Results of the Italian Interlaboratory Quality Control Program for Estradiol Receptor Assay

Determination of Estrogen Receptors in Human Breast Cancer: Comparison between Enzyme Immunoassay and Dextran-Coated Charcoal Method

Estrogen receptor determination was performed on 120 breast cancer cytosols, using the dextran-coated charcoal method (DCC) and an enzyme immunoassay (EIA) to compare the efficiency of the two techniques. A strong correlation was noted between ER concentrations determined by DCC and EIA (P < 0.001). The mean ER-EIA value was significantly higher than the mean ER-DCC value in premenopausal (P < 0.001) as well in postmenopausal (P < 0.001) patients.

Hormone Receptors and Breast Cancer: Correlations with Clinical and Histologic Features

The possible relationships between hormone receptor status and several clinical (age, gynecologic history, clinical stage) and morphologic aspects (histologic grade, vascular invasion, lymphocytic infiltration, necrosis, fibrosis, elastosis and lymph node metastasis) were evaluated. A highly significant correlation between estrogen receptor levels, patient age, menses regularity and postmenopausal status was found. The histologic features most significantly related to tumor receptor status were histologic grade, lymphocytic infiltrate, necrosis and elastosis. Since these same histologic aspects appear to influence prognosis in breast cancer, the prognostic significance attributed to tumor receptor levels is substantiated. Therefore the importance of this assay is confirmed, not only for its diagnostic and therapeutic purposes, but also for its prognostic value.

Estrogen and Progesterone Measurement and its Quality Control in Breast Cancer: A Reappraisal

This article illustrates the two main methods for routine measurement of cytoplasmic estrogen receptor status in neoplastic biopsy. The first is the Dextran Coated Charcoal Technique (D.C.C. Assay) which is still the method of choice in the majority of clinical laboratories for its simplicity, reproducibility and low cost. The second is a more advanced technique based on the specific binding, enzimatically displayed, of commercially available antiestrogen monoclonal antibodies (Enzyme Immuno Assay - ABBOTT).

The sui generis characteristics of endocrine sensitivity assessment on tumor tissues and the importance of decision-making connected with the assay justify rigorous quality assurance schemes. The quality control design proposed by the Italian Committee concerned the evaluation of several lyophilized preparations with scalar receptor content; this permits the identification through linear regression analysis of systematic and non-systematic errors. The Italian Committee has currently connected 50 labs from most regions of the country.

Quality Control for Estrogen and Progesterone Receptor Assay in Human Breast Cancer: The Influence of Computation Methods on Intra and Interlaboratory Variability

The importance of evaluating receptors for estrogen and progestin in human breast cancer has been pointed out by many authors. In the absence of a reference standard, receptor assays must be controlled by intra and interlaboratory quality control programs. Much interlaboratory variability exists due to non-uniform analytical protocols, non-uniform ligands, intrinsic errors and also errors in computation methods. The goals of our Italian Quality Control Program on Multicenter Trials are to standardize the analytical procedures and computation methods. Twenty Italian laboratories participated in the Quality Control Program. Each specimen was assayed for steroid receptor content according to the standardized dextran-coated-charcoal method. Data were subjected to computerized analyses by 5 different methods of calculation (Scatchard plot, direct plot, Lineweaver-Burk method, Brunauer-Emmet-Teller analysis, single-point approach). The results were than evaluated to identify intra- and inter-assay variation coefficients and to define other statistical parameters. The authors suggest different calculation methods depending on the specific experimental and/or physiopathological conditions.

Quality Assurance for Steroid Receptor Assay in Human Breast Cancer: Six Years Experience of the Italian Committee

Since 1979 the quality control design proposed by the Italian ad hoc Committee has evaluated several lyophilized preparations with scalar receptor content; this permits the identification by linear regression analysis of systematic and non systematic errors. At present 41 laboratories from most of the national regions have joined the Italian Committee. The overall results of five years application of quality assurance in Italy show that there was a different pattern of imprecision with satisfactory indexes for intralaboratory performances but major variations in interlaboratory controls. There was also a remarkable difference of variability indices between the so-called "expert" and "new" laboratories; this problem can be reduced with practical seminars for new centers. On the basis of the results and experience achieved the Committee is starting another program of quality assurance for different new methodologies to provide guidelines for international working reference standards.

Identification of the major sources of error in estrogen receptor measurements for individual laboratories using both tissue and cytosol samples

The major sources of error between laboratories performing estrogen receptor measurements in tissue samples were identified for 17 participating laboratories in a trial conducted by the Australasian Quality Assurance programme. Both tissue and cytosol samples were provided, and the In-House assays were compared with the ER-EIA kit (Abbott Laboratories, U.S.A.) as a reference assay. For both the In-House and Abbott assays, tissue samples resulted in a between laboratory CV of about 55% and a within laboratory CV of about 30%. In contrast to tissue samples, the between laboratory CV for cytosol samples was reduced to 41% for the In-House assays and to 33% for the Abbott assay, whereas the within laboratory CV was reduced to 10% for both types of assay. The different methods of tissue homogenization by themselves were not found to be sources of error, and protein extraction efficiency from tissue was strongly correlated with protein measurement (P less than 0.0005). The major sources of error due to protein measurement, cytosol preparation, In-House and Abbott assays were evaluated for individual laboratories. The results indicated absence of any major sources of error for four laboratories, while one, two and three or more sources were indicated for seven, three and three laboratories respectively. The conclusion that about half the participants need to improve their ER assays was confirmed by three independent reviews. Furthermore, the trial demonstrated that tissue samples are essential as quality assurance material for a realistic assessment of ER assays in biopsy specimens.

Sources of improvement in between laboratory variation in estrogen and progestin receptor measurement using tissue samples during the Australian Quality Assurance Programme

Tissue and cytosol samples were compared as quality control material for assessment of between and within laboratory error in measurement of estrogen and progestin receptors (ER and PR) in a series of four trials for a total of 17 participating laboratories during the Australasian Quality Assurance Programme. For tissue samples, a substantial reduction in between laboratory CVs for both ER and PR from about 90 to 50% was achieved during the programme. In contrast, for cytosol samples a substantially lower between laboratory CV of about 30% was obtained. Tissue sample heterogeneity could be excluded as a major source of variation between laboratories. The likely source of the observed improvement in CV for tissue samples during the trials was due to a reduction of the initial under-estimation of receptor concentration in tissue samples by some of the participants. Although cytosol preparation from tissue samples was shown to be one major source of error, other sources of error such as the receptor assay itself and the associated protein measurements were identified. It is concluded that fragmented tissue samples are essential for a realistic assessment of between laboratory error in receptor measurements in biopsy material such as obtained from clinical breast cancer samples.

Estrogen and progesterone receptor assays in human breast cancer: sources of variation between laboratories

The importance of cytosol preparation as a source of inter-laboratory variation in estrogen (ER) and progesterone (PR) receptor measurements was evaluated together with protein measurements and receptor assays for five laboratories in Sydney, Australia, using pooled, fragmented human breast cancer samples. Protein measurement was only a minor source of variation between the laboratories with a CV of 13%. For ER measurements, sources of variation due to either assay or cytosol preparation methods contributed 40 and 39% CV each. However, the variation due to assay method was reduced to 25% CV when the results from one laboratory with a known effect of a different ER assay protocol were excluded, suggesting that assay standardization could readily reduce this source of variation. In contrast, the source of a large cytosol error (39% CV) could not be identified. Variations in PR results were similar to ER, but the sources could not be accurately estimated. It is concluded that cytosol preparation as well as assay methods were major sources of between laboratory variation and need to be further investigated and standardized. This approach should reduce these sources of variation since it was found that the within laboratory cytosol and assay variations were only 13 and 18% CV, respectively, for the ER measurements.

TS/A: a new metastasizing cell line from a BALB/c spontaneous mammary adenocarcinoma

A metastasizing mouse cell line (TS/A), originated from a mammary adenocarcinoma which arose spontaneously in a BALB/c female retired breeder, has been established in vitro. It displayed a remarkable morphologic heterogeneity, which is evident in plastic adherent cultures (cell types ranging from epithelial-like to fibroblast-like) as well as in semi-solid agar cultures. The TS/A line exhibited the presence of specific cytoplasmic estradiol receptor, with a binding activity of 16 fmoles/mg cytosol protein. The in vivo growth pattern was as follows: a s.c. inoculum of 105 cells caused a 100 per cent tumor take and kill in syngeneic animals; mean survival time was 54 +/- 1 days; it did not show significant transplant immunogenicity in syngeneic animals; it was able to give rise to both spontaneous lung metastases and artificial lung colonies; it had a high capacity to grow in H-2 matched, minor histocompatibility antigen incompatible hosts (10(6) cells killed 100 per cent DBA/2 mice in 58 +/- 2 days). This line of spontaneous mammary tumor cells is proposed as a useful model for studies on the heterogeneity of the neoplastic population in relation to metastatic spread, on tumor immunogenicity, and on therapy of mammary neoplasia.

Standardization of steroid receptor assays in human breast cancer--IV. Long-term within- and between-laboratory variation of estrogen and progesterone receptor assays

One batch of lyophilized calf uterine cytosol was analyzed for estrogen and progesterone receptor (ER and PgR, respectively) content by 12 members of the EORTC Receptor Group on three different occasions over a total study period of 1 yr: One vial was included with each of 20 consecutive batches of routine tumor analyses between December 1983 and May 1984. Two vials were simultaneously assayed between July and August 1984 (within-run variation). One vial was analyzed at the end of 1984 (November-December). The overall mean ER and PgR values did not change systematically over the total study period of 1 yr. Within the various laboratories, the between-run variations of both ER and PgR assays were considerable and differed from one institution to another (7-26%). For both ER and PgR measurements the average within-run (n = 2) and between-run (n = 20) coefficients of variation were similar (8-9% and 16-17%, respectively). Comparison of the results from multiple sequential assays (c.v. = 12.9%) with those from single assays (c.v. = 21.2%) showed that about 60% of the between-laboratory variance in ER could be explained on the basis of the between-run variance. With regard to PgR analysis, however, the between-laboratory variance decreased only 25%. Standardized use of one type of protein assay (Coomassie brilliant blue) and a standard protein solution (human serum albumin) has decreased the between-laboratory variation of the protein analysis results to less than 15%.

Dexamethasone modulation of in vitro growth pattern and of lung colonization ability in clones of a metastatic BALB/c mammary carcinoma cell line

The expression of steroid receptors and the in vitro responsiveness to steroids were used to investigate the cell heterogeneity of a BALB/c mammary carcinoma cell line (TS/A) by means of its high- and low-metastatic clones previously selected in vitro. All the clones studied contained appreciable levels of receptors for oestrogens and for glucocorticoids. The in vitro responses of clones to 17 beta-oestradiol were very poor and comparable; conversely, a heterogeneous pattern of responsiveness to glucocorticoids was observed. In the presence of dexamethasone, the in vitro growth of high-metastatic clones was either unaffected or stimulated and dome formation was significantly increased. Dexamethasone treatment of low-metastatic clones caused inhibition of in vitro proliferation and a morphological shift from a fibroblast-like growth pattern towards the epithelial phenotype. One out of the three low-metastatic clones tested acquired the ability to form domes in the presence of dexamethasone, albeit sporadically. The in vitro treatment with dexamethasone significantly increased the lung colonization ability of the two low-metastatic clones studied, whereas no significant effect was observed with high-metastatic clones. Data presented here suggest that TS/A cell line consists of heterogeneous populations with peculiar proliferative and differentiative responses to glucocorticoids.

Inter-laboratory quality control of estrogen and progesterone receptor assays in breast cancer tissue using lyophilised cytosols

In 1981 a quality control (QC) program for estrogen and progesterone receptor assays was organized among six laboratories in Ontario, Canada. Twenty-three vials of lyophilised cytosol prepared from human breast tumor tissues were analysed by each laboratory over a two-year period. Samples of each batch of QC material were analysed at least twice: either in the same batch or on separate occasions. The present study demonstrates the stability of the QC material, defines the relative accuracy of the receptor assays, and provides estimates of within-batch and between-batch precision of the receptor assays.

Standardization of steroid receptor assays in human breast cancer--II. Samples with low receptor content

Four different lyophilized cytosols with low receptor content were assayed for estrogen and progesterone receptors by 13 laboratories in 7 countries. Each sample was analyzed on three different working days. Three laboratories reported unsatisfactory ER results, whereas the other 10 participants were in good agreement. Employing a cut-off limit of 10 fmol/mg cytosol protein, 95% agreement of ER-positivity was achieved for the two samples with the lowest receptor contents (18 and 21 fmol/mg cytosol protein). For estrogen receptor analyses the inter-laboratory coefficients of variation ranged between 15 and 18%. Both the intra- and inter-laboratory variations and the rate of concurrence on receptor status were less satisfactory for the progesterone than for the estrogen receptor analyses. The variation in protein results among the participating 13 laboratories is decreased to 10%. It is concluded that multi-center clinical trials based upon the estrogen receptor status assigned by individual laboratories are feasible.

Standardization of steroid receptor assays in human breast cancer--I. Reproducibility of estradiol and progesterone receptor assays

Four different lyophilized cytosols were analyzed for estrogen and progesterone receptor content by 13 laboratories. Three of the cytosols were assayed on 9 consecutive working days. The fourth cytosol was analyzed 3 times. All laboratories used the same methods of receptor and protein assays. Estradiol and progesterone receptors were measured by Scatchard analysis with centrally provided radioactive ligands and employing charcoal adsorption of free steroid. Protein was assayed by the Bradford technique with the same lots of Coomassie brilliant blue and human serum albumin standard. All participating groups except one produced receptor results (fmol/ml cytosol) with less inter-laboratory variation than in previous trials. Recalculation of the raw data of all participants by a common computer program further reduced this inter-laboratory variation. The discrepancies between the reported and recalculated receptor binding data are discussed. The intra-laboratory variation was sometimes surprisingly high and occurred at random. Single-dose saturation assays showed good agreement with multipoint Scatchard assays for the high receptor-positive samples, while poor agreement was observed for the heat-inactivated, receptor-negative sample. The use of common reagents and methodologies diminished the inter-laboratory variation coefficients of the protein assay to 14-17%; however, the protein estimation still needs to be improved.

Quality control of estrogen receptor assays in The Netherlands

Lyophilized receptor-positive tissue powders and cytosols, prepared from calf uterus and human breast tumor tissue, are used to assess the validity of routine dextran-coated charcoal estrogen receptor assays. Since 1978 lyophilized reference preparations have been analyzed twice yearly by 18 laboratories in the Netherlands. During 8 consecutive trials 20 different lyophilized samples were studied. The inter-laboratory variability of estrogen receptor results decreased with time. Most laboratories found receptor values around the median value of all groups together, though some participants consistently reported estrogen receptor values that were higher or lower than the median. The variability of estrogen receptor results between labs seemed to be associated with cytosol dilution, determination of non-specific binding, concentration and volume of dextran-coated charcoal, and the use of single dose assays or Scatchard analysis. The agreement on the presence or absence of estrogen receptors was more than 98% for lyophilized reference samples with high receptor content. For samples with low receptor content 85% agreement was observed, while 12% of the assays performed on receptor-negative material were reported to be estrogen receptor-positive. The use of the same protein determination (Coomassie Brilliant Blue) and human serum albumin standard has decreased the interlaboratory variation coefficient of the protein results to 7.5%.