Measurement of ferritin-bearing peripheral mononuclear blood cells in cancer patients by radioimmunoassay.

A radioimmunoassay has been developed to measure ferritin bound to the surface of isolated human peripheral blood mononuclear white blood cells (PBMs) in order to investigate the possible relationship of this phenomenon to breast and other forms of cancer. The assay measures the specific binding (%SP) of affinity-purified 125I-labeled rabbit anti-Hodgkin's spleen ferritin antibody to isolated patient PBMs. A preliminary prospective, preclinical trial on 300 patients was run which included: (a) normals, benign breast disease, and medical/surgical patients as non-cancer controls; (b) postoperative primary cancer and advanced cancer in clinical remission as post cancer controls; and (c) both early preoperative breast cancer patients and cancer patients with localized recurrences or active disseminated disease as test groups. The mean %SP for the non-cancer control groups was in the range of 4.3 to 5.1 (n = 187), which was identical to that for inactive cancer or postoperative cancer, which was no evidence of recurrence. Using a %SP normal cutoff level of 6.5, which resulted in a false-positive rate of approximately 10% for both non-cancer and post-cancer control groups, only 27% of early preoperative cancers (n = 22) gave elevated %SP values. These results suggest that measurement of ferritin-PBM is inappropriate for early disease diagnosis. In contrast, 91% of patients with advanced active breast cancer and 73% of those patients with other types of advanced cancers, including tumors of ovarian, lung, colon or esophageal origin, showed elevated %SP values more than double those of post-cancer controls. The mean %SP value in active advanced cancer was 10.8 for breast (n = 12) and 10.6 for all other solid tumors investigated (n = 34). Paired patient comparisons of ferritin-PBM and plasma carcinoembryonic antigen in breast cancer showed elevations in 91% of the patients for ferritin-PBM and 67% for carcinoembryonic antigen. Overall, these results suggest that patients with advanced cancer display elevated levels of ferritin on the surface of their PBMs and that this measurement may be a useful adjunct in monitoring and evaluating the clinical status of cancer patients.