Retrospective analysis of HER2 expression status as a prognostic factor in PTK6-positive triple-negative breast cancer

The treatment of TNBC is usually challenging. This study explored the prognostic significance of PTK6 expression and its association with HER2-low expression in TNBC. We retrospectively enrolled 94 PTK6-positive TNBC patients from various disease stages. All patients were categorized into HER2-low (including IHC 2+/FISH- and 1+) and HER2-zero (ultra-low and null) groups based on IHC and FISH results. Kaplan-Meier analysis and Cox proportional hazards models were used to assess disease-free survival (DFS) and overall survival (OS), with multivariate analysis identifying independent prognostic factors. We retrospectively enrolled 94 PTK6-positive TNBC patients with a median age of 51 years and a mean age of 51.17 years, from various disease stages. Among the 94 patients, 65% (61/94) were classified as HER2-low. HER2-low status was significantly associated with older age ( P = 0.019). No statistically significant differences were observed in DFS (HR = 0.89, 95% CI: 0.47–1.69, P = 0.66) or OS (HR = 1.14, 95% CI: 0.58–2.24, P = 0.69) between HER2-low and HER2-zero groups. Age and N stages were identified as independent prognostic factors for DFS ( P = 0.02 for age; P = 0.04 for stage N) and OS ( P = 0.03 for age; P = 0.07 for stage N). This study demonstrates that PTK6 expression in TNBC is associated with HER2-low expression, particularly in older patients. Although HER2-low status did not significantly impact overall survival in our cohort, age and nodal stage remain critical prognostic indicators. These findings highlight the heterogeneity within PTK6-positive TNBC and suggest the need for further research to clarify the clinical relevance of HER2-low expression in combination with PTK6 status.