Influences of adjuvant treatments in hormone receptor positive breast cancer on receptor conversion in recurrent breast cancer

Significance and possible causes of hormone receptor expression loss in metastatic breast cancer. Phenotypic evolution of luminal <i>BRCA1</i>-associated breast cancer to triple negative subtype in lung metastasis and PARP inhibition strategy in early-line therapy

Current clinical recommendations indicate the need for a biopsy of a metastatic focus in metastatic breast cancer (BC), but the optimal frequency of additional molecular analysis remains unclear. The discordance of hormonal receptors (HR) between the primary tumor and metastatic foci has prognostic significance, while the transition from HR-positive BC to a triple negative phenotype is associated with a worse clinical prognosis. Acquisition of HR expression in primary triple negative BC is more favorable due to the wide range of options for HR-positive BC treatment. Over the past few years, PARP inhibitors have become an important therapeutic option for the treatment of various tumor types, including BC and luminal surrogate subtypes. However, some questions still remain unresolved, the most important of which are: what is the optimal sequence of the use of CDK4 / 6 inhibitors as part of combined hormone therapy and PARP inhibitors in luminal types of BRCA-associated BC and how effective is the strategy of PARP inhibition after the use of combined hormone therapy with CDK4 / 6 inhibitors? It is obvious that the answers to the questions can be partially obtained by performing a biopsy of the most clinically significant metastatic focus and selecting therapy according to the phenotypic surrogate subtype. A clinical case of the phenotypic evolution of HR-positive BRCA1-associated BC into a triple negative phenotype during metastasis to the lungs and the luminal phenotype of tumor metastasis in soft tissues is presented. Biopsy of the most clinically significant metastatic lesion in the lungs in this case changed the strategy of early-line therapy for estrogen-receptor-positive disease, when in the absence of a biopsy, a combined hormone therapy regimen with CDK4 / 6 inhibitors could be applied. At the same time, the strategy of using PARP inhibitor talazoparib, which has shown efficacy in all surrogate subtypes, should certainly be prescribed in the early line of therapy for BRCA-associated disease with loss of estrogen receptor expression. Despite the luminal phenotype of metastasis in the soft tissues of the back and the unknown status of bone metastases, the drug demonstrates efficacy in these cases as well. It should be noted that partial response according on RECIST 1.1 months with an improvement in the quality of life and the disappearance of pain syndrome was evaluated after 10 weeks of treatment. The response duration was an unprecedented 10 months.

Prognostic significance of receptor expression discordance between primary and recurrent breast cancers: a meta-analysis

PURPOSE

This meta-analysis aimed to investigate whether receptor (estrogen receptor [ER], progesterone receptor [PR], and human epidermal growth factor receptor 2 [HER2]) discordances between primary and recurrent breast cancers affect patients' survival.

METHODS

Search terms contained ER, PR, and HER2 status details in both primary and recurrent tumors (local recurrence or distant metastasis) in addition to survival outcome data (overall survival [OS] or post-recurrence survival [PRS]).

RESULTS

Loss of ER or PR in recurrent tumors was significantly associated with shorter OS as compared with receptor-positive concordance (hazard ratio [HR], 1.67; 95% confidence interval [% CI] 1.37-2.04; p < 0.00001 and HR, 1.45; 95% CI 1.21-1.75; p < 0.0001, respectively). Similar trends were observed in groups with only distant metastasis. Gain of ER was a significant predictor of longer PRS as compared with receptor-negative concordance (HR, 0.76; 95% CI 0.59-0.97; p = 0.03). Gain of PR was not a significant predictor of longer survival compared with receptor-negative concordance, but it could be related to better OS at distant metastasis. Both HER2 of loss and gain could be related to poor outcomes.

CONCLUSION

This meta-analysis showed that receptor conversion in recurrent tumors may affect patient survival as compared with receptor concordance.

The rate of estrogen receptor-conversion associated with tumor progression in estrogen receptor-positive breast cancer patients following adjuvant Tamoxifen administration

Background

Hormone Receptor (HR)‐discordance between primary breast cancer and metastasis is a known biological phenomenon. Discordance studies usually comprise a heterogeneous group of HR‐positive and negative patients and allow for the comparison of changes in HR‐status from the primary to the recurrent disease. However, in a clinical setting, the rate of estrogen receptor‐conversion following endocrine therapy with agents such as Tamoxifen (TAM) in estrogen receptor‐positive cancers is of primary interest as opposed to total receptor discordance.

Aim

To investigate the rate of estrogen receptor‐conversion associated with tumor progression in estrogen receptor‐positive breast cancer patients following adjuvant TAM administration and to compare the results with the meta‐analysis data of HR‐discordance studies.

Methods and Results

A retrospective double‐center review of biomarkers in 67 estrogen receptor‐positive breast cancer patients who underwent TAM treatment in the adjuvant setting. The estrogen and progesterone receptor‐status were compared at the time of diagnosis and following relapse and the Disease‐free Survival, mean duration of TAM treatment as well as the operative, radiation, and cytotoxic therapies registered before TAM treatment, were recorded.

Initially, all patients were estrogen receptor‐positive. The average age at the time of diagnosis was 52.8 ± 12.4 years. After recurrence, only 47 patients (70.1%) were still estrogen receptor‐positive with a highly significant loss of estrogen receptor‐expression in 29.9% of cases. The mean duration of TAM treatment was 40.7 ± 19.9 months. 45 patients (i.e., 67.2%) progressed during the TAM treatment and the remaining 22 patients (32.8%) developed relapse after the TAM treatment had finished. Initially, there were 82.1% progesterone receptor‐positive and 17.9% progesterone receptor‐negative, but after relapse the progesterone receptor‐positive cases diminished significantly to 53.7%, showing a progesterone receptor‐loss of 28.4%.

Conclusion

The rate of estrogen receptor‐loss associated with tumor progression following TAM treatment is approximately 30%, which is of clinical relevance in order to evaluate further endocrine efficacy in these patients. This rate of receptor conversion is roughly 6‐13% higher compared to the recently published meta‐analysis data of discordance studies. This discrepancy could possibly be due to anti‐hormonal therapy with TAM accentuating receptor conversion.

Hormone Receptor Loss in Breast Cancer: Molecular Mechanisms, Clinical Settings, and Therapeutic Implications

Hormone receptor-positive breast cancer (HR+ BC) accounts for approximately 75% of new BC diagnoses. Despite the undisputable progresses obtained in the treatment of HR+ BC in recent years, primary or acquired resistance to endocrine therapies still represents a clinically relevant issue, and is largely responsible for disease recurrence after curative surgery, as well as for disease progression in the metastatic setting. Among the mechanisms causing primary or acquired resistance to endocrine therapies is the loss of estrogen/progesterone receptor expression, which could make BC cells independent of estrogen stimulation and, consequently, resistant to estrogen deprivation or the pharmacological inhibition of estrogen receptors. This review aims at discussing the molecular mechanisms and the clinical implications of HR loss as a result of the therapies used in the neoadjuvant setting or for the treatment of advanced disease in HR+ BC patients.