The Spanish SOLTI-1716 TATEN trial evaluates the combination of pembrolizumab and paclitaxel in patients with hormone receptor-positive, HER2-negative metastatic breast cancer whose tumours, assessed with PAM50, fall into the HER2-enriched or basal-like subtypes after progression on a CDK4/6 inhibitor. The results suggest that chemo-immunotherapy may be effective in these genomically defined subtypes.
What was known
Hormone receptor-positive, HER2-negative metastatic breast cancer is biologically distinct from early-stage disease: it has a higher prevalence of genomically defined non-luminal subtypes, particularly HER2-enriched and basal-like. These tumours are highly proliferative, less dependent on hormone signalling and associated with poorer outcomes and early resistance to endocrine therapy and CDK4/6 inhibition, which calls for biomarker-driven strategies.
What this work adds
The SOLTI-1716 TATEN trial (NCT04251169) is a phase II, single-arm study evaluating the combination of pembrolizumab and paclitaxel in patients with hormone receptor-positive, HER2-negative metastatic breast cancer classified as HER2-enriched or basal-like by PAM50 after progression on a CDK4/6 inhibitor. 126 patients were screened with the PAM50 genomic assay and 20 with HER2-enriched or basal-like subtypes were enrolled, receiving pembrolizumab (200 mg every three weeks) and paclitaxel (80 mg/m2 weekly).
Main results
The overall response rate, the primary endpoint, was 61.1% (95% CI 35.7-82.7) and the clinical benefit rate was 94.4% (95% CI 72.7-99.9). Median progression-free survival was 8.1 months (95% CI 5.9-10.4) and median overall survival was 26 months (95% CI 18-not reached). Three patients achieved durable responses lasting 24 months or more. Gene expression analyses showed that high expression of proliferation- and immune-related genes predicted better responses and survival, whereas luminal-related gene expression was associated with lower clinical benefit.
What it means
The authors conclude that chemo-immunotherapy may be an effective strategy in the genomically defined non-luminal subtypes of hormone receptor-positive, HER2-negative metastatic breast cancer after CDK4/6 inhibitor resistance, and highlight the value of molecular subtyping to guide post-endocrine treatment decisions. This is a phase II study with a small number of patients, so the results must be confirmed.
Spanish context
The trial belongs to the SOLTI platform, a Spanish cooperative breast cancer research group that drives academic trials with genomic signatures. It reflects the commitment of Spanish groups to translational biology studies in populations selected by biomarkers, a line of work that enriches the care offered by breast units.
Reference: Conte B, Brasó-Maristany F, Pascual T, Hernando C, Vázquez S, Blanch S, et al. Pembrolizumab and Paclitaxel in Patients with HR+/HER2- Breast Cancer with HER2-Enriched or Basal-like Subtypes. Clinical Cancer Research, 2026. https://doi.org/10.1158/1078-0432.ccr-25-2570
