Genomic landscape of triple-negative breast cancer in South Asian populations: a systematic review.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by the absence of estrogen receptor, progesterone receptor, and HER2 expression, and is associated with limited targeted treatment options and poor clinical outcomes. Although major genomic studies have characterized TNBC in Western populations, the genomic landscape of TNBC in South Asian populations remains insufficiently understood despite a relatively high disease burden in this region. We conducted a systematic review following PRISMA 2020 guidance to synthesize available genomic evidence on TNBC in South Asian cohorts. Studies reporting genomic alterations in TNBC patients from South Asia were identified through searches of PubMed, Scopus, Web of Science, and ProQuest, supplemented by citation tracking and a ClinicalTrials.gov search. Eight studies from India and Pakistan met the eligibility criteria. Because the evidence base was sparse and clinically and methodologically heterogeneous, and because the number of studies reporting extractable denominators for any single biomarker did not reach our pre-specified threshold for pooling, data were synthesized descriptively rather than by meta-analysis. Across the included studies, recurrent alterations were reported in key tumor-suppressor and DNA-repair genes, particularly BRCA1, BRCA2, and TP53. Germline BRCA1 alterations were reported at a relatively high frequency in several cohorts, most notably in Pakistani TNBC patients, suggesting a contribution of hereditary DNA-repair defects to TNBC pathogenesis in this population. These findings highlight the importance of population-specific genomic analyses and support the growing role of DNA-repair-directed therapies and biomarker-driven precision oncology strategies in TNBC management. We additionally propose, as recommendations for future work, a two-tier framework for ancestry classification and a tiered scheme for harmonizing homologous recombination deficiency (HRD) reporting.