Clinical trials update: endocrine and biological therapy combinations in the treatment of breast cancer

A greater understanding of the biological mechanisms responsible for de novo and acquired endocrine resistance has led to the rational design of clinical trials exploring the benefit of combining hormonal therapies with novel biological agents in an effort to enhance the efficacy of ER+ breast cancer treatment. These studies are increasingly including parallel biological analyses to elucidate the molecular characteristics of those tumors that are most likely to respond to specific targeted/endocrine combinations in an effort to develop a tailored approach to the management of individual patients. Unfortunately despite encouraging preclinical data, some of these combinations have yielded disappointing results in the clinical setting. This article will review the results of clinical trials of endocrine/biological combinations conducted in early and advanced breast cancer as well as provide an update on ongoing studies.

Novel therapeutic strategies combining antihormonal and biological targeted therapies in breast cancer: focus on clinical trials and perspectives

Several models have been proposed to explain the mechanisms of endocrine resistance including aberrant growth-signaling pathways, and have led to the rational design of studies combining hormonotherapy with signal transduction inhibitors (STI) in advanced breast cancer. This article reviews the current status of these clinical trials. Preliminary results from the randomized controlled trials are rather disappointing. The mTOR inhibitor temsirolimus and the farnesyl transferase inhibitor tipifarnib combined with letrozole did not show any benefit compared to letrozole alone. As neoadjuvant therapy, gefinitib did not enhance the response rate induced by anastrozole. Interesting results were obtained with exemestane combined to celecoxib but should be further explored with adequate cardiac monitoring. Trastuzumab combined with anastrozole was more effective than anastrozole in terms of response rate and progression-free survival but not survival. Several controlled trials as first- or second-line therapy have started recently and over the next few years we should learn whether this approach will provide significant gains in efficacy.

Predictors of response to aromatase inhibitors

Aromatase inhibitors are now considered to be part of the endocrine treatment for most hormone receptor-positive breast cancer in post-menopausal women for both early and advanced disease. Despite the impressive efficacy of these agents, up to 50% of treated patients exhibit de novo or intrinsic resistance to aromatase inhibitors and hence identification of response predictors is essential to allow treatment to be directed towards responsive populations and for alternative or additional therapies to be offered to resistant patients. Emerging data seem to suggest a role for the conventional tumour markers of oestrogen receptor and progesterone receptor as possible predictors of response but, particularly in the adjuvant setting, the extent to which these are useful has not been fully elucidated. Data from both the neo-adjuvant and advanced disease settings suggest that response to aromatase inhibitors does not appear to be adversely affected by HER-2 overexpression. Within neo-adjuvant aromatase inhibitor studies, the proliferation marker Ki67 has shown a significant correlation with relapse-free survival, suggesting a role in prediction for measurement of Ki67 and other dynamic markers of response. Analysis of multiple gene expression changes over a short treatment period may also have potential clinical utility for prediction of response.

Emerging targeted therapies for breast cancer

Breast cancer is the most common neoplasia among women in the world. For the last few years there has been an increasing interest in the development of agents against molecular targets considered to be involved in the process of malignant transformation or tumor progression. Experimental data indicate that various intracellular signaling pathways may be activated or overexpressed in patients who have breast cancer. Targeted therapies against these pathways have recently become one of the most active and promising areas of development in oncology.

Adjuvant endocrine therapy for early breast cancer

Breast cancer is the most common cancer among women and about 80% of breast cancers express hormone receptors. Tamoxifen has been the most important form of adjuvant endocrine therapy over the last 25 years. The third generation aromatase inhibitors (AIs) are a new class of drugs challenging the central role of tamoxifen as adjuvant endocrine treatment in postmenopausal women with hormone receptor-positive breast cancer. Their effectiveness has been demonstrated in first line therapy as well in neoadjuvant setting with a statistically significant superiority over tamoxifen. Here we considered the role of adjuvant AIs in early stage breast cancer with an analysis reviewing the main adjuvant trials. We considered efficacy, side effects, optimal timing, duration of the therapy and whether specific subgroups may achieve particular benefit. In conclusion the upfront use of adjuvant anastrozole or letrozole is superior to tamoxifen with a good relative toxicity profile. Tamoxifen will continue to have a role where recurrence risk is low or if AI is poorly tolerated. Issues including the timing of administration (up-front or sequential), the duration of the therapy and the role of biomarkers such as PgR and HER2 in optimal selection remain unresolved.

Primary systemic therapy for operable breast cancer: A review of clinical trials and perspectives

Primary systemic therapy represents the standard of care for locally advanced breast cancer and has becoming an attractive alternative in earlier stages. A part from the proven advantage of increasing the rate of breast conservative surgery, the up front use of systemic therapy can allow for an in vivo test of treatment sensitivity, and response to primary treatment discriminates patients at different prognosis. This review will summarize the more relevant data on the preoperative treatment with chemotherapy, hormonal therapy and targeted agents.

Place actuelle des inhibiteurs de l'aromatase dans le traitement adjuvant des cancers du sein

Adjuvant hormone therapy is indicated only in patients whose tumors express estrogen or progesterone receptors. Aromatase inhibitors (AI) are indicated only in postmenopausal patients. AI are significantly more effective than tamoxifen in terms of disease-free survival and distant recurrence-free survival; these advantages will probably result in a significant overall survival benefit after sufficient follow-up. This benefit justifies the use of AI in all postmenopausal patients in the absence of contraindications and after complete explanations of the benefit/risk ratio and potential side effects of this treatment. The benefit of AI over tamoxifen may be particularly pronounced for tumors overexpressing HER-2 and perhaps for ER+PR- tumors. Replacement of tamoxifen by AI or first-line treatment with AI is advised in patients with such tumors. Extended adjuvant treatment with AI for 5 years significantly increases survival among patients already treated with tamoxifen for 5 years; it also provides a significant overall survival benefit to patients with positive axillary nodes and should be used in this group. AI may cause several generally mild side effects, including insomnia, arthralgia, bone loss, vaginal dryness, dyspareunia and loss of libido. Tamoxifen may be appropriate for well-informed patients with these side effects, especially those with RE+ RP+ tumors and a low risk of thromboembolic or endometrial complications. The effects of AI on memory and cognition should also be investigated thoroughly before its long-term use, especially in the elderly.

Estrogen Receptor Pathway: Resistance to Endocrine Therapy and New Therapeutic Approaches

Endocrine therapy is widely accepted as the most important treatment for all patients with hormone receptor-positive breast cancer. However, despite the positive effect of endocrine therapy on clinical outcome, resistance to these drugs inevitably develops. This article reviews the problem of resistance to hormonal therapy and addresses potential approaches to overcome intrinsic or acquired mechanisms of resistance.