persevERA
An oral SERD did not beat the aromatase inhibitor in first-line treatment when both were combined with palbociclib. Oral SERDs earn their place after resistance, not before it.
Primary endpoint not met (announced 9 March 2026; presented ASCO 2026): investigator-assessed PFS 33.1 months vs 28.2 months, an 11% numerical improvement without statistical significance. The result argues against replacing aromatase inhibitors upfront in unselected patients.
Setting
First-line ER+/HER2- advanced breast cancer: giredestrant + palbociclib vs letrozole + palbociclib
Phase
Phase 3
Sponsor
Roche / Genentech
Registry
Headline result
PFS 33.1 vs 28.2 months, not significant.
Reported
2026
Enrolled
978
Replication
Consistent with the null result of first-line oral SERD strategies without ESR1 selection (e.g., SERENA-4 pending); contrasts with the adjuvant lidERA success.
In plain words
What these results mean for people, not percentages
Progression-free survival (investigator)primarysurrogate endpoint
- Median 33.1 vs 28.2 months with Giredestrant + palbociclib compared with Letrozole + palbociclib; about 4.9 months longer for half the group.
- A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
- 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: First-line ER+/HER2- advanced breast cancer: giredestrant + palbociclib vs letrozole + palbociclib. 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.
978 participants enrolled.
Progression-free survival (investigator)primary
Giredestrant + palbociclib
33.1 mo
Letrozole + palbociclib
28.2 mo
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Progression-free survival (investigator)primary | Giredestrant + palbociclib | — | 33.1 months | — | — | link |
| Letrozole + palbociclib | — | 28.2 months |
Replication
Consistent with the null result of first-line oral SERD strategies without ESR1 selection (e.g., SERENA-4 pending); contrasts with the adjuvant lidERA success.