5-year outcomes of chemotherapy de-escalation in HER2-positive early breast cancer and exploratory circulating tumor DNA analyses from the randomized phase 2 PHERGain trial.

In PHERGain’s HER2-positive stages I–IIIA early breast cancer cohort, 5-year invasive disease-free survival was 89.5% in the de-escalation group and 92.4% among 18 F-FDG-PET responders achieving pCR without chemotherapy.

• Why it matters: Chemotherapy omission strategies need long-term safety and efficacy evidence, and biomarkers that can identify who can safely avoid chemotherapy are still lacking.
• What they did: PHERGain randomized operable HER2-positive breast cancer patients to receive HP with chemotherapy (group A) or HP with 18 F-FDG-PET response and pCR–adapted chemotherapy omission (group B), then assessed prespecified 5-year iDFS and exploratory ctDNA dynamics.
• The result: After median 5.6 years, detectable ctDNA at baseline or during treatment was linked to worse iDFS, while ctDNA clearance correlated with higher pCR rates and improved long-term outcomes, supporting PET-guided pCR adaptation and suggesting ctDNA for individualization.

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