Letrozole in the treatment of breast cancer

ESR1 Gene Mutations and Liquid Biopsy in ER-Positive Breast Cancers: A Small Step Forward, a Giant Leap for Personalization of Endocrine Therapy?

The predominant forms of breast cancer (BC) are hormone receptor-positive (HR+) tumors characterized by the expression of estrogen receptors (ERs) and/or progesterone receptors (PRs). Patients with HR+ tumors can benefit from endocrine therapy (ET). Three types of ET are approved for the treatment of HR+ BCs and include selective ER modulators, aromatase inhibitors, and selective ER downregulators. ET is the mainstay of adjuvant treatment in the early setting and the backbone of the first-line treatment in an advanced setting; however, the emergence of acquired resistance can lead to cancer recurrence or progression. The mechanisms of ET resistance are often related to the occurrence of mutations in the ESR1 gene, which encodes the ER-alpha protein. As ESR1 mutations are hardly detectable at diagnosis but are present in 30% to 40% of advanced BC (ABC) after treatment, the timeline of testing is crucial. To manage this resistance, ESR1 testing has recently been recommended; in ER+ HER2- ABC and circulating cell-free DNA, so-called liquid biopsy appears to be the most convenient way to detect the emergence of ESR1 mutations. Technically, several options exist, including Next Generation Sequencing and ultra-sensitive PCR-based techniques. In this context, personalization of ET through the surveillance of ESR1 mutations in the plasma of HR+ BC patients throughout the disease course represents an innovative way to improve the standard of care.

In Silico Mixed Ligand/Structure-Based Design of New CDK-1/PARP-1 Dual Inhibitors as Anti-Breast Cancer Agents

CDK-1 and PARP-1 play crucial roles in breast cancer progression. Compounds acting as CDK-1 and/or PARP-1 inhibitors can induct cell death in breast cancer with a selective synthetic lethality mechanism. A mixed treatment by means of CDK-1 and PARP-1 inhibitors resulted in radical breast cancer cell growth reduction. Inhibitors with a dual target mechanism of action could arrest cancer progression by simultaneously blocking the DNA repair mechanism and cell cycle, resulting in advantageous monotherapy. To this aim, in the present work, we identified compound 645656 with a significant affinity for both CDK-1 and PARP-1 by a mixed ligand- and structure-based virtual screening protocol. The Biotarget Predictor Tool was used at first in a Multitarget mode to filter the large National Cancer Institute (NCI) database. Then, hierarchical docking studies were performed to further screen the compounds and evaluate the ligands binding mode, whose putative dual-target mechanism of action was investigated through the correlation between the antiproliferative activity data and the target proteins' (CDK-1 and PARP-1) expression pattern. Finally, a Molecular Dynamics Simulation confirmed the high stability of the most effective selected compound 645656 in complex with both PARP-1 and CDK-1.

Complete response to pyrotinib combined with letrozole as first-line treatment of HER2-positive/HR-positive breast cancer: a case report

Approximately 15–20% of breast cancer patients are epidermal growth factor receptor 2 (HER2)-positive, and about half of these are also hormone receptor (HR)-positive. The mainstay treatment for HER2-positive/HR-positive patients is anti-HER2 treatment combined with chemotherapy. However, many patients are not suitable for this treatment regimen due to their poor physical health and inability to tolerate chemotherapy. Pyrotinib is a novel, irreversible tyrosine kinase inhibitor (TKI) with activity against EGFR/HER1, HER2, and HER4. Several studies have shown pyrotinib’s anti-tumor activity and safety profile in treating HER-2 positive breast cancer patients, but its effect on metastatic breast cancer (MBC) when combined with letrozole as a first-line treatment remains to be verified. Here, we present a case of a 50-year-old postmenopausal HER2-positive/HR-positive breast cancer patient who received pyrotinib plus letrozole as a first-line treatment following a diagnosis of left axillary lymph node and double lung metastases after modified radical mastectomy for left breast cancer. Two months after administration of combined pyrotinib and letrozole, a complete response (CR) was confirmed by CT scan. The patient experienced only mild and tolerable adverse events. At the time of writing, the patient was still alive without any recurrence. Our case indicates that the combined therapy of pyrotinib plus letrozole may/can be a promising treatment option for patients with HER2-positive/HR-positive MBC. Nevertheless, further evidence is needed to verify this conclusion.

FACE: the barefaced facts of AI potency

The use of third-generation aromatase inhibitors (AIs), such as anastrozole and letrozole, as initial adjuvant hormonal therapy in postmenopausal women (PMW) with hormone receptor-positive (HR+) breast cancer offers a significant benefit over tamoxifen for reducing recurrence risk. Clinical studies, including the Arimidex Tamoxifen Alone or in Combination (ATAC) and the Breast International Group (BIG) 1–98 trials, have proven that both anastrozole and letrozole are, respectively, superior to tamoxifen in improving disease-free survival. Although differing in design, objectives, and follow-up time, these trials offer some insight into the comparative clinical efficacy of these two nonsteroidal AIs. In particular, results from BIG 1–98 show that letrozole significantly reduces early distant metastatic (DM) events, which constitute the majority of early recurrence events. Subsequently, there is a beneficial overall survival effect emerging in the trial, whereas survival is unchanged with anastrozole after 100 months of follow-up in ATAC. Significant differences in the potency of these two drugs, vis-à-vis their degree of aromatase inhibition, have been observed in comparative trials and show that letrozole causes a more complete suppression of estrogen levels than does anastrozole. Whether this difference in potency is relevant to reductions in DM events during adjuvant therapy remains unclear. The Femara Anastrozole Clinical Evaluation trial is addressing this issue in a more unequivocal manner by comparing initial adjuvant treatment with anastrozole or letrozole in a population of breast cancer patients at high risk of recurrence: PMW with HR+ disease and axillary lymph node involvement.

Aromatase inhibitors for breast cancer: proven efficacy across the spectrum of disease

For more than 100 years, hormonal therapy has been known to be effective in the treatment of breast cancer. Initially, this therapy was dominated by the selective estrogen receptor antagonists such as tamoxifen. Aromatase inhibitors (AIs) are a distinct drug class with demonstrated activity in the treatment of hormone-sensitive breast cancer. All 3 third-generation AIs, exemestane, anastrozole, and letrozole, have been studied in multiple lines of therapy in advanced breast cancer and have demonstrated equivalence or superiority compared with tamoxifen. While initially developed as a treatment option for advanced disease, the AIs have also shown efficacy in the treatment of curable disease, including the neoadjuvant and adjuvant settings. In addition, the AIs demonstrate a tolerable side effect profile in comparison with tamoxifen, and this has led to their early incorporation as standard of care therapy. Given the proven efficacy of AIs across the spectrum of breast cancer, the remaining questions include definitive sequencing strategy, timing, and duration of use. Ongoing trials include head-to-head comparisons between the AIs in early-stage breast cancer; the results of these trials are eagerly anticipated and should further optimize the use of AIs.

The impact of adjuvant endocrine therapy on reducing the risk of distant metastases in hormone-responsive breast cancer

SUMMARY

The primary goal of systemic adjuvant therapy for breast cancer is to control the risk of recurrence following surgery, thereby improving long-term survival. For many years, tamoxifen has served as the standard adjuvant endocrine therapy for postmenopausal women with hormone-sensitive breast cancer. The entry of the third-generation aromatase inhibitors (AIs) exemestane, anastrozole and letrozole as adjuvant therapy has introduced several different treatment options. Indirect comparisons suggest that appreciable differences may exist between the AIs in terms of early risk reduction, especially the risk for early distant metastases. Possible differences in efficacy may be related to differences in potency. Two ongoing trials directly comparing two AIs - the Femara versus Anastrozole Clinical Evaluation and MA.27 - may provide further information.

Aromatase inhibitors in early breast cancer therapy: a variety of treatment strategies

Until recently, standard endocrine therapy for estrogen receptor-positive early breast cancer in the preoperative neoadjuvant and postoperative adjuvant settings was the selective estrogen receptor modulator tamoxifen. An alternate therapeutic approach is to suppress total-body estrogen synthesis using an aromatase inhibitor. The highly potent and specific third-generation aromatase inhibitors (anastrozole, exemestane and letrozole) have consistently demonstrated improved efficacy over tamoxifen in large randomised neoadjuvant and adjuvant clinical trials. As neoadjuvant therapy, compared with tamoxifen, all three aromatase inhibitors significantly improved breast-conserving surgery rates, but only letrozole achieved a significantly higher overall response rate. These agents have also been evaluated in three adjuvant strategies: instead of tamoxifen for 5 years, sequenced after 2-3 years of tamoxifen, or as extended adjuvant therapy following a full 5-year course of tamoxifen. In all cases, the aromatase inhibitor was significantly more effective in reducing the risk of recurrence, compared with tamoxifen in the first two approaches and with placebo or no treatment as extended therapy. Long-term aromatase inhibitor treatment is associated with less endometrial cancer, thromboembolic events and strokes than tamoxifen, but more musculoskeletal disorders and bone loss. Further investigation is focusing on identification of the patient subgroups most likely to benefit from each of these adjuvant therapy options.