Influence of O.C.T. embedding compound on determinations of estrogen and progestin receptors in breast cancer.

Estrogen receptor (ER) and progestin receptor (PR) concentrations in tumor biopsies are important predictive indicators of a clinical response to endocrine therapy of breast cancer. To assess interference of O.C.T. (optimum cutting temperature) embedding compound in assays of ER and PR by radioligand binding, we determined specific binding capacities and affinities of ER and PR in cytosols by a multipoint titration method, using split samples of 14 breast-tumor biopsies, one portion serving as untreated control, the other treated with O.C.T. There was no statistically significant difference between these two groups. We then compared these data with those of historical controls analyzed both in the presence and absence of sodium molybdate (10 mmol/L). Eighty breast-tumor specimens (mean +/- SD patients' ages, 59 +/- 14 y) embedded in O.C.T. compound and analyzed without molybdate gave ER and PR values that differed insignificantly from those for 306 samples (patients' ages, 61 +/- 14 y) untreated with O.C.T. Thirty-nine specimens (patients' ages, 58 +/- 15 y) embedded in O.C.T. compound were analyzed in the presence of molybdate and compared with the results for 288 specimens (patients' ages, 61 +/- 14 y) untreated with O.C.T. Again, there was an insignificant difference in the concentrations and affinities of receptors in the two groups. Evidently O.C.T. compound does not alter the receptor status of tumor biopsies.