Molecular subtyping improves breast cancer diagnosis in the Copenhagen Breast Cancer Genomics Study

BACKGROUNDIntrinsic molecular subtypes define distinct biological breast cancers and can be used to further improve diagnosis and risk allocation.METHODSThe Copenhagen Breast Cancer Genomics Study (CBCGS) prospectively included women diagnosed with breast cancer at Rigshospitalet from 2014 to 2021. Eligible patients were females with a primary invasive breast cancer (T1c, if N0M0; otherwise, any T, any N, or any M stage) and no prior malignancy. All patients underwent molecular profiling with the CIT256 and PAM50 molecular profile.RESULTSIn the study period, 2,816 patients were included in the CBCGS. Molecular subtyping showed an increase in nonluminal (molecular-apocrine, luminal C, and Basal-like) as compared with luminal (luminal A, luminal B, and Normal-like) subtypes with increasing stage from I to IV. Across all stages, we found a significant difference in survival among subtypes; 91% of patients with LumA were alive at 5 years compared with 91% for LumB, 84% for LumC, 82% for mApo, and 80% for Basal-like. We identified 442 tumors (16%) that were discordant in subtype between CIT256 and IHC. Discordant subtype proved to be a risk factor of death among patients with IHC luminal breast cancer (hazard ratio [HR], 2.08; 95% CI, 1.51-2.86) in a multivariable Cox regression analysis. Discordance occurred more often among patients with N3, stage IV, or grade III disease.CONCLUSIONOur findings indicate that molecular subtypes are a predominant classification for survival. Assessment is particularly crucial for patients with IHC luminal breast cancer with known high-risk factors, since they are at an increased risk of harboring an aggressive molecular subtype.

Development and Methodological Validation of a Modified Staging System for de Novo Metastatic Breast Cancer

Importance

Validation of a new method for prognostication of de novo metastatic breast cancer (dnMBC) to better reflect the heterogenecity of the disease.

Objective

To perform external methodological validation of the Plichta staging system, a novel prognostic system for de novo metastatic breast cancer (dnMBC).

Design, Setting, and Participants

This retrospective cohort study used a multicenter, nationwide, population-based Danish Breast Cancer Group database to validate the new method. Participants were patients with dnMBC diagnosed between 2010 and 2019. Data were analyzed from April to June 2023.

Main outcomes and measures

A recursive partitioning analysis (RPA) was performed, as demonstrated by Plichta and colleagues, to group patients with similar overall survival (OS) based on clinical factors. The main outcome was to group patients into 4 prognostic groups based on 3-year OS as stage IVa, greater than 70%; stage IVb, 50% to 70%; stage IVc, 25% to less than 50%; or stage IVd, less than 25%. Bootstrapping was applied for 1000 iterations, with final stage assignments based on the most commonly occurring assignment.

Results

A total of 1859 women were included with a median (IQR) age of 69 (57-77) years. With a median potential follow-up of 89.9 (95% CI, 86.4-95.1) months and a median OS of 31.7 (95% CI, 29.5-34.1) months, the RPA stratified patients into 10 groups, with organ sites, estrogen receptor status, and human epidermal growth factor receptor 2 status as the key clinical factors. Three-year survival rates ranged from 62% (95% CI, 56%-69%) to 8% (95% CI, 3%-21%), which were further combined into 3 stage groups: IVb, 59.4% (95% CI, 56.2%-62.8%); IVc, 39.4% (95% CI, 36.2%-43.0%); and IVd, 15.4% (95% CI, 11.2%-21.3%) (P < .001). Following bootstrapping, an IVa group emerged, resulting in 4 stage groups with separate 3-year OS rates identified as IVa, 75.8% (95% CI, 67.8%-84.7%); IVb, 58.8% (95% CI, 55.5%-62.3%); IVc, 39.2% (95% CI, 35.8%-43.0%); and IVd, 14.4% (95% CI, 10.8%-19.4%) (P < .001).

Conclusions and relevance

These findings provide external and independent validation of the methods applied in the novel Plichta staging system for dnMBC. This could guide future revisions of the current American Joint Committee on Cancer staging guidelines and may be incorporated as a stratification factor in clinical trials.

Adjuvant treatment with trastuzumab of patients with HER2-positive, T1a-bN0M0 breast tumors: A systematic review and meta-analysis

The benefit of adjuvant trastuzumab treatment in patients with HER2-positive breast tumors ≤ 10 mm without lymph node involvement (T1abN0) is insufficiently investigated. The aim of this systematic review and meta-analysis was to examine if adjuvant trastuzumab improves the prognosis in these patients. Databases were searched to identify interventional and observational studies evaluating the effect of trastuzumab on breast cancer specific survival (BCSS), disease free survival (DFS), distant recurrence free survival (DRFS), overall survival (OS) or recurrence free survival (RFS). Twelve studies examining the effect of trastuzumab and nine control studies without trastuzumab were identified (n = 6927). Median follow-up was 36-123 months. Significantly improved DFS (Hazard Ratio (HR) 0.14, p < 0.0001) and OS (HR 0.17, p = 0.011) were found for patients receiving trastuzumab and chemotherapy compared to no trastuzumab/chemotherapy based on four and two studies. The prognosis was good even for patients without trastuzumab treatment: 5-year DFS 88.3% and 5-year OS 95.9%.

Benefit of adjuvant chemotherapy and trastuzumab in patients with HER2-positive, node-negative breast tumors ≤ 10 mm: a nationwide study

PURPOSE

The purpose of this study was to evaluate the effect of chemotherapy and trastuzumab on invasive disease-free survival (iDFS) and overall survival (OS) in patients with human epidermal growth factor receptor 2 (HER2) positive, T1abN0 breast cancer.

METHODS

In the Danish Breast Cancer Group database, patients with HER2-positive, T1abN0 tumors diagnosed between 2007 and 2016 were identified. Cox proportional hazards analysis was performed to analyze the association between adjuvant chemotherapy and trastuzumab and iDFS and OS.

RESULTS

Of 605 patients included in the analyses, 465 patients received chemotherapy and trastuzumab and 140 patients did not. Chemotherapy and trastuzumab did not improve iDFS or OS significantly in adjusted analyses. 5-year iDFS was 92.3% vs. 89.9%, Hazard ratio (HR) 1.01 (p = 0.98), and 5-year OS was 97.4% vs. 94.3%, HR 0.60 (p = 0.15), chemotherapy and trastuzumab vs. no chemotherapy/trastuzumab. In unadjusted analyses, significant treatment benefit on OS was found in patients with T1b tumors. The largest absolute treatment benefits were found in patients with T1b tumors and estrogen receptor (ER) negative tumors, respectively, whereas treatment effects in patients with T1a tumors and ER-positive tumors, respectively, were limited.

CONCLUSION

Adjuvant chemotherapy and trastuzumab did not improve OS or iDFS significantly in patients with HER2-positive, T1abN0 breast cancers in adjusted analyses. In unadjusted analyses, significant OS benefit was found in patients with T1b tumors. The largest absolute benefit was observed in patients with T1b tumors and ER-negative tumors, respectively, whereas the effect was limited in patients with T1a tumors and ER-positive tumors, respectively.

Synchronous bilateral breast cancer: a nationwide study on histopathology and etiology

PURPOSE

The aim of the present study was to describe histopathologic characteristics of synchronous bilateral breast cancer (SBBC), and by comparing SBBC to unilateral breast cancer (UBC), identify possible etiological mechanisms of SBBC.

METHODS

Patients with primary SBBC (diagnosed within 4 months) and UBC diagnosed in Denmark between 1999 and 2015 were included. Detailed data on histopathology were retrieved from the Danish Breast Cancer Group database and the Danish Pathology Register. Associations between bilateral disease and the different histopathologic characteristics were evaluated by odds ratios and estimated by multinomial regression models.

RESULTS

1214 patients with SBBC and 59,221 with UBC were included. Patients with SBBC more often had invasive lobular carcinomas (OR 1.29; 95% CI 1.13-1.47), a clinically distinct subtype of breast cancer, than UBC patients. Further, they were older than UBC patients, more often had multifocal cancer (OR 1.13; 95% CI 1.01-1.26), and a less aggressive subtype than UBC patients. Invasive lobular carcinoma was associated with having multiple tumors in breast tissue-both in the form of bilateral disease and multifocal disease, and this association was independent of laterality. No similar pattern was observed for other tumor characteristics.

CONCLUSION

We identified two etiological mechanisms that could explain some of the occurrence of SBBC. The high proportion of less aggressive carcinomas and higher age of SBBC compared to UBC patients suggests that many are diagnosed at a subclinical stage as slow-growing tumors have a higher probability of simultaneous diagnosis. The high proportion of invasive lobular carcinoma observed in bilateral and multifocal disease, being independent of laterality, suggests that these patients have an increased propensity to malignant tumor formation in breast tissue.

The Prosigna 50-gene profile and responsiveness to adjuvant anthracycline-based chemotherapy in high-risk breast cancer patients

The DBCG89D trial randomized high-risk early breast cancer patients to adjuvant CMF (cyclophosphamide, methotrexate and fluorouracil) or CEF (cyclophosphamide, epirubicin and fluorouracil). Prosigna assays were performed by researchers with no access to clinical data. Time to distant recurrence (DR) was the primary endpoint, time to recurrence (TR) and overall survival (OS) secondary. Among the 980 Danish patients enrolled, Prosigna results were obtained in 686. Continuous ROR score was associated with DR for CMF (adjusted hazard ratio (HR) 1.20, 95% CI 1.09-1.33), and for CEF (HR 1.04, 95% CI 0.92-1.18), P interaction = 0.06. DR was significantly longer in CEF compared to CMF treated patients with Her2-enriched tumors (HR 0.58, 95% CI 0.38-0.86), but not in patients with luminal tumors. Heterogeneity of treatment effect was significant for TR and OS. In this prospective-retrospective analysis, patients with Her2-enriched breast cancer derived substantial benefit from anthracycline chemotherapy whereas anthracyclines are not an essential component of chemotherapy for patients with luminal subtypes. The benefit of CEF vs. CMF correlated with increasing ROR Score.

Breast cancer mortality in synchronous bilateral breast cancer patients

Background

Evidence suggests that patients with synchronous bilateral breast cancer (SBBC), diagnosed within 4 months, have an inferior prognosis compared to unilateral breast cancer (UBC) patients. Using data from nationwide Danish clinical databases, this cohort study investigated whether the inferior prognosis could be explained by SBBC patients having a more aggressive disease, or whether the prognosis could be explained by the fact that they have two simultaneous cancers.

Methods

Patients were diagnosed from 1999–2015. The main outcome was excess mortality, subtracting background population mortality from observed mortality. Differences between SBBC and UBC patients were evaluated by rate ratios (RR) and estimated by Poisson regression.

Results

In total, 1214 SBBC and 59 177 UBC patients were included. SBBC patients had a significantly higher excess mortality than UBC patients after adjustment for age and period (RR = 1.73; 95% CI:1.44–2.08; p < 0.01) and after adjusting for characteristics of the worst tumour as traditionally done (RR = 1.31; 95% CI:1.08–1.57; p = 0.01). However, adjusting for characteristics of both tumours, using a more advanced competing risks model, no difference was observed (RR = 1.01; 95% CI:0.83–1.22; p = 0.93).

Conclusions

Our study does not support that the inferior prognosis in SBBC patients is due to having more aggressive tumours per se, but rather the combined effect of having two simultaneous cancers.

Predicting efficacy of epirubicin by a multigene assay in advanced breast cancer within a Danish Breast Cancer Cooperative Group (DBCG) cohort: a retrospective-prospective blinded study

Purpose

Anthracyclines remain a cornerstone in the treatment of primary and advanced breast cancer (BC). This study has evaluated the predictive value of a multigene mRNA-based drug response predictor (DRP) in the treatment of advanced BC with epirubicin. The DRP is a mathematical method combining in vitro sensitivity and gene expression with clinical genetic information from > 3000 clinical tumor samples.

Methods

From a DBCG cohort, 140 consecutive patients were treated with epirubicin between May 1997 and November 2016. After patient informed consent, mRNA was isolated from archival formalin-fixed paraffin-embedded primary breast tumor tissue and analyzed using Affymetrix arrays. Using time to progression (TTP) as primary endpoint, the efficacy of epirubicin was analyzed according to DRP combined with clinicopathological data collected retrospectively from patients’ medical records. Statistical analysis was done using Cox proportional hazards model stratified by treatment line.

Results

Median TTP was 9.3 months. The DRP was significantly associated to TTP (P = 0.03). The hazard ratio for DRP scores differing by 50 percentage points was 0.55 (95% CI –0.93, one-sided). A 75% DRP was associated with a median TTP of 13 months compared to 7 months following a 25% DRP. Multivariate analysis showed that DRP was independent of age and number of metastases.

Conclusion

The current study prospectively validates the predictive capability of DRP regarding epirubicin previously shown retrospectively allowing the patients predicted to be poor responders to choose more effective alternatives. Randomized prospective studies are needed to demonstrate if such an approach will lead to increased overall survival.

Prediction of exemestane benefit in patients with advanced breast cancer based on diagnostic biopsy mRNA analysis

e12532

Background: Exemestaneis a steroidal aromatase inhibitor used in the treatment of postmenopausal patients with estrogen receptor(ER)-positive adjuvant and advanced breast cancer. We aimed to determine the predictive value of a multigene mRNA-based mathematical algorithm (Drug Response Predictor (DRP)) for benefit of exemestane. The DRP is founded on measuring the full cancer transcriptome in sensitive and drug resistant cell lines compared with expression patterns in tumors and broadly validated in several studies (Wang et al. JNCI (2013) 105 (17): 1284-1291.) (Knudsen, S. et al. PLoS One (2014) 9(2): e87415.) (Christensen, TD et al. J Clin Oncol (2016) 34: suppl; abstr e12056.) (Kappel, IB et al. J Clin Oncol (2016) 34: suppl; abstr e20007.). Methods: Among 838 consecutive patients from a DBCG cohort with advanced breast cancer treated at 10 participating sites we identified 163 patients who between November 2008 and November 2015 initiated exemestane. All but one patient were ER-positive. Patients were evaluated every 3 to 4 months using CT scans and clinical examination. After patient informed consent mRNA was extracted and assayed on Affymetrix Gene Chip U133p2 arrays from formalin fixed paraffin embedded diagnostic biopsies. The primary endpoint was progression free survival (PFS). Analysis of the DRP’s ability to predict PFS was performed using a Cox regression model adjusted for treatment line. Results: Median PFS was 8.5 months. Of the 163 patients, 101 received prior adjuvant antihormone therapy and 60 did not. Data regarding adjuvant therapy was inaccessible for two patients. Hazard ratios for patients with predicted good vs. poor effect of exemestane are shown in the table. Conclusions: In a clinical setting, a mathematical algorithm using mRNA from a diagnostic biopsy can in patients unexposed to previous adjuvant endocrine therapy with statistical significance predict who will benefit from exemestane. [Table: see text]

Abstract S6-03: DBCG 07-READ: A randomized phase III trial comparing six cycles of docetaxel and cyclophosphamide (DC) to three cycles of epirubicin and cyclophosphamide followed by three cycles of docetaxel (EC-D) in patients with early breast cancer

Background: DBCG 07-READ was designed to compare sequential EC followed by D with DC in patients with early, TOP2A normal breast cancer as a retrospective evaluation of the DBCG 89D trial suggested that these patients would not benefit from an anthracycline.

Methods: This is a multicenter open-label randomized phase III trial. Three groups of women were eligible following completely resected unilateral invasive TOP2A normal (TOP2A gene to centromere 17 ratio of 0.8 to 2.0) breast cancer by mastectomy or breast conserving surgery in combination with axillary clearance or a negative sentinel node biopsy; 1: Age 18 to 39 years; 2: Age 40 to 75 years and estrogen receptor (ER) negative (&lt;10% positive) and/or HER2 positive tumor; and 3: Age 40 to 59 years and ER ≥ 10% positive and either node positive, ductal carcinoma and grade II-III, or tumor size &gt; 20 mm. Eligible patients were required to have a Charlson Comorbidity (CC) Index &lt; 2 and to be without signs of distant metastasis. Patients were randomized to receive 6 cycles of DC (docetaxel 75 mg/m2 and cyclophosphamide 600 mg/m2) every 3 weeks or 3 cycles of EC (epirubicin 90 mg/m2 and cyclophosphamide 600 mg/m2) followed by 3 cycles of D (docetaxel 100 mg/m2) every 3 weeks. In case of a CC Index of 1 or 2 chemotherapy was administered at a reduced dose-intensity. Adjuvant endocrine treatment, trastuzumab and radiotherapy were administered according to the guidelines of the DBCG. The primary endpoint was disease-free survival (DFS), and secondary endpoints were overall survival (OS) and distant disease-free survival (DDFS).

Results: Between July 2008 and December 2012 we (12 DBCG centers) randomly assigned 2006 eligible patients to DC (N=1008) or EC-D (N=998). Patient and tumor characteristics were balanced by treatment groups. The median estimated potential follow-up is 5.4 years and the 5-year DFS was 88.0%; 95% CI 85.8 to 90.0 in the EC-D arm and 87.9%; 95% CI 85.7 to 89.9 in the DC arm. No significant difference in the risk of DFS events HR=1.03; 95% CI 0.80 to 1.32; p=0.84 or mortality HR=1.11; 95% 0.79 to 1.56; p=0.55 was observed in the intent to treat analysis. Patient-reported toxicity will be compared for the two chemotherapy regimens.

Conclusion: The READ trial gives evidence to support no outcome benefit from anthracycline in patients with TOP2A normal ealy breast cancer.

Citation Format: Ejlertsen B, Tuxen MK, Jakobsen EH, Jensen M-B, Knoop AS, Hoejris I, Ewertz M, Balslev E, Vestlev PM, Kenholm J, Nielsen DL, Bechmann T, Andersson M, Cold S, Nielsen HM, Maae E, Carlsen D, Mouridsen HT. DBCG 07-READ: A randomized phase III trial comparing six cycles of docetaxel and cyclophosphamide (DC) to three cycles of epirubicin and cyclophosphamide followed by three cycles of docetaxel (EC-D) in patients with early breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr S6-03.

Abstract P1-13-03: ER, PR, HER2, and Ki67 index and responsiveness to adjuvant tamoxifen in postmenopausal high-risk breast cancer patients enrolled in the DBCG 77C trial

PURPOSE: The DBCG 77C trial compared one year of tamoxifen in postmenopausal, steroid-receptor unknown, high-risk breast cancer patients to no adjuvant systemic therapy. After a potential follow-up of 30 years we report overall efficacy for the study and results according to subtypes subsequently assessed by immunohistochemistry and FISH.

METHODS: Between 1977 and 1982, 1716 postmenopausal patients with tumors larger than 5 cm or positive axillary nodes were randomly assigned to no systemic therapy or tamoxifen 30 mg daily for one year. The main study is reported as an ITT analysis with the predefined DFS and BCM as endpoint. For multivariate analysis the Cox proportional hazards regression model was applied to assess the adjusted hazard ratio of treatment regimen, and to explore interactions. Formalin-fixed, paraffin-embedded primary breast tumor tissue blocks were available from 1548 (90%) of the 1716 participants enrolled and 1428 were assessable for ER, PR, HER2 and Ki67. The hormone receptor positive (ER and/or PR) cancers were defined as luminal A if Ki67 low and HER2-negative; as luminal B if Ki67 high or HER2-positive; and otherwise as HER2 positive or triple negative.

RESULTS: In the intent-to-treat (ITT) population one year of tamoxifen improved the disease-free-survival (DFS) (Hazard ratio (HR) = 0.87; 95% CI 0.77-0.98), the recurrence-free-survival (RFS) (HR = 0.79; 0.69-0.90) and reduced the breast-cancer-specific-mortality (BCM) (HR = 0.83; 0.73-0.93). Recurrence-free survivals were improved significantly by tamoxifen in luminal A (HR = 0.66; 0.53-0.84) and luminal B/HER2- (HR = 0.54; 0.39-0.74) but not in the other subsets, and with similar results for BCM with 30 years follow-up.

CONCLUSION: One year of treatment with tamoxifen significantly improves RFS and BCM in postmenopausal patients with ER positive breast cancers. The benefit from tamoxifen was not significantly different in luminal A and B subtypes.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-03.

Abstract P4-08-01: ESR1 Gene Aberrations Correlate with ER Protein Levels Measured by DCC and IHC

Background: The Estrogen receptor alfa (ER) is an established biomarker that has been studied in details on the protein and RNA level. Recently, the existence of amplifications and deletions of the ESR1 gene have been documented (1-3), although the frequency of the aberrations has been extensively debated. Here we hypothesize that a positive correlation exists between ESR1 gene copy number and ER protein content measured by both a biochemical ligand assay, dextran coated charcoal (DCC), and immunohistochemistry (IHC).

Material and Methods: From 289 primary high-risk breast cancer patients, randomized in the DBCG 77C trial between August 1977 and November 1982, ER data from DCC analyses was available. An ER positive tumor was defined as ≥10 fmol ER/mg protein (4). Archival tumor tissue was available from 257 patients. ESR1 copy number was analyzed with Dako

Histology FISH Accessory Kit (K5599, DAKO, Glostrup, Denmark) using a probe covering the ESR1 gene at 6q25 and a centromere 6 reference probe (3). IHC analysis for ER was applied on archival paraffin embedded tissue using the antibody ER1D5 (DAKO), 1:200 with a positive cut off value of 10% ER positive tumor cells.

Results: ESR1 FISH analysis was performed successfully in 215 (84%) patients. Amplification (ratio ESR1/CEN-6≥2) was observed in 47 of 215 patients (22%) and ESR1 deletion (ratio ESR1/CEN-6&lt;0.8) was observed in 69 (32%). A positive correlation of ER-DCC with both FISH ESR1 and ER-IHC was found (P&lt;0.0001). The ESR1 amplified tumors had higher average ER-DDC values compared to ESR1 normal tumors (ratio ESR1/ CEN6: 0,80-1,29) and tumors with ESR1 gain (ratio ESR1/CEN6: 1,30-1,99), while deleted tumors had lower ER-DCC values as illustrated in Figure 1.

A significant difference p=0.005 was found for the ESR1 deleted tumors compared to the ESR1 amplified tumors.

Fig. 1 Box plut showing the ER content according to ESR1/CEN-6 status

Discussion: Amplification of the ESR1 gene is associated with higher ER protein content by ER-DCC and more intense immunoreactivity by IHC while ESR1 deletions are associated with decreased content and immunoreactivity compared to tumors with normal ESR1 gene copy numbers. Major variations in ER content and immunoreactivity are however observed within tumors with a normal ESR1 copy number, and other mechanisms than gene aberrations seem to contribute. References:

1. Holst et al. (2007) Estrogen receptor alpha (ESR1) gene amplification is frequent in breast cancer Nat Genet 39: 655

2. Tomita et al. (2009) Estrogen receptor alpha gene ESR1 amplification may predict endocrine therapy responsiveness in breast cancer patients. Cancer Sci 100:1012

3. Nielsen et al. (2010) Amplification of ESR1 may predict resistance to adjuvant tamoxifen in postmenopausal patients with hormone receptor positive breast cancer. Breast cancer Res Treat, June 17 Epub

4. Thorpe et al. (1993) Short recurrence-free survival associated with high oestrogen receptor levels in the natural history of postmenopausal, primary breast cancer. Eur J Cancer 29A:971.

[Use of complementary and alternative medicine (CAM) in breast cancer patients. Efficacy and interactions]

At least one third of Danish breast cancer patients use CAM as a supplement to conventional treatment. There is no documentation for the life-prolonging or curing effect of CAM in breast cancer. Some forms of CAM may increase the quality of life or have palliative effect on symptoms. Health care personnel should be aware of potential interactions between herbal remedies and anti-cancer treatment.

[Prognostic and predictive factors for endocrine treatment in breast carcinoma]

There is a long tradition for defining prognostic factors in breast carcinoma; the classic ones being lymphnode status, tumor size, malignancy grade, and hormone receptor status. More important are the detection of predictive factors, defined as factors in the tumor which predict the effect of a certain treatment. The hormone receptors are a classic example of predictive factors for determining whether patients should be offered endocrine treatment. New predictive factors are HER2 for predicting the effect of trastuzumab and TOP2A for predicting the effect of certain chemotherapies.

Value of epidermal growth factor receptor, HER2, p53, and steroid receptors in predicting the efficacy of tamoxifen in high-risk postmenopausal breast cancer patients

PURPOSE

Few studies have examined the possible importance of biologic prognostic factors in breast cancer connected with differentiation and growth in predicting response to a specific adjuvant treatment. HER2, epidermal growth factor receptor (EGFR), and p53 have all been suggested as possible markers of tamoxifen resistance. The aim of this study was to investigate interactions between adjuvant treatment with tamoxifen and the content of EGFR, HER2, and p53 in steroid receptor-positive patients.

PATIENTS AND METHODS

A total of 1,716 high-risk postmenopausal breast cancer patients were randomly assigned to treatment with tamoxifen (868 women) or to observation (848 women) in a prospective trial (Danish Breast Cancer Cooperative Group's 77c protocol). The content of the steroid receptors and expression of p53, EGFR, and HER2 were determined by immunohistochemical analysis of paraffin-embedded tissue. The length of follow-up was 10 years. The end point for this analysis was disease-free survival.

RESULTS

Multivariate analysis demonstrated no increased risk of recurrence after treatment with tamoxifen for HER2-, EGFR-, and p53-positive, high-risk, steroid receptor-positive patients. Patients with steroid receptor-positive tumors and positive immunohistochemical staining for HER2, EGFR or p53 benefited from treatment with tamoxifen for 1 year, although the latter variable contained independent prognostic information by itself.

CONCLUSION

With the statistical power of the present randomized study, we did not find support for the hypothesis that HER2/EGFR or p53 status predicts benefit from tamoxifen treatment in estrogen receptor-positive patients with early-stage breast cancer. Thus, neither HER2, EGFR, nor p53 overexpression/accumulation should be used as a contraindication for giving tamoxifen.