postMONARCH
Continuing CDK4/6 blockade with a different drug after the first one fails gives a small but real benefit.
PFS 6.0 vs 5.3 months (HR 0.73; P=0.017 nominal); the first placebo-controlled phase 3 showing benefit of CDK4/6 inhibition beyond progression. Absolute gain is modest; biomarker-defined subgroups (no ESR1 or PIK3CA mutation) did better.
Setting
HR+/HER2- advanced breast cancer after progression on CDK4/6 + endocrine therapy: abemaciclib + fulvestrant vs placebo + fulvestrant
Phase
Phase 3
Sponsor
Eli Lilly
Registry
Headline result
PFS 6.0 vs 5.3 months, HR 0.73.
Reported
2024
Enrolled
368
Replication
Contrasts with the negative PACE and PALMIRA trials of continuing palbociclib; MAINTAIN (ribociclib switch) was positive in phase 2.
In plain words
What these results mean for people, not percentages
Progression-free survivalprimarysurrogate endpoint
- Median 6 vs 5.3 months with Abemaciclib + fulvestrant compared with Placebo + fulvestrant; about 0.7 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.
- Put another way, the treated group had about 27 percent lower chance of the event at any given time (hazard ratio 0.73, likely range 0.57 to 0.95).
- 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: HR+/HER2- advanced breast cancer after progression on CDK4/6 + endocrine therapy: abemaciclib + fulvestrant vs placebo + fulvestrant. 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.
368 participants enrolled.
Progression-free survivalprimary
HR 0.73 (0.57–0.95) · p = 0.017
Abemaciclib + fulvestrant
6 mo
Placebo + fulvestrant
5.3 mo
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Progression-free survivalprimary | Abemaciclib + fulvestrant | 182 | 6 months | 0.73 (0.57–0.95) | 0.017 | link |
| Placebo + fulvestrant | 186 | 5.3 months |
Replication
Contrasts with the negative PACE and PALMIRA trials of continuing palbociclib; MAINTAIN (ribociclib switch) was positive in phase 2.