Predominance of BRCA2 Mutation and Estrogen Receptor Positivity in Unselected Breast Cancer with BRCA1 or BRCA2 Mutation

Efficacy of adjuvant CDK4/6 inhibitors in hormone receptor-positive breast cancer: a systematic review and meta-analysis

BACKGROUND

The combination of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and standard endocrine therapy (ET) in the adjuvant treatment of hormone receptor (HR)-positive/HER2-negative breast cancer (BC) has yielded conflicting results. We performed a pooled analysis of the adjuvant efficacy of CDK4/6 inhibitors by including data from the NATALEE trial, the most recent trial on this topic.

METHODS

We searched major databases and congress proceedings until 7 June 2023 to identify randomized controlled trials (RCT) comparing adjuvant CDK4/6 inhibitor plus ET combination versus ET in HR-positive/HER2-negative early-stage BC.

RESULTS

Four RCTs involving a total of 17,749 patients were included. According to the pooled analysis of these four studies, significant improvement in invasive disease-free survival (iDFS) was observed with the addition of CDK4/6 inhibitors to standard ET (HzR: 0.81, 95% CI 0.67-0.97). IDFS benefit was irrespective from menopausal status, Ki-67 index, tumor grade, and previous chemotherapy. CDK4/6 inhibitors plus ET had a significant improvement in iDFS in stage 3 whereas there was a trend toward better iDFS in stage 2 (HzR for stage 3: 0.67, 95% CI 0.58-0.78; HzR for stage 2: 0.74, 95% CI 0.55-1.01).

CONCLUSIONS

Addition of CDK4/6 inhibitors to standard ET in the adjuvant treatment of HR-positive/HER2-negative early-stage BC improves iDFS.

Metaplastic breast cancer: an all-round multidisciplinary consensus

Metaplastic breast cancer (MpBC) is a rare and aggressive histologic subtype of breast cancer (BC) characterized by the presence of at least two cellular types, commonly epithelial and mesenchymal components. Despite growing evidence that MpBC is a unique entity, it has long been treated as a variant of nonspecial type (NST) BC. MpBC typically shows the phenotype of triple-negative breast cancer (TNBC), but compared to NST-TNBC, it is a relatively chemorefractory tumor associated with worse outcomes. Therefore, there is an urgent need to develop management guidelines specifically for MpBC to improve the prognosis of patients with early MpBC. This expert consensus aims to guide diagnosis and standardize clinical management of early MpBC among treating physicians. We provide guidance on the challenging radiological and pathological diagnosis of MpBC. Evidence on the involvement of genetic predisposition in the development of MpBC is also explored. We emphasize the importance of a multidisciplinary approach for the treatment of patients with early MpBC. The optimal surgery and radiotherapy approach is presented, as well as the opportunity offered by novel therapeutic approaches to increase treatment response in this chemoresistant subtype. Appropriate management of patients with MpBC is critical to reduce the high risk of local and distant recurrence that characterizes this disease.

BRCA1-methylated triple negative breast cancers previously exposed to neoadjuvant chemotherapy form RAD51 foci and respond poorly to olaparib

Background

About 15% of Triple-Negative-Breast-Cancer (TNBC) present silencing of the BRCA1 promoter methylation and are assumed to be Homologous Recombination Deficient (HRD). BRCA1-methylated (BRCA1-Me) TNBC could, thus, be eligible to treatment based on PARP-inhibitors or Platinum salts. However, their actual HRD status is discussed, as these tumors are suspected to develop resistance after chemotherapy exposure.

Methods

We interrogated the sensitivity to olaparib vs. carboplatin of 8 TNBC Patient-Derived Xenografts (PDX) models. Four PDX corresponded to BRCA1-Me, of which 3 were previously exposed to NeoAdjuvant-Chemotherapy (NACT). The remaining PDX models corresponded to two BRCA1-mutated (BRCA1-Mut) and two BRCA1-wild type PDX that were respectively included as positive and negative controls. The HRD status of our PDX models was assessed using both genomic signatures and the functional BRCA1 and RAD51 nuclear foci formation assay. To assess HR restoration associated with olaparib resistance, we studied pairs of BRCA1 deficient cell lines and their resistant subclones.

Results

The 3 BRCA1-Me PDX that had been exposed to NACT responded poorly to olaparib, likewise BRCA1-WT PDX. Contrastingly, 3 treatment-naïve BRCA1-deficient PDX (1 BRCA1-Me and 2 BRCA1-mutated) responded to olaparib. Noticeably, the three olaparib-responsive PDX scored negative for BRCA1- and RAD51-foci, whereas all non-responsive PDX models, including the 3 NACT-exposed BRCA1-Me PDX, scored positive for RAD51-foci. This suggested HRD in olaparib responsive PDX, while non-responsive models were HR proficient. These results were consistent with observations in cell lines showing a significant increase of RAD51-foci in olaparib-resistant subclones compared with sensitive parental cells, suggesting HR restoration in these models.

Conclusion

Our results thus support the notion that the actual HRD status of BRCA1-Me TNBC, especially if previously exposed to chemotherapy, may be questioned and should be verified using the BRCA1- and RAD51-foci assay.