Hormonal Receptor Determination of 1,052Chinese Breast Cancers

LOUIS W.C. CHOW, MBBS, MS, FRCS AND PEI HO, MBBS, FRCS

Department of Surgery, University of Hong Kong Medical Center, Queen Mary Hospital,Hong Kong

Background and Objectives: Hormonal receptors are important prog-nostic factors for breast cancer. The reported figures in the literature aremostly on Caucasians. This study analyzes the receptor profile of 1,052Chinese patients.Methods: The age of the patients ranged from 20–93 years; 48% werepremenopausal and 52% postmenopausal. Estrogen receptor (ER) andprogesterone receptor (PgR) were measured quantitatively by enzyme im-munoassay (EIA) using the rat monoclonal antibody (ABBOTT ER-EIA).Specimens with values >15 fmol/mg were considered positive accordingto manufacturer’s recommendation.Results: ER was positive in 53% and 61.6% of the pre- and postmeno-pausal women respectively (P < 0.0075); PgR was positive in 51.5% and46.2% respectively (P > 0.05). The mean values of ER were higher forpostmenopausal women (P < 0.0001) but the values for PgR were similarbetween the two groups (P > 0.05). When the values were analyzed withrespect to age, there was an increasing trend for ER. No such trend wasnoted for PgR. Subgroup analysis showed that there were more ER+PgR+tumors among postmenopausal than among premenopausal women. Tu-mors with dubious receptor status (ER+PgR− or ER−PgR+) were moreprevalent at perimenopausal age.Conclusions:Chinese patients have lower receptor values and positivityrates than those reported for Caucasians. Receptor-positive tumors tend tooccur in postmenopausal women.J. Surg. Oncol. 2000;75:172–175.© 2000 Wiley-Liss, Inc. © 2000 Wiley-Liss, Inc.

KEY WORDS: estrogen receptor; progesterone receptor; Chinese; breastcancer

INTRODUCTION

Breast cancer is one of the most common malignanciesin women. It is the second leading cause of cancer deathsamong women in Hong Kong [1]. The age-standardizedincidence rate is 34/100,000 giving a lifetime risk of 1 in27. The incidence is likely to increase further as morewomen become aware of the disease and more wouldattend breast cancer screening. The majority of patientsdeveloped cancer after the age of 40 and the incidenceincreases with age.

The occurrence of estrogen receptors (ER) in breastcancer was first documented by Korenman and Dukes[2]. Various methods of measuring these receptors werereported subsequently. The incidence of receptor positiv-ity differs when different methods are used [3]. Despite

the differences in receptor positivity rate, clinical trialshave shown that the presence of ER in the breast cancercells is associated with a beneficial response to endocrinemanipulation. Most of these studies, however, were con-ducted in western countries and few studies have beenmade on other ethnic groups. One of the reasons of thisinadequate documentation in the literature could be re-lated to the relatively lower incidence of breast canceroutside these countries. As proper demographic charac-terization of patient populations with regard to hormonal

*Correspondence to: Dr. Louis W.C. Chow, University of Hong KongMedical Center, Queen Mary Hospital, Pokfulam Road, Hong Kong.E-mail: lwcchow@hkucc.hku.hkAccepted 21 July 2000

Journal of Surgical Oncology 2000;75:172–175

© 2000 Wiley-Liss, Inc.

receptor status requires large number of patients, thelower incidence rate of breast cancer may account for theunder-reporting from centers of these countries. In thisarticle, we present our data on the hormonal receptorprofile of 1,052 patients.

PATIENTS AND METHODS

Between January 1987 and January 1996, tissue speci-mens were taken from 1,052 Chinese patients with his-tologically verified breast cancer. They were all analyzedin the Department of Surgery, University of Hong KongMedical Centre for determinations of the estrogen andprogesterone receptors status. The specimens were takenat the time of operation and snapped frozen within 30min. About 1 cm3 of the tumor was taken and kept at−80°C for a maximum of 14 days until further handling.The pulverized tissue was homogenized with a homog-enizer at 2–80°C. The homogenate was then centrifugedat 100,000 ×g for 1 hr at 40°C. The protein concentrationwas determined and adjusted to 1 mg of cytosol protein/ml with cold homogenization buffer.

Enzyme Immunoassay of Estrogen (ER-EIA) andProgesterone Receptors (PgR-EIA)

The Abbott ER-EIA and PgR-EIA monoclonal kits(Abbott Laboratories) were used for analysis. The ER-EIA assay was performed according to the manufactur-er’s instructions for analysis of cytosolic estrogen recep-tors. Specimen diluents and standards of 100ml aliquotswere incubated for 18 hr at 40°C with beads coated withanti-ER monoclonal antibodies. The unbound conjugatewas discarded. The receptor-bead complex was incu-bated for 1 hr with a second anti-ER monoclonal anti-body conjugated with horseradish peroxidase. The un-bound conjugate was discarded. The beads were nextincubated with an enzyme substrate solution (hydrogenperoxide ando-phenylenediamine? 2HCl). After 30 minat room temperature, the reaction is stopped by adding 1N sulfuric acid and the intensity of the resultant color wasmeasured by a spectrophotometer set at 492 nm. The ERconcentrations of the specimens were determined from astandard curve obtained by plotting the ER concentra-tions of the standards versus the absorbance. The PgR-EIA was performed similarly using the anti-PgR mono-clonal antibody but the incubation with anti-PgRconjugated with horseradish peroxidase was set at 40°C.

On the manufacturer’s recommendation, a cutoff valueof 15 fmol/mg cytosol protein was used. Concordancerate with steroid binding assay (SBA) was 92% when areference value of 10 fmol/mg was used for SBA and 15fmol/mg was used for the ABBOTT ER-EIA kit.

Statistical Methods

The determined values as well as positivity rates forER and PgR were analyzed with respect to age. The

pattern of hormonal receptor profile was also evaluated.Women who had not had menstruation for a year wereregarded to have undergone menopause. All analyseswere performed using the SPSS statistical package pro-gram (SPSS, Los Angeles, CA). Chi-square test (or theFisher exact test when the expected frequency was lessthan five) and the Studentt-test were used for compari-son of categorical and continuous variables respectively.Bivariate correlation was performed by means of thePearson test. The level of significance was taken at or<0.05.

RESULTS

The study was performed on 1,052 tissue specimens.The age ranged from 23–93 years, with a mean age of 55.Five hundred eighty-four (52.1%) patients were post-menopausal and the mean age of menopause was 51(range, 47–55) years.

Receptor Positivity in Relation to Age andMenopausal Status

The overall frequencies of estrogen and progesteronereceptor positivity were 54.1% and 47.4% respectively.Table I shows the frequencies with respect to the degreeof receptor positivity for both ER and PgR. The distri-bution of receptor positivity with respect to age wasshown in Figure 1. There is a higher incidence of estro-gen receptor positivity when the age of the patients in-creases. The frequency of receptor positivity was highestamong postmenopausal women with 58.9% of womenbeing positive for ER whereas the corresponding figurefor premenopausal women was 47.8%. The differencewas statistically significant (chi-square value, 12.4;P <0.001).

The changes in positivity for PgR in relation to agewere different from that of the ER. The incidence ofreceptor positivity did not change with age. The figuresof PgR positivity for premenopausal and postmenopausalwomen were 50.4% and 45.4% respectively. The differ-ence was not statistically significant.

The distribution curve for the estrogen and progester-one receptors was shown in Figure 2. The mean value forthe estrogen receptors was 86.63 (range, 0–679.2) fmol/mg; the standard error of mean was 3.7 fmol/mg. When

TABLE I. Degree of ER and PgR Positivity*

ER PgR

Negative 470 (45.9) 169 (52.6)Strongly positive 296 (15.4) 88 (27.4)Moderately positive 101 (9.9) 22 (6.9)Mildly positive 158 (28.9) 42 (13.1)

*Negative, <15 fmol/mg; mildly positive, between 15 and 50 fmol/mg;moderately positive, between 51 and 100 fmol/mg; strongly positive,>100 fmol/mg.

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analysis was performed on the mean receptor value withrespect to age, there was a higher mean value for estro-gen receptor among the older subjects (Fig. 3). The meanvalues for premenopausal and postmenopausal womenwere 58.7 and 111.9 fmol/mg respectively. The differ-ence was statistically significant by the Studentt-testwith a P-value of less than 0.001 (t-value, 8.41). Similaranalyses were performed for progesterone receptor. Themean value was 76.1 (range, 0–490.2) fmol/mg; the stan-dard error of mean was 6.37 fmol/mg. The mean receptorvalue did not show an increasing trend with age as forestrogen receptor. The mean values for premenopausaland postmenopausal women were 68.5 and 80.9 fmol/mgrespectively. The difference was not statistically signifi-cant.

Receptor Profile Patterns in Relation to Age andMenopausal Status

The estrogen and progesterone receptor profile pat-terns were classified as profile-positive with intact recep-tor axis (ER+PgR+), profile-negative (ER−PgR−), anddubious (ER+PgR− or ER−PgR+). The differences infrequencies between these groups were not statisticallysignificant. Subgroup analysis, however, showed signifi-cant difference between profile-positive and negative tu-

mors (chi-square value, 23.16;P 4 0.05). The analysiswas also performed while controlling for the menopausalstatus. For the postmenopausal women, there was a sig-nificant correlation (correlation coefficient of 0.19 andP4 0.006) between the hormonal receptor profile and age.The correlation for premenopausal women, however,was statistically insignificant. It is of interest to note thatthe frequencies for tumors with dubious receptor statuswere different between the pre- and postmenopausalwomen. The overall frequencies for ER+PgR− tumorswere 11.4% and 19.5% for premenopausal and post-menopausal women respectively and the correspondingfigures for ER−PgR+ tumors were 7.3% and 1.5%. Thisdifference was statistically significant (chi square value,9.8; P 4 0.002).

DISCUSSION

The study of hormonal receptors in breast cancer hasbeen the subject of interest in the past three decades.Much of the interest arises in the use of these receptors asprognostic and predictive factors [4]. Patients with posi-tive receptors have less aggressive tumor [5]. The ERpositive tumors are usually of lower histological gradeand lesser incidence of lymphocytic infiltration [6,7]. Es-trogen receptor status only provides prognostic valueduring the first 3 to 5 years. Subsequently, the relapse-free survival curves, and overall survival curves, mergeand even cross over. Therefore, hormonal receptors arepoor prognostic factors. They are much better predictivefactors. Metastatic breast cancer has much better re-sponse to hormonal manipulation by tamoxifen if theprimary tumors are receptor-positive [8].

The comparison between Chinese women and otherethnic groups with breast cancer have been reported. In aprevious report from our institution, the breast volume ofthe Chinese women is much smaller their Caucasiancounterparts [9]. The mean breast volume calculated forBritish women was 585.1 cm3 and that for Chinesewomen was 224.5 cm3. This may perhaps explained the10-fold lesser incidence of postmenopausal breast cancer

Fig. 1. Frequency of ER and PgR positivity in relation to age.

Fig. 2. Frequency distribution of receptor values for ER and PgR.

Fig. 3. Mean hormonal receptor value in relation to age.

174 Chow and Ho

in Chinese than in Americans [10]. In another study con-ducted in Hawaii, Chinese women with breast cancer hada significantly better survival than Hawaiian patients af-ter adjustment for stage of disease, age, and socioeco-nomic status [11]. Huang et al. [12] showed, however,that the incidence of HER-2/neu expression was higherthan the reported series for Caucasians. Moreover, theauthors also noted that node negative and ER negativetumors tend to have over-expression of HER-2/neu on-cogene that carries a worse prognosis.

The hormonal receptor profile was well documentedfor Caucasian women with breast cancer but it has notbeen reported in detail for Chinese and it would be ofinterest to determine if there are any similarities or dif-ferences between these women. In one study comparingthe incidence of receptors between Japanese and Ameri-can women, no major differences were found [13]. In thepresent study analyzing over 1,000 tumors, the ER ispositive in 54.1% of tumors tested. Although the patternfor pre- and postmenopausal women is similar, the posi-tivity rate is lower than that reported for the Caucasians[14]. The main determinant for this difference could berelated to the relatively lower incidence of receptor posi-tivity among postmenopausal Chinese women.

Of note in this study is that the positivity rate for PgRdoes not increases with age. The values as determined byEIA assay are also lower than the reported values forCaucasians [14]. The mean values for premenopausaland postmenopausal women are also not different statis-tically.

Analysis of the hormonal receptor profile shows thatthe profile-negative tumors are more prevalent amongpremenopausal women whereas profile-positive cancer ismore common among postmenopausal patients. More-over, the incidence of the relatively more favorable tu-mors tends to increase with age after menopause. Theincidence of tumors with dubious receptor status shows aslightly different pattern that there are more such tumorsfor women at perimenopausal age. The findings implythat the efficacy for hormonal manipulation will be

greater for postmenopausal Chinese women who willbenefit from the use of endocrine therapy.

In summary, breast cancers of Chinese women havelower values and positivity rates for ER and PgR thanCaucasians. The postmenopausal Chinese women alsohave a relatively lower incidence of receptor positivitythan their Caucasian counterparts.

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