Clinical TP53 genetic testing is recommended for HER2-positive breast cancer patients aged 35 or younger

Limited information is available for TP53 pathogenic variants (PVs) in early-onset breast cancer patients in China. We investigated the prevalence and clinical relevance of TP53 PVs among 1492 BRCA1/2-negative early-onset breast cancer patients. Peripheral blood samples were collected for TP53 genetic testing through next-generation sequencing. Finally, TP53 PVs were identified in 7 patients (0.47%). The variants p.R248P, p.I251F, and p.G266R were identified for the first time in germline mutations. TP53 carriers exhibited significantly younger diagnosis age (p = 0.003) and higher prevalence of HER2-positive disease (p = 0.020). All carriers were diagnosed before age 35. In HER2-positive patients ≤35 years, the prevalence of TP53 PVs was 2.3%, significantly higher than others after adjusting for a family history of breast cancer and/or ovarian cancer and a personal history of bilateral breast cancer (OR = 13.57, p = 0.002). These results support TP53 genetic testing prioritization for HER2-positive patients under 35 years to guide clinical management, while validation in diverse populations remains essential.