Clinical evaluation of radio-labelled bleomycin for tumor detection

Investigations with bleomycin labelled with radionuclides other than ⁵⁷Co in patients with cancer and in tumor-bearing animals are described. In patients ⁵⁷Co-bleo appears to be a better tumor-seeking radiopharmaceutical than ¹¹¹In-bleo, ^99mTc-bleo or ¹⁹⁷Hg-bleo. This can be explained by a higher stability in vivo and a better tumor-seeking property of ⁵⁷Co-bleo and less disturbing activity in the cardiac pool and in bone and other normal tissues when assessing the scintigram. Results with ¹¹¹In-bleo labelled in acidic solution are not essentially different from those with ¹¹¹In-bleo labelled in neutral solution. Results of ¹⁹⁷Hg-bleo are almost identical with those of ¹⁹⁷HgCl₂ regarding the tumor-seeking effect as well as the distribution in normal tissues and organs. Probably the complex of ¹⁹⁷Hg to bleomycin is not stable in vivo. The superiority of ⁵⁷Co-bleo over ^99mTc-bleo and also over ⁶⁷Cu-bleo is confirmed by experiments on tumor bearing animals. We conclude that the indication for use of bleomycin as a tumor-seeking pharmaceutical labelled with ¹¹¹In, ^99mTc, ¹⁹⁷Hg or ⁶⁷Cu seems to be very limited.