Biomedical subjects

Matthew J Ellis

Publications and source records attributed to Matthew J Ellis.

27 records · Page 2Linked to original sources

PubMed2004

Importance of correlative science in advancing hormonal therapy and a new clinical paradigm for neoadjuvant therapy.

Improvement in endocrine therapy for estrogen receptor (ER)-positive breast cancer will require prevention or modulation of resistance, based on identification and targeting of the responsible molecular mechanisms. Our approach to this problem has been to focus on neoadjuvant endocrine treatment because that permits comparative evaluation of pretreatment tumor biopsies and surgical tumor specimens. We have begun utilizing this clinical paradigm by exploring semiquantitative changes in the expression of molecular markers within tumors treated with either tamoxifen or the aromatase inhibitor letrozole in a randomized trial. This investigation is beginning to elucidate the influence of growth factor pathways that interact with the ER, especially HER1 (epidermal growth factor receptor [EGFR]) and HER2. The results indicate that the distinct mechanisms by which tamoxifen and letrozole inhibit ER signaling may produce quite marked differences in clinical and biomarker outcomes in the subset of tumors that coexpress HER1 and/or HER2 with ER, favoring estrogen-deprivation therapy. Ongoing investigations are examining gene expression profile changes associated with neoadjuvant endocrine therapy, as well as inhibitors of growth factor signaling that may modulate tamoxifen resistance.

Antineoplastic Agents, Hormonal↗

PubMed2004

Successful targeting of ErbB2 receptors-is PTEN the key?

Women with ErbB2-positive breast cancer have a poor prognosis, and frequently, chemotherapy treatment is ineffective. The ErbB2-targeted antibody trastuzumab improves survival when given with chemotherapy to patients with ErbB2-overexpressing metastatic disease, but treatment is not curative, and primary resistance is common. Postulated mechanisms of action for trastuzumab include immune-mediated cytotoxicity and receptor downmodulation. A study in this issue of Cancer Cell suggests that trastuzumab causes rapid activation of the PTEN lipid phosphatase, which in turn downregulates the phosphatidylinositol 3'-kinase (PI3K) pathway. Resistance to trastuzumab occurs when PTEN function is lost, suggesting that PTEN activation is a critical component of the therapeutic effect.

Antibodies, Monoclonal↗

PubMed2004

Neoadjuvant endocrine therapy for breast cancer: an overlooked option?

For many oncologists, neoadjuvant treatment for breast cancer is synonymous with preoperative cytotoxic chemotherapy, regardless of tumor characteristics. Preoperative therapy with an endocrine agent is generally considered suitable only for the frail elderly or the medically unfit. However, favorable information regarding third-generation aromatase inhibitors in the treatment of all stages of breast cancer prompts a reconsideration of this bias. In light of the fact that neoadjuvant therapy with aromatase inhibitors is restricted to postmenopausal women with strongly estrogen-receptor-positive tumors, the assumption that neoadjuvant combination chemotherapy is more efficacious than a third-generation aromatase inhibitor can be reasonably questioned. It is particularly remarkable that the outcome of a comparison of adjuvant tamoxifen vs anastrozole (Arimidex)--the Arimidex, Tamoxifen Alone or in Combination (ATAC) trial--in more than 6,000 patients was predicted by a neoadjuvant trial that showed an efficacy advantage for a third-generation aromatase inhibitor (letrozole [Femara]) compared to tamoxifen in a sample of 337 patients after only 4 months of treatment. The potential of the neoadjuvant setting in efforts to identify new biologic agents that could build on the effectiveness of adjuvant aromatase inhibitors is therefore beginning to be appreciated. Finally, neoadjuvant therapy with an aromatase inhibitor could be considered a sensitivity test of endocrine therapy that might be incorporated into strategies to individualize treatment according to response. For this possibility to be realized, however, a better understanding of the relationship between surrogates from the neoadjuvant setting and the long-term outcome of adjuvant aromatase inhibitor therapy will have to be established through practice-setting clinical trials.

Antineoplastic Agents, Hormonal↗

PubMed2003

Letrozole inhibits tumor proliferation more effectively than tamoxifen independent of HER1/2 expression status.

BACKGROUND: The biological basis for the superior efficacy of neoadjuvant letrozole versus tamoxifen for postmenopausal women with estrogen receptor (ER)-positive locally advanced breast cancer was investigated by analyzing tumor proliferation and expression of estrogen-regulated genes before and after the initiation of therapy. METHODS: Tumor samples were obtained at baseline and at the end of treatment from 185 patients participating in a double blind randomized Phase III study of neoadjuvant endocrine therapy. These paired specimens were simultaneously analyzed for Ki67, ER, progesterone receptor (PgR), trefoil factor 1 (PS2), HER1 (epidermal growth factor receptor), and HER2 (ErbB2 or neu) by semiquantitative immunohistochemistry. RESULTS: The treatment-induced reduction in geometric mean Ki67 was significantly greater with letrozole (87%) than tamoxifen (75%; analysis of covariance P = 0.0009). Differences in the average Ki67 reduction were particularly marked for ER-positive tumors that overexpressed HER1 and/or HER2 (88 versus 45%, respectively; P = 0.0018). Twenty-three of 92 tumors (25%) on tamoxifen and 14 of 93 on letrozole (15%) showed a paradoxical increase in Ki67 with treatment, and the majority of these cases was HER1/2 negative. Letrozole, but not tamoxifen, significantly reduced expression of the estrogen-regulated proteins PgR and trefoil factor 1, regardless of HER1/2 status (P < 0.0001). ER down-regulation occurred with both agents, although levels decreased more with tamoxifen (P < 0.0001). CONCLUSION: Letrozole inhibited tumor proliferation to a greater extent than tamoxifen. The molecular basis for this advantage appears complex but includes possible tamoxifen agonist effects on the cell cycle in both HER1/2+ and HER1/2- tumors. A pattern of continued proliferation despite appropriate down-regulation of PgR expression with estrogen deprivation or tamoxifen was also documented. This observation suggests the estrogenic regulation of proliferation and PgR expression may be dissociated in endocrine therapy resistant cells.

Antineoplastic Agents, Hormonal↗

PubMed2003

Neoadjuvant comparisons of aromatase inhibitors and tamoxifen: pretreatment determinants of response and on-treatment effect.

Adjuvant endocrine therapy reduces the risk of relapse and death from early stage hormone receptor positive breast cancer. However, tamoxifen is only partially effective because of the development of tumor resistance. Aromatase inhibitors (letrozole, anastrozole and exemestane) are also prone to the development of resistance but the pharmacologic action (estrogen deprivation) is distinct and so different mechanisms may be responsible. The problem of endocrine resistance can be directly studied in patients by examining the relationship between predictive tumor biomarkers and clinical outcome. In an example of a prospectively planned biomarker study, tumor samples were examined from a randomized trial of neoadjuvant endocrine treatment in which letrozole proved more effective than tamoxifen in terms of the rate of breast conservation and tumor regression. Interestingly letrozole was more effective at all levels of ER expression and was particularly more efficacious than tamoxifen for tumors that expressed HER1 and/or HER2 (with ER). This suggests that HER1/2 predicts primary tamoxifen resistance and relative sensitivity to potent estrogen deprivation, perhaps because HER1/2 signaling promotes the partial agonist effects of tamoxifen. A Phase 2 study of neoadjuvant letrozole is now underway to focus on gene expression profiling as a mechanism to further investigate the transcriptional programs that underlie resistance and sensitivity to estrogen deprivation. Expression profiles taken at baseline and after 1 month of therapy reveal dramatic reductions in the expression from genes responsible for DNA replication and synthesis, cell cycle progression, suppression of apoptosis and tissue invasion. When enough profiles have been generated it should be possible to detect complex interaction patterns that correctly reclassify ER+ disease into treatment responsive and resistant categories with high probability.

Aromatase Inhibitors↗

PubMed2003

Role of biologic markers in patient selection and application to disease prevention.

Aromatase inhibitors (AIs) are now under investigation for the treatment of early stage breast cancer and for disease prevention as alternatives to standard treatment with tamoxifen. Currently identified genetic risk factors of breast cancer include BRCA-1/BRCA-2 mutations, ATM mutations, and history of high estrogen levels, as evidenced by plasma analyses and/or dense bones. To date, estrogen receptor (ER) and progesterone receptor (PgR) status has predictive value for determining response to therapy in patients with hormone receptor-positive breast cancer (ER+ and/or PgR+ tumors). Recent studies have shown AIs to be safer and more effective than tamoxifen in postmenopausal women with advanced disease. Some data suggest that letrozole may be a more effective treatment than tamoxifen for patients with ER+ and/or PgR+ early breast cancers expressing ErbB-1 and/or ErbB-2. Changes in cell proliferation markers (e.g., S-phase fraction and Ki67 antigen), plasma lipid levels, and the bone resorption marker C-terminal peptide are biomarkers that have been evaluated for preventive and prognostic value in breast cancer patients and normal volunteers. Results from biomarker screens can be used to define inclusion criteria for clinical trials and eventually to individualize treatment. Gene expression profiling (microarray analysis), i.e., genomic and proteomic studies, will probably advance the discovery of new biomarkers for breast cancer prevention and treatment.

Antineoplastic Agents↗

PubMed2003

Breast cancer gene expression analysis--the case for dynamic profiling.

Cancer is a complicated disease with each individual tumor exhibiting to a variable degree a set of overlapping phenotypes that include abnormal proliferation and cell survival, genetic instability, tissue invasion, metastasis and angiogenesis. Each of these pathophysiological functions requires abnormal signaling that fails to respect the normal restraints imposed on healthy cells through homeostatic regulation. Understanding of deregulated gene expression is therefore an essential goal for cancer research because unraveling this problem will provide insights into the fundamental nature of cancer as well as provide opportunities for therapeutic intervention. Gene expression profiling is a remarkable technique that addresses this complexity by documenting the expression of thousands of genes at the level of mRNA abundance. From the standpoint of clinical investigation, the initial focus of gene profiling experiments has been on screening primary tumors for markers of poor prognosis. However this is only a first step in demonstrating the utility of this technique. Future advances will focus on understanding the evolution of an organ confined primary cancer to a treatment resistant lethal systemic disease through repeated tumor sampling and analysis, an approach termed in this paper "dynamic profiling". Using breast cancer endocrine therapy as an example our initial approaches to dynamic profiling will be described.

Aromatase Inhibitors↗

PubMed2002

Letrozole in the treatment of breast cancer.

Over the last 30 years the role of tamoxifen in breast cancer treatment has been progressively expanded by clinical investigation to encompass the entire spectrum of disease from cancer chemoprevention to palliation of advanced disease. The primacy of tamoxifen for these indications in postmenopausal women is now under challenge by the selective aromatase inhibitors, a class of endocrine agent that induces oestrogen deprivation rather than oestrogen receptor blockade. This review considers the biochemical, pharmacological and clinical properties of the nonsteroidal aromatase inhibitor letrozole. This agent is superior to tamoxifen for the treatment of metastatic breast cancer, a finding that suggests that letrozole may ultimately eclipse tamoxifen for other indications, including chemoprevention. Further clinical investigation will be necessary to establish the risks and benefits of letrozole versus tamoxifen for each new indication, with adjuvant therapy being the next in line. The object of this review is to provide a reference source on the biochemical, pharmacological and clinical properties of letrozole for clinicians to consider both established and future indications.

Antineoplastic Agents↗

PubMedDate not supplied

Dramatic response of choroidal metastases from breast cancer to a combination of trastuzumab and vinorelbine.

We report the case of a 57-year-old woman with unilateral choroidal metastases from HER-2-positive breast cancer. She was given trastuzumab and vinorelbine with complete resolution of her visual defect after one cycle of treatment. This article illustrates that treatment using trastuzumab-containing chemotherapy regimens in HER-2-overexpressing breast cancer patients with choroidal metastases may be an alternative therapeutic strategy to initial orbital irradiation.

Angiography↗