immunotherapy appeared to correlate with size (larger tumours worse response) and localization of the sarcoid (less favourable results in the limb), and increase in peripheral blood leucocytes after the first injection. Horses with a positive delayed type hypersensitivity reaction to PPD before the start of treatment showed a tendency to more favourable prognosis than PPD negative horses. No correlation was present between regression and single or multiple presence of sarcoids, increase in body temperature after injection of BCG and the formation of specific antibodies to BCG. None of the cured animals have shown tumour recurrence 3 to 40 months following treatment.