Evolution of immunoreactivity of monoclonal antibodies H222 and/or D547 used in the detection of breast cancer estrogen receptors. Varying reactivity of receptor isoforms

Paraffin section immunocytochemistry and cytosol-based ligand-binding assays for ER and PR detection in breast cancer: the time has come for more objectivity

The importance of the receptor level in breast cancer as an indicator of hormone response has been extensively studied for more than 20 years. Besides cytosol-based ligand-binding assays (dextran-coated charcoal assay, DCC), new methods using monoclonal antibodies raised against estrogen and progesterone receptors allow for the detection of receptors both in cytosol extracts (enzyme immunoassay, EIA) and in tissue sections (immunocytochemical assay, ICA). The biochemical assays (DCC and EIA) as well as the immunochemical detection (ICA) have specific qualities and produce original information which is useful for the therapeutic decision. While DCC gives a measure of the receptor level, whatever the real source of synthesis (normal and/or neoplastic tissue), ICA locates the positive cells and their relative proportion in the tumor. Both methods present their own advantages and disadvantages which are summarized in this study.

Prospective evaluation of prognostic factors in operable breast cancer

In 215 patients with operable breast cancer (T1-T3, N0-1, M0) and no other or previous cancer, presenting to a single breast unit, sufficient tumour was available for the prospective determination of four putative biochemical markers of prognosis: oestrogen receptor (ER) activity, cathepsin D (cath D), epidermal growth factor receptor (EGFR) activity and cyclic AMP-binding proteins (c-AMP-b). There were significant inter-relationships between ER and EGFR (r = -0.26), c-AMP-b and cath D (r = +0.32) and ER and c-AMP-b (r = +0.14). After follow-up (median 36.2 months), a total of 55 recurrences (18 locoregional only) and 35 deaths were recorded. By univariate analysis, up to 10 of 18 biochemical, clinical and histopathological variables of potential prognostic value were significantly related to disease-free interval or death, but by multivariate analysis only oestrogen receptor concentration and node status contributed significantly to risk of both distant recurrence/death; in addition, tumour size made a small contribution to the risk for a distant recurrence only. Only two parameters, tumour grade and ER concentration, were significantly related to risk of locoregional recurrence by univariate analysis, but by multivariate analysis, only tumour grade was important. It is concluded that tumour ER concentration, axillary nodal status and tumour grade remain as the most important prognostic factors in the early years after presentation of operable breast cancer, with a minor influence of tumour size. At this time, the prognostic significance of quantitative measurements of ER concentration, carefully controlled for the quality of both assay and tumour specimen, is probably greater than is generally appreciated. We have yet to identify other factors, which add significantly to the short-term prognostic value of these key features.

An improved statistical approach: can it clarify the role of new prognostic factors for breast cancer?

Recently, there has been a proliferation of new biomarkers, some of which may lead to an improved prognostic index or may influence treatment selection. However, there are methodological and statistical issues that require attention in assessing the role and use of these prognostic factors. Between 1977 and 1986, 1097 primary breast cancer patients were accrued for multidisciplinary research at the Henrietta Banting Breast Centre, Women's College Hospital; follow-up to 1990 is complete for 96% of the patients. Data for these patients are used here to illustrate strategies: (1) for the comparison of results from diverse assessments of biomarkers; (2) for the improved comparability of inter-laboratory results; (3) for the examination of the results from monoclonal or polyclonal antibody assays for possible clinically relevant bimodality; (4) for good statistical resolution of overlapping distributions; (5) that involve the use of quantitative values for prognostic factors whenever possible; and (6) for improved multivariate analyses. Good data handling and analyses may enable more accurate and rapid assessment of new prognostic factors, thereby expediting and improving their clinical application.

An investigation of cut-points for primary breast cancer oestrogen and progesterone receptor assays

Oestrogen and progesterone receptor (ER and PgR) assay values are frequently used in medical decision-making for breast cancer patients. We have proposed statistical standardization of receptor assay values to improve inter-laboratory comparability, and now report the use of standardized log units (SLU) to investigate the effects of ER and PgR cut-points on time to first recurrence outside the breast (DFS). Between 1980 and 1986, there were 678 primary breast cancer patients treated at the Henrietta Banting Breast Centre (HBBC). The effects of ER and PgR cut-points were examined with multivariate analyses considering the variables: age, tumour size, nodal status, weight and adjuvant treatment. We considered receptor assay cut-points ranging from - 1.0 to + 1.0 SLU (ER between 7 and 166 fmol/mg protein; PgR between 7 and 181 fmol/mg protein). PgR was included in the multivariate prognostic models more often than ER, although patients had a better prognosis with both larger ER and PgR values. There was no best cut-point for ER or PgR, and there was strong evidence that ER and PgR should be considered as continuous rather than dichotomous (negative, positive) variables. Patient prognosis should also be more comparable with SLU.

Determination of oestrogen receptors by enzyme immunoassay. Technical differences between laboratories and their consequences

When multicentre breast cancer trials are performed, receptor analyses must be comparable both over time and in the participating laboratories. However, we show for the first time a high variability for the distribution of oestradiol receptor (ER) values measured by enzyme immunoassay (EIA) from 1987 to 1991. This variability could be explained by calibration changes in the immunoassay kits. We have also analysed the influence on ER-EIA levels of technical differences between laboratories apart from the assay itself. Many steps emerged as being critical, i.e. homogenisation buffer, homogenisation procedure and cytosol dilution. Finally, we show that addition of 4-monohydroxytamoxifen increases the apparent ER content measured by EIA in 92% of cytosols. Thus, many factors must be controlled to ensure high precision with ER-EIA assays. We have to be particularly cautious with the conformational changes that could occur during cytosol preparation and that could also pre-exist in the tumour samples. Quality controls of cytosol preparation are essential.

Use of automated smoothing and deconvolution procedures for the determination of human breast cancer estrogen and progesterone receptor isoforms, after high-performance size-exclusion chromatography

Automated smoothing and deconvolution procedures were used to analyse complex chromatographic patterns of human breast cancer estrogen and progesterone receptors, obtained by size-exclusion chromatography. By injecting, first, different known amounts of a radio-iodinated protein in a TSK G-3000 SW column, constructed complex chromatograms (twelve chromatograms) with known peak positions were obtained, and were further treated by mathematical functions to determine a smooth-deconvolution strategy, which could be used with unknown chromatographic patterns. The determination of peak areas by a "curve-fit" program showed a good correlation with the amounts of protein injected (r = 0.91). Human breast cancer estrogen receptors (56 cases) and progesterone receptors (45 cases) were chromatographed in a TSK G-3000 SW column, and further analysed with the smoothing and deconvolution procedures: eight different estrogen receptor isoforms were detected with molecular masses ranging from 530,000 [Stoke's radius (Rs) = 7.7 nm] to 23,000 (Rs = 2.6 nm), and eight progesterone receptor isoforms were observed with masses ranging from 680,000 (Rs = 8.6 nm) to 50,000 (Rs = 3.1 nm). The dissociation effect of KCl (0 to 1 M) on receptor structure yielded different proportions of receptor isoforms, but did not modify their different peak positions.

Evidence for bimodal distribution of breast carcinoma ER and PgR values quantitated by enzyme immunoassay

Breast carcinoma oestrogen receptor (ER) and progesterone receptor (PgR) values obtained by radioligand binding assays have commonly been observed to have approximate log-normal distributions. We examined the distribution of log-transformed receptor values obtained by enzyme immunoassay for 5468 primary breast carcinomas in five Ontario laboratories. In each laboratory, it was found that the frequency histograms for the log transformed receptor values were not unimodal, and generally were suggestive of bimodality. This was not affected by stratification by age or inferred menopausal status (< or = 49, > or = 50 years), and could not be explained by kit characteristics. However, the low point in the distribution varied from 5 to 63 fmol/mg cytosol protein, depending on the receptor, patient age and laboratory. The tendency towards biomodality was more distinct for ER than for PgR. It remains to be determined whether the low points on the frequency histograms have clinical relevance for discriminating between hormone-sensitive and hormone-insensitive tumours.