CDK4/6 Inhibitor Combination Therapy in HER2+ Disease

The PATINA trial findings established the efficacy of adding CDK4/6 inhibitors to hormone receptor–positive, HER2-positive breast cancer treatment following induction chemotherapy. Building on preclinical work demonstrating CDK4/6 inhibitor activity in both ER-positive and HER2-positive cell lines, the trial randomly assigned patients with triple-positive disease after completing taxane-based induction with dual anti-HER2 blockade to maintenance therapy with either endocrine therapy plus HER2 blockade or endocrine therapy plus palbociclib with dual anti-HER2 blockade.

The addition of palbociclib demonstrated statistically significant improvement in median progression-free survival to 44 months, representing unprecedented treatment durability in this patient population. This approach provides an attractive treatment option for the 50% to 60% of patients with HER2-positive disease that is also ER positive, offering enhanced disease control through the addition of CDK4/6 inhibition to standard maintenance therapy.

Clinical implementation faces access challenges requiring prior authorization and peer-to-peer reviews to justify the combination approach. Success rates vary among institutions and insurance providers, with some oncologists reporting difficulty obtaining approval despite compelling efficacy data. The anticipated publication of full trial results may strengthen the evidence base for broader adoption. The combination represents a significant advancement for patients with triple-positive breast cancer, though practical access issues currently limit widespread implementation in clinical practice.