PHERGain
Using an early PET scan to spot responders let a third of women be cured of HER2-positive breast cancer without any chemotherapy.
Overview
PET responders after 2 cycles continued antibodies alone; those achieving pCR (37.9% of the arm) skipped chemotherapy entirely. 3-year iDFS 95.4% in the PET-adapted arm, meeting its co-primary endpoint. Discussed at ESMO Breast 2026 as the model for imaging-guided de-escalation; a phase 3 (PHERGain-2) is underway.
Setting
HER2+ early breast cancer: chemotherapy-free trastuzumab + pertuzumab with early 18F-FDG PET response assessment to decide whether chemotherapy is needed
Phase
Phase 2
Sponsor
MEDSIR
Registry
Headline result
3-year iDFS 95.4% in the PET-adapted arm; ~1 in 3 spared chemotherapy.
Reported
2024
Enrolled
377 enrolled
Replication
Consistent with WSG-ADAPT HER2+/HR- (pCR-guided de-escalation); phase 3 confirmation pending.
In plain words
What these results mean for people, not percentages
3-year invasive disease-free survival (PET-adapted arm)primarysurrogate endpoint
- 95.4 out of 100 people alive without the cancer coming back at 3 years with PET-adapted HP ± chemotherapy.
- There was no comparison group, so this number cannot tell you how much of the effect is due to the treatment.
- This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
- These results apply to the people the trial enrolled: HER2+ early breast cancer: chemotherapy-free trastuzumab + pertuzumab with early 18F-FDG PET response assessment to decide whether chemotherapy is needed. People in a different situation may not see the same effect.
- The trial selected people by a biomarker (HER2); the result should not be assumed for people whose cancer does not have it.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
377 enrolled.
3-year invasive disease-free survival (PET-adapted arm)primary
PET-adapted HP ± chemotherapy95.4 of 100
n = 285
Download
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| 3-year invasive disease-free survival (PET-adapted arm)primary | PET-adapted HP ± chemotherapy | 285 | 95.4% | - | - | link |
Replication
Consistent with WSG-ADAPT HER2+/HR- (pCR-guided de-escalation); phase 3 confirmation pending.