Pre-treatment with the anabolic steroid nandrolone decanoate (ND) increases the LD50 of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) and 5-Fluorouracil (FU) in NMRI mice. Administration of ND did not affect the anti-tumour action of CCNU against a transplantable mouse adenocarcinoma of the colon (MAC 13) or the anti-tumour action of FU against MAC 26. In both tumour lines ND had no significant effect on tumour growth. These data suggest that an increase in the anti-tumour selectivity of these agents may be produced by pre-treatment with ND
