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C K Osborne

Publications and source records attributed to C K Osborne.

At least 37 records · Page 2Linked to original sources
PubMed2000

Prediction of clinical outcome from primary tamoxifen by expression of biologic markers in breast cancer patients.

The aim of this study was to evaluate pretreatment clinical features and biological markers together with changes in these factors as predictors of response and relapse in patients receiving tamoxifen for primary breast cancer. Fine-needle aspiration cytology of the primary breast cancer was performed before tamoxifen treatment in 54 patients and repeated after therapy on day 14, day 60, or on both days in a subset of 35 patients. These samples were evaluated for estrogen receptor (ER), progesterone receptor (PgR), Ki67, S-phase fraction and ploidy. The overall response to tamoxifen was 57% (31 of 54 patients). Pretreatment ER and PgR significantly predicted for response by univariate analysis (P < 0.0001 and P < 0.003, respectively). By multivariate analysis, ER expression was the only independent predictor of response, and it was associated with 27 times the likelihood of response (95% confidence interval, 6-136). Increase in PgR and decrease in Ki67 on day 14 significantly predicted for response to tamoxifen (P < 0.03 and P < 0.04, respectively). Lack of ER, clinical node-positive disease, and failure to decrease Ki67 on day 14 were significantly associated with increased risk of relapse (P < 0.05). By multivariate analysis, ER expression was the only independent predictor of relapse (P < 0.005). Pretreatment and early changes in molecular marker expression may assist in the prediction of response and clinical outcome in primary breast cancer patients receiving tamoxifen.

Aged↗
PubMed2000

HET/SAF-B overexpression causes growth arrest and multinuclearity and is associated with aneuploidy in human breast cancer.

HET/SAF-B was originally cloned as a nuclear matrix protein that bound to matrix attachment regions and as a transcriptional repressor of the small heat shock protein hsp27. In addition, we have found recently that HET/SAF-B is also a corepressor of estrogen receptor activity. Estrogen receptor has a very well-described role in breast cancer, and aberrant expression of nuclear matrix and heat shock proteins has also been implicated in breast tumorigenesis. Therefore, we asked whether HET/SAF-B itself could be important in breast cancer. Toward this goal we examined its expression in breast cancer cell lines and asked whether HET/SAF-B can affect breast cancer cell proliferation. Finally, we studied HET/SAF-B expression in clinical breast cancer samples. HET/SAF-B protein and mRNA were detected at varying levels in all of the eight breast cancer cell lines examined. Using a number of different approaches to modulate the level of HET/SAF-B protein in the cell, we found that HET/SAF-B levels are inversely correlated with cell proliferation. In addition,transfection of HET/SAF-B fused to the green fluorescent protein led to the formation of multinucleated cells not observed in cells transfected with green fluorescent protein alone, suggesting that this effect is a direct result of HET/SAF-B overexpression. Western blot analysis of HET/SAF-B in 61 human breast tumors revealed widely varying levels of HET/SAF-B expression, with some tumors (16%) lacking any detectable HET/SAF-B. Statistical analysis showed that high HET/SAF-B expression in these tumors was associated with low S-phase fraction and with aneuploidy, consistent with our results from transfection experiments in tissue culture cells. We conclude that HET/SAF-B plays an important role in breast cancer, and we discuss possible mechanisms of the involvement of HET/SAF-B in cell proliferation and division.

3T3 Cells↗
PubMed1999

Loss of heterozygosity at D14S62 and metastatic potential of breast cancer.

BACKGROUND: In breast cancer progression, the prevalence of damage at specific genetic loci often increases with the stage of the lesion (i.e., from noninvasive to invasive to metastatic). By use of genetic markers and analysis of allelic imbalances (loss of heterozygosity [LOH]) to compare DNA samples from paired normal and breast tumor tissues, we examined whether specific genetic changes in primary breast cancers can serve as biomarkers of metastatic potential. METHODS: DNA samples from 76 patients with primary breast cancer (42 with axillary lymph node-negative disease and 34 with axillary lymph node-positive disease) were genotyped with four genetic markers spanning chromosome 14q31-q32. The intensity ratios of the two genetic alleles in normal-tumor DNA pairs were examined in genetically informative individuals. LOH was scored when the tumor allele intensity ratio (tumor allele 1/tumor allele 2) divided by the normal allele intensity ratio (normal allele 1/normal allele 2) was either less than 0.71 (tumor allele 1 LOH) or greater than 1. 4 (tumor allele 2 LOH). RESULTS/CONCLUSIONS: Contrary to our expectations, we found statistically significantly more LOH events at markers D14S62 (two-sided P =.001) and D14S51 (two-sided P =.02) in primary breast cancers from patients with lymph node-negative disease versus lymph node-positive disease, suggesting the presence of a gene in this region that affects metastatic potential. Analysis of small interstitial or terminal deletions in the tumors of six especially informative patients with lymph node-negative disease places the putative metastasis-related gene in a 1490-kilobase region near D14S62. IMPLICATIONS: LOH in the D14S62 region may impede the process of metastasis. Therefore, the D14S62 region LOH profile may have prognostic implications, and the isolation of the metastasis-related gene(s) in this region may lead to better diagnosis and treatment of breast cancer.

Biomarkers, Tumor↗
PubMed1999

Binding of CtIP to the BRCT repeats of BRCA1 involved in the transcription regulation of p21 is disrupted upon DNA damage.

Mutations in BRCA1 are responsible for nearly all of the hereditary ovarian and breast cancers, and about half of those in breast cancer-only kindreds. The ability of BRCA1 to transactivate the p21 promoter can be inactivated by mutation of the conserved BRCA1 C-terminal (BRCT) repeats. To explore the mechanisms of this BRCA1 function, the BRCT repeats were used as bait in a yeast two-hybrid screen. A known protein, CtIP, a co-repressor with CtBP, was found. CtIP interacts specifically with the BRCT repeats of BRCA1, both in vitro and in vivo, and tumor-derived mutations in this region abolished these interactions. The association of BRCA1 with CtIP was also abrogated in cells treated with DNA-damaging agents including UV, gamma-irradiation, and adriamycin, a response correlated with BRCA1 phosphorylation. The transactivation of the p21 promoter by BRCA1 was diminished by expression of exogenous CtIP and CtBP. These results suggest that the binding of the BRCT repeats of BRCA1 to CtIP/CtBP is critical in mediating transcriptional regulation of p21 in response to DNA damage.

BRCA1 Protein↗
PubMed1999

Statistical analysis of array expression data as applied to the problem of tamoxifen resistance.

BACKGROUND: Although the emerging complementary DNA (cDNA) array technology holds great promise to discern complex patterns of gene expression, its novelty means that there are no well-established standards to guide analysis and interpretation of the data that it produces. We have used preliminary data generated with the CLONTECH Atlas human cDNA array to develop a practical approach to the statistical analysis of these data by studying changes in gene expression during the development of acquired tamoxifen resistance in breast cancer. METHODS: For hybridization to the array, we prepared RNA from MCF-7 human breast cell tumors, isolated from our athymic nude mouse xenograft model of acquired tamoxifen resistance during estrogen-stimulated, tamoxifen-sensitive, and tamoxifen-resistant growth. Principal components analysis was used to identify genes with altered expression. RESULTS AND CONCLUSIONS: Principal components analysis yielded three principal components that are interpreted as 1) the average level of gene expression, 2) the difference between estrogen-stimulated gene expression and the average of tamoxifen-sensitive and tamoxifen-resistant gene expression, and 3) the difference between tamoxifen-sensitive and tamoxifen-resistant gene expression. A bivariate (second and third principal components) 99% prediction region was used to identify outlier genes that exhibit altered expression. Two representative outlier genes, erk-2 and HSF-1 (heat shock transcription factor-1), were chosen for confirmatory study, and their predicted relative expression levels were confirmed in western blot analysis, suggesting that semiquantitative estimates are possible with array technology. IMPLICATIONS: Principal components analysis provides a useful and practical method to analyze gene expression data from a cDNA array. The method can identify broad patterns of expression alteration and, based on a small simulation study, will likely provide reasonable power to detect moderate-sized alterations in clinically relevant genes.

Animals↗
PubMed1999

Biologic markers as predictors of clinical outcome from systemic therapy for primary operable breast cancer.

PURPOSE: To determine whether pretreatment clinical features and molecular markers, together with changes in these factors, can predict treatment response and survival in patients with primary operable breast cancer who receive neoadjuvant therapy. PATIENTS AND METHODS: Mitoxantrone, methotrexate (with or without mitomycin), and tamoxifen chemoendocrine therapy was administered to 158 patients before surgery. Clinical response was assessed after four cycles of treatment. Fine-needle aspiration cytology for estrogen receptor (ER), progesterone receptor (PgR), c-erbB-2, p53, bcl-2, Ki67, S-phase fraction (SPF), and ploidy were performed pretreatment and repeated on day 10 or day 21 after the first cycle of treatment. RESULTS: Good clinical response (GCR, defined as complete response or minimal residual disease) was achieved in 31% of patients (49 of 158). Tumor size, nodal disease, response, ER, PgR, c-erbB-2, p53, bcl-2, Ki67, SPF, and ploidy were analyzed as predictors of survival. By univariate analysis, node-positive disease (P =.05), lack of ER (P <.05) and PgR (P <.05), and failure to attain GCR (P =.008) were associated with a significantly increased risk of relapse. A significantly increased risk of death was associated with node-positive disease (P =.02), lack of ER expression (P =.04), and failure to attain GCR. By multivariate analysis, GCR was an independent predictor for survival (P =.05). ER expression (P =.03), absence of c-erbB-2 (P =.03), and a decrease in Ki67 on day 10 or day 21 of the first cycle (P <.05) significantly predicted for subsequent GCR. CONCLUSION: Molecular markers may be used to predict the likelihood of achieving GCR, which seems to be a valid surrogate marker for survival.

Adult↗
PubMed1999

Tumor characteristics and clinical outcome of tubular and mucinous breast carcinomas.

PURPOSE: To comprehensively characterize the clinical and biologic features of tubular and mucinous carcinomas in a large cohort of patients and to relate this to clinical outcome and management. PATIENTS AND METHODS: The clinical and biologic features of 444 patients with tubular and 1,221 patients with mucinous carcinomas were compared with those of 43,587 patients with infiltrating ductal carcinoma, not otherwise specified (NOS). Disease-free survival (DFS) and overall survival (OS) for patients with tubular and mucinous carcinomas were compared with those of patients with NOS carcinomas and with age-matched sets from the general population. RESULTS: Tubular and mucinous carcinomas were more likely to occur in older patients, be smaller in size (tubular only), have substantially less nodal involvement, be estrogen receptor- and progesterone receptor-positive, have a lower S-phase fraction, be diploid, and be c-erbB-2- and epidermal growth factor receptor-negative compared with NOS carcinomas. Axillary node involvement was a poor prognostic feature in mucinous but not tubular carcinomas. Mucinous carcinomas < or = 1 cm had a < or = 5% incidence of node involvement. The 5-year DFS and OS were 94% and 88% for tubular, 90% and 80% for mucinous, and 80% and 77% for NOS carcinoma, respectively (P < .001 for differences among all three types for both DFS and OS). The 5-year OS of females from the general population age-matched to the patients with tubular and mucinous carcinomas was 89% and 82%, respectively, which is not different from the OS of patients with tubular or mucinous carcinomas. CONCLUSION: The biologic phenotype of tubular and mucinous carcinomas is quite favorable. Consistent with this observation, the survival of patients with tubular and mucinous carcinomas is similar to that of the general population. Systemic adjuvant therapy and node dissection may be avoided in many patients with these special types of carcinoma.

Adenocarcinoma↗
PubMed1999

Estrogen receptor status by immunohistochemistry is superior to the ligand-binding assay for predicting response to adjuvant endocrine therapy in breast cancer.

PURPOSE: Immunohistochemistry (IHC) is a newer technique for assessing the estrogen receptor (ER) status of breast cancers, with the potential to overcome many of the shortcomings associated with the traditional ligand-binding assay (LBA). The purpose of this study was to evaluate the ability of ER status determination by IHC, compared with LBA, to predict clinical outcome-especially response to adjuvant endocrine therapy-in a large number of patients with long-term clinical follow-up. PATIENTS AND METHODS: ER status was evaluated in 1,982 primary breast cancers by IHC on formalin-fixed paraffin-embedded tissue sections, using antibody 6F11 and standard methodology. Slides were scored on a scale representing the estimated proportion and intensity of positive-staining tumor cells (range, 0 to 8). Results were compared with ER values obtained by the LBA in the same tumors and to clinical outcome. RESULTS: An IHC score of greater than 2 (corresponding to as few as 1% to 10% weakly positive cells) was used to define ER positivity on the basis of a univariate cut-point analysis of all possible scores and disease-free survival (DFS) in patients receiving any adjuvant endocrine therapy. Using this definition, 71% of all tumors were determined to be ER-positive by IHC, and the level of agreement with the LBA was 86%. In multivariate analyses of patients receiving adjuvant endocrine therapy alone, ER status determined by IHC was better than that determined by the LBA at predicting improved DFS (hazard ratios/P = 0.474/.0008 and 0.707/.3214, respectively) and equivalent at predicting overall survival (0.379/.0001 and 0.381/.0003, respectively). CONCLUSION: IHC is superior to the LBA for assessing ER status in primary breast cancer because it is easier, safer, and less expensive, and has an equivalent or better ability to predict response to adjuvant endocrine therapy.

Adult↗
PubMed1999

Significance of axillary lymph node metastasis in primary breast cancer.

PURPOSE: Axillary lymph node status is the single most important prognostic variable in the management of patients with primary breast cancer. Yet, it is not known whether metastasis to the axillary nodes is simply a time-dependent variable or also a marker for a more aggressive tumor phenotype. The purpose of this study was to determine whether nodal status at initial diagnosis predicts outcome after relapse and therefore also serves as a marker of breast cancer phenotype. PATIENTS AND METHODS: Survival experience after first relapse in 1,696 primary breast cancer cases was analyzed using Cox proportional hazards regression. The following explanatory variables and their first-order interactions were considered: number of axillary lymph nodes involved (zero v one to three v four or more), hormone receptor status (any estrogen receptor [ER] negativity v ER negativity/progesterone receptor positivity v other ER positivity), primary tumor size (< 2 cm v 2 to 5 cm v > 5 cm), site of relapse (locoregional v distant), disease-free interval (< 1.5 years v 1.5 to 3 years v > 3 years), adjuvant endocrine therapy (none v any), adjuvant chemotherapy (none v any), and menopausal status (pre-, peri-, or postmenopausal). RESULTS: Axillary lymph node status, site of relapse, and hormone receptor status were all highly significant as main effects in the model. After adjustment for other variables, disease-free interval alone was only modestly significant but interacted with nodal status. After disease-free interval, hormone receptor status, and site of relapse were accounted for, survival after relapse was poorer in node-positive cases, when compared with node-negative cases. The hazard ratios for patients with one to three and four or more involved nodes were 1.2 (95% confidence interval [CI], 0.8 to 1.9) and 2.5 (95% CI, 1.8 to 3.4), respectively. CONCLUSION: Patients with four or more involved nodes at initial diagnosis have a significantly worse outcome after relapse than node-negative cases, regardless of the duration of the disease-free interval. We conclude that nodal metastasis is not only a marker of diagnosis at a later point in the natural history of breast cancer but also a marker of an aggressive phenotype.

Axilla↗
PubMed1999

Enhancement of insulin-like growth factor signaling in human breast cancer: estrogen regulation of insulin receptor substrate-1 expression in vitro and in vivo.

Cross-talk between insulin-like growth factor (IGF)- and estrogen receptor (ER)-signaling pathways results in synergistic growth. We show here that estrogen enhances IGF signaling by inducing expression of three key IGF-regulatory molecules, the type 1 IGF receptor (IGFR1) and its downstream signaling molecules, insulin receptor substrate (IRS)-1 and IRS-2. Estrogen induction of IGFR1 and IRS expression resulted in enhanced tyrosine phosphorylation of IRS-1 after IGF-I stimulation, followed by enhanced mitogen-activated protein kinase activation. To examine whether these pathways were similarly activated in vivo, we examined MCF-7 cells grown as xenografts in athymic mice. IRS-1 was expressed at high levels in estrogen-dependent growth of MCF-7 xenografts, but withdrawal of estrogen, which decreased tumor growth, resulted in a dramatic decrease in IRS-1 expression. Finally, we have shown that high IRS-1 expression is an indicator of early disease recurrence in ER-positive human primary breast tumors. Taken together, these data not only reinforce the concept of cross-talk between IGF- and ER-signaling pathways, but indicate that IGF molecules may be critical regulators of estrogen-mediated growth and breast cancer pathogenesis.

Animals↗
PubMed1999

Aromatase inhibitors in relation to other forms of endocrine therapy for breast cancer.

Most endocrine therapies for breast cancer inhibit tumor growth by depriving the cell of estrogen or by blocking its receptor. However, some drugs, such as tamoxifen, can bind to the estrogen receptor (ER) and have both estrogenic and antiestrogenic effects, depending on the tissue, cell, or promoter context. These mixed properties may be explained by new information on ER function at the molecular level. Whether a synthetic drug acts as an estrogen or antiestrogen on a specific gene may be dictated by the particular ensemble of ER subtype, receptor interacting proteins, other transcription factors, or specific elements within the promoter of estrogen-regulated genes. Alterations in these other factors may also play a role in resistance to hormonal therapies. Aromatase inhibitors, like ovarian ablation, inhibit growth by lowering the estrogen concentration in blood or in the tumor tissue itself. Aromatase inhibitors are effective even in postmenopausal women with low estrogen concentrations - probably because of the ability of the tumor to become hypersensitive to estrogen after prolonged estrogen deprivation. Given that the ER itself is the prime target for endocrine manipulation, the ideal endocrine therapy may be one that reduces or eliminates ER from the tumor cell. Pure steroidal antiestrogens are then of great interest because, not only do they inhibit ER-induced transactivation of estrogen regulated genes, they also induce ER degradation. Additional clinical trials are necessary to identify the optimal endocrine therapy and optimal sequence of available therapies.

Antineoplastic Agents↗
PubMed1998

Analysis of loss of heterozygosity in 399 premalignant breast lesions at 15 genetic loci.

BACKGROUND: Usual ductal hyperplasia (UDH), atypical ductal hyperplasia (ADH), and ductal carcinoma in situ (DCIS) are risk factors for invasive breast cancer (IBC), suggesting that these lesions may be direct precursors of IBC. To identify genetic changes that may be important in the early development of precursor lesions and their progression to malignant or invasive disease, we examined 399 putative precursors (211 UDH, 51 ADH, 81 non-comedo DCIS, and 56 comedo DCIS) for loss of heterozygosity (LOH) at 15 polymorphic genetic loci known to exhibit high rates of loss in IBC. We also assessed the sharing of LOH by putative precursors and synchronous cancers. METHODS: The polymerase chain reaction was used to analyze DNA from microdissected archival specimens. RESULTS AND CONCLUSIONS: In hyperplasias from noncancerous breasts (i.e., without DCIS and/or IBC in analyses of hyperplasias), LOH at any given locus was rare (range, 0%-15%), although 37% of UDH and 42% of ADH lesions showed loss for at least one locus, suggesting that the development of hyperplasias can involve many different tumor suppressor genes. In DCIS from noncancerous breasts (i.e., without IBC in analyses of DCIS), LOH was common, with 70% of noncomedo lesions and 79% of comedo lesions showing at least one loss. In DCIS, substantial rates of loss (up to 37%) were observed at loci on chromosomes 16q, 17p, and 17q, suggesting that inactivated tumor suppressor genes in these regions may be important in the development of noninvasive breast cancer. When DCIS lesions from cancerous and noncancerous breasts were compared, substantially more LOH was observed in the cancerous breasts at a few loci (on chromosomes 2p, 11p, and 17q), suggesting that genetic alterations in these regions may be important in the progression to invasive disease. Among specimens harvested from cancerous breasts, 37% of UDH, 45% of ADH, 77% of noncomedo DCIS, and 80% of comedo DCIS lesions shared LOH with synchronous cancers at one locus or more, supporting the idea that the putative precursors and the cancers are genetically related.

Breast Diseases↗
PubMed1998

bcl-2 and apoptosis in lymph node positive breast carcinoma.

BACKGROUND: Because bcl-2 can block apoptosis in vitro, and because lower levels of apoptosis might lead to malignant cell accumulation and therefore to a more aggressive clinical course, the authors tested the hypothesis that high bcl-2 and low apoptosis would result in a worse prognosis for breast carcinoma patients. METHODS: Primary breast tumor specimens from 979 patients with positive axillary lymph nodes were evaluated for bcl-2 protein expression by immunohistochemistry (IHC). Apoptosis was evaluated by using IHC to detect 3' DNA fragments end-labeled with biotinylated uridine. Results were analyzed with respect to patient characteristics, prognostic factors, and clinical outcome. Median follow-up was 61 months. RESULTS: High bcl-2 expression was significantly associated with a number of favorable prognostic factors, including a lower number of positive lymph nodes, absence of p53 protein accumulation, estrogen receptor (ER) and progesterone receptor (PR) positivity, diploidy, and a lower proliferative rate. However, although bcl-2 is generally considered a negative regulator of apoptosis, in these tumors there was no significant association between bcl-2 and apoptosis. Patients with high bcl-2 expression had significantly improved disease free survival (DFS) (P < 0.0001) and overall survival (OS) (P < 0.0001). In a multivariate analysis, bcl-2 expression was independently associated with better DFS (P = 0.004). Regarding apoptosis, the presence of > or = 1% apoptotic cells was significantly associated with a greater number of positive lymph nodes, p53 protein expression, ER and PR negativity, aneuploidy, and a higher proliferation rate, although there was no significant association with a worse clinical outcome when this dichotomized cutoff was used. CONCLUSIONS: For lymph node positive breast carcinoma patients, high bcl-2 expression is associated with a number of good prognostic factors and is independently associated with better clinical outcome. Apoptosis is associated with a number of poor prognostic factors but not with a significantly worse outcome.

Apoptosis↗
PubMed1998

Diverse signaling pathways modulate nuclear receptor recruitment of N-CoR and SMRT complexes.

Several lines of evidence indicate that the nuclear receptor corepressor (N-CoR) complex imposes ligand dependence on transcriptional activation by the retinoic acid receptor and mediates the inhibitory effects of estrogen receptor antagonists, such as tamoxifen, suppressing a constitutive N-terminal, Creb-binding protein/coactivator complex-dependent activation domain. Functional interactions between specific receptors and N-CoR or SMRT corepressor complexes are regulated, positively or negatively, by diverse signal transduction pathways. Decreased levels of N-CoR correlate with the acquisition of tamoxifen resistance in a mouse model system for human breast cancer. Our data suggest that N-CoR- and SMRT-containing complexes act as rate-limiting components in the actions of specific nuclear receptors, and that their actions are regulated by multiple signal transduction pathways.

Animals↗
PubMed1998

Expanded phase II trial of paclitaxel in metastatic breast cancer: a Southwest Oncology Group study.

BACKGROUND: The study was designed to evaluate the efficacy of paclitaxel in metastatic breast cancer patients. The design was motivated by a report from FDA and NCI staff proposing assessment of pre- and post-treatment symptoms as a means of evaluating treatment effectiveness [1]. METHODS: Patients with symptomatic and/or measurable metastatic breast cancer with prior treatment received paclitaxel 210 mg/m2 as a 3 hour infusion every three weeks until toxicity or progression. A unique endpoint was subjective symptomatic response, defined as an improvement in the Symptom Distress Scale score by > or = 3 points at two successive evaluations before treatment failure. Patients were also evaluated for objective response and toxicity. RESULTS: Of 135 patients registered, 123 were eligible and treated. The subjective symptomatic response rate for 93 symptomatic patients who completed forms was 40%, 95% confidence interval 29-51%. The objective response rate in 77 patients with measurable disease was 19%, 95% confidence interval 11-30%. In patients with both measurable and symptomatic disease, 37% had symptomatic and 13% had objective responses. Median times to treatment failure and death were 4 and 11 months, respectively. Toxicity was greater than anticipated: 12% discontinued treatment due to toxicity, 29% developed at least one Grade 3 neuromuscular toxicity, and two patients died of sepsis while neutropenic. CONCLUSION: Paclitaxel by 3 hour infusion at a dose of 210 mg/m2 produced excessive neurotoxicity in patients with previously treated metastatic breast cancer. Both sustained subjective symptom reduction and objective responses were demonstrated, but dose reduction for routine practice is recommended.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Steroid hormone receptors in breast cancer management.

Estrogen and progesterone receptors (ER and PR) have now been studied in clinical breast cancer for more than 20 years. Positive receptor status correlates with favorable prognostic features including a lower rate of cell proliferation and histologic evidence of tumor differentiation. During the first several years after diagnosis, patients with ER-positive tumors tend to have a lower recurrence rate; however, this is balanced by a higher recurrence rate in subsequent years so that the overall prognostic significance of receptor status is modest. ER and PR have their greatest utility in predicting response to hormonal therapy, both in the adjuvant setting and for advanced disease. When the assay is done properly and cut-offs for ER-negativity and positivity are defined by clinical studies of patients treated with endocrine therapy, receptor status is very helpful in identifying groups of patients who are very unlikely to benefit from hormonal therapy. Tumors that express both ER and PR have the greatest benefit from hormonal therapy, but those containing only ER or only PR still have significant responses. Two types of estrogen receptors, ERalpha and ERbeta, have now been identified. Although there is considerable homology between these receptor forms, they appear to have important structural and functional differences that may be important for tissue and promoter-specific regulation of gene expression. These receptor forms, as well as ER variants and mutants, may also contribute to hormonal sensitivity and resistance. PR also exists in two forms, PRA and PRB. PRA appears to have repressor functions on both PRB and ERalpha, and the ratio of PRA to PRB in clinical breast tumors needs to be studied for its possible clinical relevance. Expression of receptor-interacting proteins can also modulate ER transcriptional activity, and these too need additional study to determine if they are markers of hormonal sensitivity or resistance. In summary, ER and PR status are important biomarkers that help physicians individualize therapy.

Biomarkers, Tumor↗
PubMed1998

Time-dependence of hazard ratios for prognostic factors in primary breast cancer.

Some prognostic factors, such as steroid receptors, appear strongly related to outcome in early studies with short follow-up, but as follow-up matures the relationships appear to weaken. We investigated this phenomenon for several factors (tumor size, axillary lymph nodes, S-phase fraction, estrogen receptor (ER) status, and adjuvant therapy) in a large sample of breast cancer cases (N=2,873) with up to 17 years of follow-up for disease-free survival (DFS). Subjects in the study were identified from patients who had hormone receptor assays performed in our laboratory. Analysis of DFS included fitting a multivariate Cox proportional hazards model, testing for nonproportionality, and examining diagnostic plots. The assumption of proportional hazards was violated for several factors including ER, tumor size, and S-phase fraction. For ER, the hazard ratio was initially less than 1.0, indicating a good effect on prognosis, but increased at later times to values greater than 1.0, indicating a bad effect on prognosis. In contrast, the hazard ratios for tumor size and S-phase were initially high and decreased asymptotically toward 1.0 over time. Analysis of p53 expression in a subset of cases yielded qualitatively similar results. We conclude that several standard prognostic factors (ER, tumor size, S-phase fraction) and possibly other investigational factors have important but nonproportional effects on hazard. It is likely that violation of proportional hazards is common and not limited to breast cancer. Failure to recognize violations of proportional hazards can lead to both over- and under-estimation of the effects of important prognostic factors.

Adult↗