Fc receptor-bearing peripheral blood mononuclear cells in breast cancer patients: a possible marker of tumour burden and prognosis.

Indirect immunofluorescence was used to identify and quantitate peripheral blood mononuclear (PBM) cells possessing high avidity Fc receptors in 105 patients upon referral to the breast cancer clinic at the Cross Cancer Institute. The cell detected was shown to be a non-adherent PBM, probably belonging to the T or null cell population. The mean percentage +/- 2 standard deviations of PBM-positive cells in 75 patients with no disease or benign breast disease was 5.3 +/- ;6.7, and this was significantly (P less than 0.001) less than the percentage found for 31 patients with breast cancer. The percentage of PBM-positive cells correlated directly with tumour burden in patient with small (less than or equal to 5 cm) tumours without regional node or extranodal metastases (5/13 had greater than or equal to 12% positive PBM) and in those with small tumours plus regional node metastases, but without extranodal metastases (8/10 had greater than or equal to 12% positive PBM). This correlation was less, however, in patients with large tumours (greater than 5 cm), and in those with extranodal metastases (4/8 had greater than or equal to 12% positive PBM), and in patients tested postoperatively (1/13 had greater than or equal to 12% positive PBM) even though 6!13 had regional node metastases at the time of surgery. Thus, this relatively simple assay, which can be done on peripheral blood samples, may turn out to be useful in patients with breast cancer as a prognostic marker insofar as it may be an indirect indicator of tumour burden preoperatively. If so, it may lead to a more aggressive postoperative adjuvant therapy approach to the subpopulation of node-negative PBM-positive breast cancer patients than is currently used for node-negative patients.