Radiation‐killed BCG in the treatment of transplanted rat tumours

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Abstract
Growth of syngeneic transplants of methylcholanthrene‐induced sarcomas and an aminoazo‐dye‐induced hepatoma in rats was suppressed when tumour cells were injected in admixture with BCG vaccine containing living organisms, or vaccine sterilized by exposure to 1 to 3 × 106 R γ‐irradiation. Rejection of mixed inocula containing viable or radiation‐killed BCG induced immunity to further challenge with tumour cells. Also pulmonary tumour growth produced by intravenous injection of sarcoma cells was controlled by intravenous injection of living or radiation‐killed BCG. These studies indicate that radiation‐sterilized preparations may replace viable vaccine in immuno‐therapy, at least where tumour suppression results from contact with BCG. The use of sterilized vaccine in comparable clinical situations would remove any danger of the generalized BCG infection which has recently been reported in patients receiving BCG immunotherapy.