REDUCED BONE-MARROW UPTAKE OF IN-111 LABELED MONOCLONAL-ANTIBODY AFTER RADIOTHERAPY

Uptake of indium-111 in bone marrow is seen in patients who have received In-111-labelled antibody. We report a case in which In-111 uptake was not seen in the area of previous irradiation whereas fairly high uptake was noted in other bone marrow areas. In-111-labelled monoclonal antibody, which reacts with mucin, was injected into a patient with cancer of the sigmoid colon who had received radiotherapy for uterine cervical cancer 5 years previously. Marked accumulation of the antibody was observed in the tumour. Uptake of In-111 in bone marrow was also seen except in the previously irradiated pelvic region. This phenomenon supports the idea that bone marrow uptake of In-111 is the result of transchelation of In-111 from antibody to transferrin.