Objective:

To examine the extent, causes, and clinical implications of homologous recombination deficiency (HRD) in basal-like breast carcinoma (BLBC), emphasizing its significance in patient outcomes.

Key Findings:

• BLBC accounts for 15-20% of breast cancer cases and is associated with poor prognosis, highlighting the need for targeted therapies.
• BLBC shares histo-molecular characteristics with BRCA1-deficient tumors, suggesting potential HRD, which could inform treatment strategies.
• The clinical implications of HRD in BLBC remain incompletely defined, with most evidence derived from TNBC cohorts, indicating a need for subtype-specific studies.
• Functional studies indicate that only a subset of basal-like tumors exhibit true HRD despite genomic alterations, suggesting variability in treatment response.
• The predictive value of HRD in breast cancer is controversial compared to its established role in ovarian cancer, necessitating further investigation.

Interpretation:

While HRD may be enriched in BLBC, its clinical relevance and therapeutic implications require further investigation in molecularly defined cohorts, particularly focusing on treatment outcomes.

Limitations:

• Most studies on HRD derive from TNBC cohorts, which may obscure subtype-specific patterns; future studies should focus on BLBC.
• The biological complexity of HRD and temporal dynamics complicate the assessment of its clinical significance, suggesting a need for longitudinal studies.

Conclusion:

A BLBC-centered approach may provide a more biologically homogeneous context for studying HRD, but its clinical relevance is yet to be established, underscoring the importance of future research in this area.