Abstract: F(ab').sub.2 or Fab fragments of antibodies to: (a) human chorionic gonadotropin (hCG), hCG alpha subunit, hCG beta subunit, or an hCG-like material; or (b) other tumor specific or tumor associated molecules, to include carcinoembryonic antigen (CEA), alpha fetoprotein (AFP), human melanoma associated antigens, human sarcoma associated antigens or other antigens, are radiolabeled with technetium-99m (Tc-99m). When the F(ab').sub.2 or Fab fragments of antibody to such tumor associated antigens are injected intravenously into a patient, the radiolabeled composition accumulates at tumor sites. The accumulation of the cancer seeking radiopharmaceutical at tumor sites permits detection by external gamma scintigraphy. Thus, the composition is useful in the monitoring, localization and detection of cancer in the body.In an alternative composition, a double antibody approach to tumor localization using radiolabeled F(ab').sub.2 or Fab fragments is utilized.

Abstract: Proteins are radiolabeled with technetium-99m in a reducing environment comprising buffered stannous chloride wherein the tin utilized to form the stannous chloride is non-oxidized, the buffered stannous chloride is purged of oxygen and the buffer comprises an alkali metal biphthalate and an alkali metal tartrate.Proteins which have been preincubated with tin are radiolabeled with technetium-99m to form a strongly bonded, non-exchangeable radiolabeled tracer substance. The radiolabeling can be accomplished immediately after pretinning, or the pretinned proteins can be freeze-dried and the radiolabeling accomplished at some time in the future when the pretinned proteins are resolubilized in a saline solution of sodium pertechnetate - TC-99m. Pretinning can be accomplished in a reducing environment comprising stannous chloride buffered with an alkali metal biphthalate and an alkali metal tartrate, this solution having been purged of oxygen to assure that the stannous chloride is non-oxidized.

Abstract: Anti human chorionic gonadotropin (anti-hCG) and/or anti human chorionic gonadotropin- beta subunit (anti-hCG-.beta.) labeled with Technetium-99M are/is administered to a human. The biodistribution of the labeled composition is monitored in order to determine whether the labeled composition accumulates at cancer sites, e.g. tumors that produce human chorionic gonadotropin (hCG), human chorionic gonadotropin-like material, and a compound similar to and/or identical to the beta-chain of chorionic gonadotropin, or mixtures thereof which would bind specifically to anti-hCG and/or anti-hCG-.beta..