Presurgical radiotherapy decreases the concentrations of estrogen and progesterone receptors in human breast cancer: A 200-patient study

Summary The concentrations of cytosol estrogen (RE) and progesterone (RP) receptors were evaluated in human breast cancer either pretreated or untreated by radiotherapy. Receptor sites were assayed within a week following surgery by using the classical dextran-coated charcoal technique with three saturating concentrations of (³H) 17 estradiol and (³H) R5020 and by correcting for nonsaturable binding estimated in parallel with an excess of nonradioactive ligand. Only tissue containing cancer cells as determined by a pathologist was assayed for receptors.Two nonrandomised groups were compared: a control group of 91 patients which were not treated before surgery, and an irradiated group of 108 patients which received radiotherapy (60 to 70 grays) about 2 to 4 months before surgery. Radiotherapy significantly reduced the percentage of receptor positive tumors ( 10 fmoles/mg protein) from RE 82% and RP 67% in the control group to RE 54% and RP 28% in the irradiated group.The mean concentrations of the positive receptors were also decreased by irradiation, from 238 fm/mgP and 146 fm/mgP to 55 fm/mgP and 54 fm/mgP for RE and RP respectively. This decrease was observed for all histopathological stages studied in both pre- and postmenopausal patients, and was also not dependent on cell density. Since the irradiated patients mostly had tumors of TNMT₂ and nonirradiated patients had smaller tumors (TNM T₂), we checked that the same effect of radiotherapy was found in the homogeneous group of TNM = T₂.We conclude that presurgical radiotherapy of breast cancer decreases the percentage of estrogen receptor and progestin receptor positive patients. Therefore, the assay of steroid receptors in breast cancer remains useful in predicting hormone dependency and prognosis of breast cancer when receptor concentrations are positive. But the assay is of no value when receptor concentrations are negative. New micro techniques must therefore be developed for assaying receptor before any therapy.