The Spanish SOLTI-1303 PATRICIA trial (cohort C) compares the triplet of palbociclib, trastuzumab and endocrine therapy against the physician’s choice of standard treatment in previously treated patients with HER2-positive, hormone receptor-positive advanced breast cancer of PAM50 luminal A or B subtype. The combination significantly improved progression-free survival.
What was known
Based on the results of cohorts A and B of the SOLTI-PATRICIA trial, a direct comparison with standard-of-care treatments was needed to assess the efficacy and safety of palbociclib, trastuzumab and endocrine therapy in pretreated patients with PAM50 luminal A or B tumours.
What this work adds
SOLTI-PATRICIA cohort C is a randomised, multicentre, prospective, open-label phase II study. Pretreated patients with HER2-positive, hormone receptor-positive, PAM50 luminal A or B advanced breast cancer were randomised 1:1 to receive the triplet or trastuzumab-based treatment of the physician’s choice. Patients in the physician’s choice arm could be re-randomised upon progression if they still met the criteria. The primary endpoint was investigator-assessed progression-free survival per RECIST version 1.1.
Main results
A total of 264 participants were prescreened between August 2019 and 2023, and 73 patients were randomised (including seven re-randomisations). In the physician’s choice arm, 48.5% received trastuzumab plus chemotherapy, 39.4% trastuzumab emtansine and 12.1% trastuzumab plus endocrine therapy. The triplet was associated with significantly better progression-free survival than standard treatment (stratified hazard ratio 0.52; 95% CI 0.29-0.95; two-sided p = 0.03). Progression-free survival rates at 24 months were 24.0% with the triplet and 4.3% with the physician’s choice. The overall response rate was 18.9% (95% CI 8.6-35.7) versus 7.1% (95% CI 1.2-25.0). In the triplet arm, grade 3 or higher adverse events occurred in 61.5% of patients, neutropenia being the most frequent (53.9%), with no permanent discontinuations due to toxicity.
What it means
The authors conclude that combining palbociclib, trastuzumab and endocrine therapy was safe and significantly improved progression-free survival versus the physician’s choice in previously treated patients with HER2-positive, PAM50 luminal A or B advanced breast cancer. The benefit must be weighed against the haematological toxicity, notable but manageable, and against the limited sample size inherent to a phase II trial.
Spanish context
The trial is part of the SOLTI platform, a leading Spanish cooperative group in academic breast cancer research, and shows the ability of Spanish centres to lead randomised trials with molecular patient selection. This kind of research strengthens the position of Spanish breast units in the development of targeted therapies.
Reference: Ciruelos E, Pascual T, Villacampa G, Pernas S, Sanchez-Bayona R, Ponce J, et al. Palbociclib, Trastuzumab, and Endocrine Therapy in Pretreated HER2-Positive and PAM50 Luminal Advanced Breast Cancer: Randomized Phase II, SOLTI-1303 PATRICIA Trial. Clinical Cancer Research, 2026. https://doi.org/10.1158/1078-0432.ccr-25-2882
