Efficacy of Fulvestrant in Women with Hormone-Resistant Metastatic Breast Cancer (mBC): A Canadian Province Experience

Oestrogen receptor positive breast cancer and its embedded mechanism: breast cancer resistance to conventional drugs and related therapies, a review

Traditional medication and alternative therapies have long been used to treat breast cancer. One of the main problems with current treatments is that there is an increase in drug resistance in the cancer cells owing to genetic differences such as mutational changes, epigenetic changes and miRNA (microRNA) alterations such as miR-1246, miR-298, miR-27b and miR-33a, along with epigenetic modifications, such as Histone3 acetylation and CCCTC-Binding Factor (CTCF) hypermethylation for drug resistance in breast cancer cell lines. Certain forms of conventional drug resistance have been linked to genetic changes in genes such as ABCB1, AKT, S100A8/A9, TAGLN2 and NPM. This review aims to explore the current approaches to counter breast cancer, the action mechanism, along with novel therapeutic methods endowing potential drug resistance. The investigation of novel therapeutic approaches sheds light on the phenomenon of drug resistance including genetic variations that impact distinct forms of oestrogen receptor (ER) cancer, genetic changes, epigenetics-reported resistance and their identification in patients. Long-term effective therapy for breast cancer includes selective oestrogen receptor modulators, selective oestrogen receptor degraders and genetic variations, such as mutations in nuclear genes, epigenetic modifications and miRNA alterations in target proteins. Novel research addressing combinational therapies including maytansine, photodynamic therapy, guajadiol, talazoparib, COX2 inhibitors and miRNA 1246 inhibitors have been developed to improve patient survival rates.

Retrospective Evaluation of Fulvestrant Efficacy and Clinical Results in Patients Using Fulvestrant

AIM

Fulvestrant is a drug used in the treatment of metastatic hormone receptor-positive breast cancer (mHRPBC). Although clinical trials have shown the efficacy of fulvestrant, real-life data are limited and data from clinical trials and real-life settings sometimes may be seen differently. Therefore, we retrospectively reviewed mHRPBC patients followed in our center and taking fulvestrant to evaluate the efficacy and clinical outcomes of the drug and also to identify factors affecting the efficacy and clinical outcomes of fulvestrant.

MATERIALS AND METHODS

Patients who were followed up with the diagnosis of metastatic breast cancer between 2010 and 2022 and using fulvestrant were retrospectively analyzed.

RESULTS

The median progression-free survival (PFS) time was 9 [95% confidence interval (CI): 7.13-10.18] months and the median overall survival time was 28 (95% CI: 22.53-34.93) months. According to multivariate analyses, PFS was associated with age (p=0.041), body mass index (BMI) (p=0.043), brain metastasis (p=0.033), fulvestrant line (p=0.002), and use of pre-fulvestrant chemotherapy (p=0.032).

CONCLUSION

Fulvestrant is an effective drug in mHRPBC. Fulvestrant is more effective in patients whose BMI index is under 30, without brain metastases, without prior chemotherapy, under 65 years of age, and used fulvestrant in the early treatment line. The efficacy of fulvestrant may vary according to age and BMI.

Towards Unravelling the Role of ERα-Targeting miRNAs in the Exosome-Mediated Transferring of the Hormone Resistance

Hormone therapy is one of the most effective breast cancer treatments, however, its application is limited by the progression of hormonal resistance, both primary or acquired. The development of hormonal resistance is caused either by an irreversible block of hormonal signalling (suppression of the activity or synthesis of hormone receptors), or by activation of oestrogen-independent signalling pathways. Recently the effect of exosome-mediated intercellular transfer of hormonal resistance was revealed, however, the molecular mechanism of this effect is still unknown. Here, the role of exosomal miRNAs (microRNAs) in the transferring of hormonal resistance in breast cancer cells has been studied. The methods used in the work include extraction, purification and RNAseq of miRNAs, transfection of miRNA mimetics, immunoblotting, reporter analysis and the MTT test. Using MCF7 breast cancer cells and MCF7/T tamoxifen-resistant sub-line, we have found that some miRNAs, suppressors of oestrogen receptor signalling, are overexpressed in the exosomes of the resistant breast cancer cells. The multiple (but not single) transfection of one of the identified miRNA, miR-181a-2, into oestrogen-dependent MCF7 cells induced the irreversible tamoxifen resistance associated with the continuous block of the oestrogen receptor signalling and the activation of PI3K/Akt pathway. We suppose that the miRNAs-ERα suppressors may act as trigger agents inducing the block of oestrogen receptor signalling and breast cancer cell transition to an aggressive oestrogen-independent state.