Traditional Predictive Factors Research Articles

Abstract A15: High miRNA-26a and low EZH2 expression levels are associated with favorable outcome to tamoxifen in advanced breast cancer

Abstract Background: In breast cancer we have recently discovered that decreased EZH2 expression levels are associated with a favorable outcome to tamoxifen in advanced disease. Furthermore, EZH2 knockdown in the breast cancer cell line MCF7 resulted in estrogen receptor (ER) upregulation and increased sensitivity to anti-estrogens. Interestingly, EZH2 has been identified as target of miRNA-26a and miRNA-101. Objective: The main objective of this study is to investigate miRNA-26a and miRNA-101 for: A) their association with EZH2 and B) their predictive value in breast cancer patients treated with first-line tamoxifen monotherapy. Materials & Methods: Expression levels of miRNA-26a, miRNA-101, EZH2 and references were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in 235 ER-positive primary breast cancer specimens from patients with advanced disease. The levels of expression were related to clinicopathologic factors and disease outcome. Computations were performed with STATA and P-values <0.05 were considered statistically significant. Results: Expression levels of miRNA-26a and miRNA-101 were not correlated with age, tumor grade, tumor size, and nodal status. The miRNA-26a levels were significantly associated with progesterone (PgR) levels, HER2-status and EGFR levels, whereas miRNA-101 levels showed significant relations with PgR expression and menopausal status. The miRNA-26a and miRNA-101 levels showed an inverse relation with EZH2 mRNA levels (Spearman Rank Correlation of −0.21 and −0.15, respectively, P<0.05). As continuous variable in univariate analysis, miRNA-26a (Hazard Ratio (HR)=0.13, 95% CI: 0.06-0.28) correlated with Time To Progression (TTP), whereas miRNA-101 did not (HR=0.87, 95% CI: 0.70-1.07). In multivariate analysis including traditional predictive factors, the tertile with highest miRNA-26a levels (HR=0.51, 95% CI: 0.35-0.75) alone, and combined with the tertile with lowest EZH2 levels (HR=0.59, 95% CI: 0.41-0.85) were associated with a favorable TTP independently of traditional factors. Conclusion & Discussion: The miRNA-26a and miRNA-101 levels have an inverse relation with EZH2, but only miRNA-26a has predictive value in advanced breast cancer. High levels of miRNA-26a and low EZH2 levels are associated with a favorable outcome to tamoxifen therapy. Interestingly, estrogens repress miRNA-26a expression suggesting that ER-positive tumors have less miRNA-26a than ER-negative tumors. This contradicts, however, with the lower EZH2 levels observed in ER-positive compared to ER-negative breast cancers. To clarify this paradox, future (functional) studies will focus on miRNA-26a and EZH2 in different breast cancer subtypes and determine their activated pathways in relation with response to anti-estrogens. Citation Information: Clin Cancer Res 2010;16(7 Suppl):A15

Down Regulation of EZH2 Is Associated with ESR1 Upregulation and Response to Endocrine Therapy in Breast Cancer.

Abstract Background: We have previously identified a gene signature for resistance to first-line tamoxifen therapy in advanced breast cancer. One of these genes is Enhancer of Zeste Homolog 1 (EZH1), a member of the EZH family of which EZH2 has been identified as being prognostic. Both genes are involved in transcriptional control and epigenetic memory maintenance and act as polycomb repressors. The aim of this study is to investigate these genes for their predictive value and, if associated with clinical outcome, to evaluate the functional role in treatment response in vitro.Experimental design: Expression levels of EZH1 and EZH2 expression were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in primary breast cancer specimens and related to clinicopathologic factors and disease outcome. Functional studies were done in MCF7, a human estrogen sensitive breast cancer cell line. Expression levels of EZH2 were downregulated with siRNAs, and changes in cell numbers were determined treating with (the anti-estrogen) ICI164.384. In addition, alterations in expression levels of putative downstream genes, including the estrogen receptor (ESR1), were measured.Results: When analysed as continuous variable in univariate analysis, only EZH2 was significantly associated with therapy resistance and a shorter Progression Free Survival (PFS) in 278 patients with advanced disease treated with first-line tamoxifen monotherapy. In univariate analysis the tertile with highest EZH2 levels was associated with clinical benefit (OR=0.48, 95%CI: 0.26-0.89; P=0.02) and with PFS (HR=1.80, 95%CI: 1.32-2.46;P<0.001). In multivariate analysis including traditional predictive factors, highest EZH2 levels were independently related with a shorter PFS (HR=1.58, 95%CI: 1.10-2.26; P=0.01). Despite, EZH2 mRNA levels were not significantly correlated with metastasis free survival (HR=1.14, 95%CI: 0.98-1.32; P=0.10) in 688 lymph node negative patients who did not receive adjuvant systemic therapy.EZH2 silencing in MCF7 caused a significant decrease in cell numbers (38%, range 17-53%, N=3) whereas ICI164.384 treatment resulted in decrease of 25% (range 12-30%, N=3) compared to controls. Combining EZH2 silencing with ICI-treatment reduced cell numbers with 67% (range 54-75%, N=3, P<0.001). Interestingly, downregulation of EZH2 was associated with an almost 2-fold upregulation of ESR1 (N=6, P=0.001). This inverse relation has been confirmed in additional “in silico” analyses.Conclusion: High levels of EZH2 are associated with poor clinical outcome for tamoxifen therapy of advanced breast cancer. EZH2 silencing in MCF7 cells inhibits cell proliferation, it upregulates ESR1 levels and increases sensitivity to ICI164.384. Further validation is needed to confirm that silencing of EZH2 leads to an upregulation of the ESR1 and as a consequence to a better response to anti-estrogens. This finding sheds new light on the involvement of EZH2 in anti-estrogen treatment offering possibilities for novel management strategies. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5131.

Microsatellite Instability Predicts Clinical Outcome in Radiation-Treated Endometrioid Endometrial Cancer

To elucidate whether microsatellite instability (MSI) predicts clinical outcome in radiation-treated endometrioid endometrial cancer (EEC). A consecutive series of 93 patients with EEC treated with extrafascial hysterectomy and postoperative radiotherapy was studied. The median clinical follow-up of patients was 138 months, with a maximum of 232 months. Five quasimonomorphic mononucleotide markers (BAT-25, BAT-26, NR21, NR24, and NR27) were used for MSI classification. Twenty-five patients (22%) were classified as MSI. Both in the whole series and in early stages (I and II), univariate analysis showed a significant association between MSI and poorer 10-year local disease-free survival, disease-free survival, and cancer-specific survival. In multivariate analysis, MSI was excluded from the final regression model in the whole series, but in early stages MSI provided additional significant predictive information independent of traditional prognostic and predictive factors (age, stage, grade, and vascular invasion) for disease-free survival (hazard ratio [HR] 3.25, 95% confidence interval [CI] 1.01-10.49; p = 0.048) and cancer-specific survival (HR 4.20, 95% CI 1.23-14.35; p = 0.022) and was marginally significant for local disease-free survival (HR 3.54, 95% CI 0.93-13.46; p = 0.064). These results suggest that MSI may predict radiotherapy response in early-stage EEC.

Decreased expression of EZH2 is associated with ESR1 upregulation and response to anti-estrogens.

Abstract Abstract #6127 Background: In prostate and breast cancer high levels of Enhancer of Zeste Homolog 2 (EZH2) are associated with tumor progression. EZH2, a histone H3 methyl transferase, is part of the polycomb complex. Together with histone deacetylases (HDACs) EZH2 regulates “genome wide” gene transcription silencing. The aims of this study are a) to correlate EZH2 expression with endocrine therapy response in patients with recurrent disease treated with first-line tamoxifen monotherapy and b) to determine the role of EZH2 in endocrine therapy response using in vitro cell line models.
 Material and Methods: EZH2 mRNA levels were measured with quantitative real-time PCR (qRT-PCR) in 297 retrospectively collected hormone receptor positive (HR+) primary breast tumor specimens of patients with recurrent disease who did respond (N=110) or were resistant (N=187) to first-line tamoxifen monotherapy. In vitro, EZH2 and estrogen receptor (ESR1) expression was downregulated with siRNAs in the human breast cancer cell line MCF7 and assessed for their sensitivity to the selective estrogen receptor degrader ICI164.384 after 96hrs treatment (N=3). To establish therapy response in vitro, cell number counts were determined. All p-values are two-sided and significant if P<0.05.
 Results: In 297 HR+ breast tumors, EZH2 as continuous variable, associated significantly with poor response (OR= 0.67 [0.49-0.91]; P=0.001) and a shorter progression-free survival (PFS) (HR=1.28 [1.11-1.47], P<0.001). In the multivariate model with traditional predictive factors, the tertile with highest EZH2 levels was independently related with response (OR= 0.50 [0.26-0.98]; P=0.045) and PFS (HR=1.82 [1.33-2.49], P<0.001).
 In vitro, EZH2 downregulation in MCF7 with siRNAs showed a significant decrease in cell number compared to the mock silenced cell line (40%). Moreover, ICI treatment of EZH2 silenced MCF7 cells resulted in a 70% cell number decrease versus 23% decrease in the controls (P<0.001). In addition, EZH2 downregulation is associated with a twofold upregulation with ESR1 (P<0.001). Conversely, silencing of ESR1 in MCF7 resulted did not alter EZH2 levels but, as expected, increases HER2 protein levels.
 Conclusion: In primary breast tumors, high EZH2 mRNA levels are associated with poor outcomes after tamoxifen therapy. These results suggest that EZH2 may identify patients at risk for tamoxifen therapy failure. In vitro studies show that downregulation of EZH2 inhibits cell proliferation and on the other hand results in upregulation of ESR1 levels. The latter may explain the increased sensitivity to ICI164.384 of EZH2 silenced cells. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6127.

Emerging Biomarkers and New Understanding of Traditional Markers in Personalized Therapy for Breast Cancer

The era of personalized medicine is likely to see an escalation in the use of biomarkers to ensure breast cancer patients receive optimal treatment. A combination of prognostic and predictive biomarkers should enable better quantification of the residual risk faced by patients and indicate the potential value of additional treatment. Established biomarkers such as estrogen receptor and progesterone receptor already play a significant role in the selection of patients for endocrine therapy. Human epidermal growth factor receptor 2 (HER2) is recognized as a strong predictor of response to trastuzumab whereas, more recently, the role of estrogen receptor and HER2 as negative and positive indicators for chemotherapy has also been explored. Ki67 has traditionally been recognized as a modest prognostic factor, but recent neoadjuvant studies suggest that on-treatment measurement may be a more effective predictor of treatment efficacy for both endocrine treatment and chemotherapy. The last decade has seen the emergence of numerous multigene expression profiles that aim to outdo traditional predictive and prognostic factors. The Oncotype DX assay and the MammaPrint profile are currently undergoing prospective clinical trials to clearly define their role. Other gene expression-based assays also show potential but are yet to be tested clinically. Rigorous comparison of these emerging markers with current treatment selection criteria will be required to determine whether they offer significant benefit to justify their use.

Relevance of Breast Cancer Antiestrogen Resistance Genes in Human Breast Cancer Progression and Tamoxifen Resistance

We have previously identified a set of breast cancer antiestrogen resistance (BCAR) genes causing estrogen independence and tamoxifen resistance in vitro using a functional genetic screen. Here, we explored whether these BCAR genes provide predictive value for tamoxifen resistance and prognostic information for tumor aggressiveness in breast cancer patients. mRNA levels of 10 BCAR genes (AKT1, AKT2, BCAR1, BCAR3, EGFR, ERBB2, GRB7, SRC, TLE3, and TRERF1) were measured in estrogen receptor-positive breast tumors using quantitative reverse-transcriptase polymerase chain reaction. Normalized mRNA levels were evaluated for association with progression-free survival (PFS) in 242 patients receiving tamoxifen as first-line monotherapy for recurrent disease, and with distant metastasis-free survival (MFS) in 413 lymph node-negative (LNN) primary breast cancer patients who did not receive systemic adjuvant therapy. Concerning tamoxifen resistance, BCAR3, ERBB2, GRB7, and TLE3 mRNA levels were predictive for PFS, independent of traditional predictive factors. By combining GRB7 (or ERBB2) and TLE3 mRNA levels, patients could be classified in three subgroups with distinct PFS. For the evaluation of tumor aggressiveness, AKT2, EGFR, and TRERF1 mRNA levels were all significantly associated with MFS, independent of traditional prognostic factors. Using the combined AKT2 and EGFR mRNA status, four prognostic groups were identified with different MFS outcomes. The majority of BCAR genes, which were revealed to confer tamoxifen resistance and estrogen independence in vitro by functional screening, have clinical relevance, and associate with tamoxifen resistance and/or tumor aggressiveness in breast cancer patients.

Fibroblast growth factor receptor 4 predicts failure on tamoxifen therapy in patients with recurrent breast cancer

Tamoxifen treatment of estrogen-dependent breast cancer ultimately loses its effectiveness due to the development of resistance. From a functional screen for identifying genes responsible for tamoxifen resistance in human ZR-75-1 breast cancer cells, fibroblast growth factor (FGF) 17 was recovered. The aim of this exploratory study was to assess the predictive value of FGF17 and the receptors FGFR1-4 for the type of response to tamoxifen treatment (clinical benefit) and the duration of progression-free survival (PFS) in patients with recurrent breast cancer. mRNA levels of FGF17 and FGFR1-4 were quantified by real-time reverse transcriptase PCR in 285 estrogen receptor-positive breast carcinomas with clinical follow-up. All patients had recurrent disease and were treated with tamoxifen as first-line systemic therapy for local or distant relapse. FGF17 and FGFR1-3 mRNA levels had no significant predictive value for this group of patients. However, high FGFR4 mRNA levels analyzed as a continuous log-transformed variable predicted poor clinical benefit (odds ratio=1.22; P=0.009) and shorter PFS (hazard ratio=1.18; P<0.001). In addition, in multivariable analysis, the predictive value of FGFR4 was independent from the traditional predictive factors. Our analyses show that FGFR4 may play a role in the biological response of the tumor to tamoxifen treatment. In addition, as altered expression of FGF17 causes tamoxifen resistance in vitro, the FGF signaling pathway could be a valuable target in the treatment of breast cancer patients resistant to endocrine treatment.

TSC22D1 and PSAP predict clinical outcome of tamoxifen treatment in patients with recurrent breast cancer

Purpose Two genes, TSC22 domain family, member 1 (TSC22D1) and prosaposin (PSAP) were identified in an in vitro functional screen for genes having a causative role in tamoxifen resistance. These genes were also present in our previously established 81-gene signature for resistance to first-line tamoxifen therapy. The aim of this study was to investigate the predictive value of these genes for tamoxifen therapy failure in patients with recurrent breast cancer. Experimental Design The mRNA levels of TSC22D1 and PSAP were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) in 223 estrogen receptor-positive primary breast tumors of patients with recurrent disease treated with first-line tamoxifen therapy. The main objective of this study was the length of progression-free survival (PFS). Results High mRNA levels of TSC22D1 and PSAP were significantly associated with shorter PFS and both were independent of the traditional predictive factors (HR = 1.30, 95% CI = 1.04-1.64 P = 0.023; and HR = 1.40, 95% CI = 1.03-1.88, P = 0.029, respectively). In multivariate analysis, patients with high mRNA levels of both genes associated significantly with no clinical benefit (OR = 0.19, 95% CI = 0.06-0.62, P = 0.006) and had the shortest PFS (HR = 2.05, 95% CI = 1.29-3.25, P = 0.002). Conclusion These results confirm our previous in vitro and tumor-related findings and are indicative for the failure of tamoxifen treatment in breast-cancer patients. Both TSC22D1 and PSAP are associated with clinical outcome and may have a functional role in therapy resistance.

HOXB13-to-IL17BR Expression Ratio Is Related With Tumor Aggressiveness and Response to Tamoxifen of Recurrent Breast Cancer: A Retrospective Study

A HOXB13-to-IL17BR expression ratio was previously identified to predict clinical outcome of breast cancer patients treated with adjuvant tamoxifen. However, this ratio may predict a tumor's response to tamoxifen, its intrinsic aggressiveness, or both. We have measured the HOXB13 and IL17BR expression levels by real-time polymerase chain reaction in 1,252 primary breast tumor specimens. Expression levels were normalized to housekeeper gene levels and related to clinicopathologic factors for all patients. The primary objective of this study was to determine the relationship of a HOXB13-to-IL17BR ratio with tumor aggressiveness and/or with response to tamoxifen therapy in estrogen receptor (ER) -positive disease. We selected ER-positive tumors, and clinical end points for the HOXB13-to-IL17BR ratio were disease-free survival (DFS) in patients with primary breast cancer (N = 619) and progression-free survival (PFS) in patients with recurrent breast cancer treated with first-line tamoxifen monotherapy (N = 193). The odds ratio (OR) and hazard ratio (HR) and their 95% CI were calculated, and all P values were two-sided. The HOXB13-to-IL17BR ratio was significantly associated with DFS and PFS. In multivariate analysis, HOXB13-to-IL17BR ratio expression levels were associated with a shorter DFS for node-negative patients only. Corrected for traditional predictive factors, the dichotomized HOXB13-to-IL17BR ratio was the strongest predictor in multivariate analysis for a poor response to tamoxifen therapy (OR = 0.16; 95% CI, 0.06 to 0.45; P < .001) and a shorter PFS (HR = 2.97; 95% CI, 1.82 to 4.86; P < .001). High HOXB13-to-IL17BR ratio expression levels associate with both tumor aggressiveness and tamoxifen therapy failure.

Examining the Role of Culture-Specific Coping as a Predictor of Resilient Outcomes in African Americans From High-Risk Urban Communities

This investigation examined the role of culture-specific coping in relation to resilient outcomes in African Americans from high-risk urban communities. Participants (N = 385) were administered a survey questionnaire packet containing measures of culture-specific coping, traditional resilience factors (cognitive ability, social support, and familial factors), and resilient outcomes (physical, psychological, social, and environmental quality of life). Structural equation modeling was used to test the degree to which culture-specific coping would uniquely contribute to the prediction of quality of life above and beyond traditional predictive factors of resilience. Findings indicated that spiritual and collective coping were statistically significant predictors of quality of life outcomes above and beyond the traditional predictive factors. Overall, the findings indicated that both traditional and cultural factors were predictors of resilient outcomes (i.e., positive quality of life indicators) for African Americans.

How ADAM-9 and ADAM-11 Differentially From Estrogen Receptor Predict Response to Tamoxifen Treatment in Patients with Recurrent Breast Cancer: a Retrospective Study

To evaluate the predictive value of the disintegrin and metalloproteinases, ADAM-9, ADAM-10, ADAM-11, and ADAM-12, and of the matrix metalloproteinases, MMP-2 and MMP-9, in patients with recurrent breast cancer treated with tamoxifen. A retrospective study was done on 259 frozen specimens of estrogen receptor-positive primary breast carcinomas from patients who developed recurrent disease and were treated with tamoxifen as the first line of therapy. The expression levels of the biological factors were assessed by real-time quantitative reverse transcriptase PCR. Using log-transformed continuous variables, increasing levels of ADAM-9 [odds ratio (OR) = 1.41; P = 0.015] and decreasing levels of MMP-9 (OR, 0.81; P = 0.035) predicted favorable disease control independent from the traditional predictive factors. Furthermore, when tumors were dichotomized at the median level of 70% tumor cell nuclei, our univariate analysis showed particularly strong results for the group of 153 patients with primary tumors containing 30% or more stromal cells. Although estrogen receptor levels lost their predictive power for this group of patients, high levels of ADAM-9 (OR, 1.59; P = 0.007) and ADAM-11 (OR, 1.65; P = 0.001) were significantly associated with a higher efficacy of tamoxifen therapy. Our results show that especially for primary tumors containing stromal elements, the assessment of mRNA expression levels of ADAM-9 and ADAM-11 could be useful to identify patients with recurrent breast cancer who are likely to benefit or fail from tamoxifen therapy.

Can We Approach Zero Relapse in Breast Cancer?

Adjuvant hormonal therapy and adjuvant chemotherapy have contributed significantly to the falling rates of breast cancer mortality. The introduction of taxanes and aromatase inhibitors in the adjuvant setting represents recent important improvements. More recently, the demonstration of significant benefit in the adjuvant setting with novel molecular targeted therapies (such as trastuzumab [Herceptin; Genentech, Inc., South San Francisco, CA, http://www.gene.com]) is already beginning to have a substantial impact on the adjuvant treatment of patients with certain tumor characteristics (i.e., HER-2 positivity). Neoadjuvant treatment represents an approach that offers an intermediate end point (i.e., pathologic complete response) that can be used as a marker of therapeutic activity. Furthermore, the use of genomic profiling is starting to replace the traditional prognostic and predictive factors currently used to estimate risks for recurrence and response to particular adjuvant therapies. These recent developments have demonstrated that the notion of approaching zero relapse in breast cancer patients is now within our reach.

Molecular Classification of Tamoxifen-Resistant Breast Carcinomas by Gene Expression Profiling

To discover a set of markers predictive for the type of response to endocrine therapy with the antiestrogen tamoxifen using gene expression profiling. The study was performed on 112 estrogen receptor-positive primary breast carcinomas from patients with advanced disease and clearly defined types of response (ie, 52 patients with objective response v 60 patients with progressive disease) from start of first-line treatment with tamoxifen. Main clinical end points are the effects of therapy on tumor size and time until tumor progression (progression-free survival [PFS]). RNA isolated from tumor samples was amplified and hybridized to 18,000 human cDNA microarrays. Using a training set of 46 breast tumors, 81 genes were found to be differentially expressed (P < or = .05) between tamoxifen-responsive and -resistant tumors. These genes were involved in estrogen action, apoptosis, extracellular matrix formation, and immune response. From the 81 genes, a predictive signature of 44 genes was extracted and validated on an independent set of 66 tumors. This 44-gene signature is significantly superior (odds ratio, 3.16; 95% CI, 1.10 to 9.11; P = .03) to traditional predictive factors in univariate analysis and also significantly related with a longer PFS in univariate (hazard ratio, 0.54; 95% CI, 0.31 to 0.94; P = .03) as well as in multivariate analyses (P = .03). Our data show that gene expression profiling can be used to discriminate between breast cancer patients with progressive disease and objective response to tamoxifen. Additional studies are needed to confirm if the predictive signature might allow identification of individual patients who could benefit from other (adjuvant) endocrine therapies.

Urokinase-type plasminogen activator system in breast cancer: association with tamoxifen therapy in recurrent disease.

The prognostic value of components of the urokinase-type plasminogen activator (uPA) system, its receptor uPAR (CD87), and plasminogen activator inhibitors PAI-1 and PAI-2 is well established. We studied the predictive value of these proteolytic factors by evaluating the association of their tumor expression level and the efficacy of tamoxifen therapy in patients with recurrent breast cancer. The antigen levels of the four factors were determined by ELISA in cytosols prepared from estrogen receptor-positive primary breast tumors of 691 hormone-naive breast cancer patients with recurrent disease and treated with tamoxifen as first-line systemic therapy. High tumor levels of uPA (P < 0.001), uPAR (P < 0.01), and PAI-1 (P = 0.01) were associated with a lower efficacy of tamoxifen therapy. In the multivariable analysis, uPA (P < 0.001) provided additional information independent of the traditional predictive factors to predict benefit from tamoxifen therapy. High levels of uPA, uPAR, and PAI-1 predicted a shorter progression-free survival (PFS) on tamoxifen in an analysis of the first 9 months of therapy. However in the analysis during the total follow-up period, high PAI-2 levels (P = 0.01) showed a longer response to tamoxifen. In conclusion, uPA, uPAR, and PAI-1, components of the urokinase system, are predictive for the efficacy of tamoxifen therapy in patients treated for recurrent breast cancer. Knowledge of their tumor expression levels might be helpful for future individualized therapy protocols, including possible new-targeted therapies based on the interference in the urokinase system.

Elevated expression of polymorphonuclear leukocyte elastase in breast cancer tissue is associated with tamoxifen failure in patients with advanced disease.

Besides a variety of other proteases, polymorphonuclear leukocyte elastase (PMN-E) is also suggested to play a role in the processes of tumour cell invasion and metastasis. Yet, there is only limited data available on the relation between the tumour level of PMN-E and prognosis in patients with primary breast cancer, and no published information exists on its relation with the efficacy of response to systemic therapy in patients with advanced breast cancer. In the present study, we have measured with enzyme-linked immunosorbent assay the levels of total PMN-E in cytosolic extracts of 463 primary breast tumours, and have correlated their levels with the rate and duration of response on first-line tamoxifen therapy (387 patients) or chemotherapy (76 patients) in patients with locally advanced and/or distant metastatic breast cancer. Furthermore, the probabilities of progression-free survival and postrelapse survival were studied in relation to the tumour levels of PMN-E. Our results show that in logistic regression analysis for response to tamoxifen treatment in patients with advanced disease, high PMN-E tumour levels were associated with a poor rate of response compared with those with low PMN-E levels (odds ratio: OR, 0.40; 95% CI, 0.22–0.73; P=0.003). After correction for the contribution of the traditional predictive factors in multivariate analysis, the tumour PMN-E status was an independent predictor of response (P=0.01). Furthermore, a high tumour PMN-E level was related with a poor progression-free survival (P<0.001) and postrelapse survival (P=0.002) in a time-dependent analysis. In contrast, the tumour level of PMN-E was not significantly related with the efficacy of response to first-line chemotherapy in patients with advanced breast cancer. Our present results suggest that PMN-E is an independent predictive marker for the efficacy of tamoxifen treatment in patients with advanced breast cancer.