PALLAS & PENELOPE-B
Two large trials found that adding palbociclib after surgery does not prevent recurrence, even though the same drug helps in metastatic disease.
PALLAS (n=5,796): 4-year iDFS 84.2% vs 84.5% (HR 0.96). PENELOPE-B (n=1,250, residual disease after neoadjuvant chemotherapy): iDFS HR 0.93, final OS no difference. Contrasts with abemaciclib (monarchE) and ribociclib (NATALEE); duration, dose intensity, and drug differences are debated.
Setting
Adjuvant palbociclib + endocrine therapy in HR+/HER2- early breast cancer (PALLAS, 2 years; PENELOPE-B, 1 year after residual disease)
Phase
Phase 3
Sponsor
ABCSG / Alliance / GBG / Pfizer
Registry
Headline result
PALLAS iDFS HR 0.96; PENELOPE-B iDFS HR 0.93; both null.
Reported
2020
Enrolled
6862
Replication
Two independent null trials; the positive adjuvant trials used different CDK4/6 inhibitors (monarchE, NATALEE).
In plain words
What these results mean for people, not percentages
4-year invasive disease-free survival (PALLAS)primarysurrogate endpoint
- 84.2 vs 84.5 out of 100 alive without the cancer coming back at 4 years with Palbociclib + ET compared with ET alone; 0.3 fewer per 100.
- On this measure the first group did worse, not better.
- Put another way, the treated group had about 4 percent lower chance of the event at any given time (hazard ratio 0.96, likely range 0.81 to 1.14).
- The likely range for the hazard ratio crosses 1, so the difference could be due to chance.
- 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: Adjuvant palbociclib + endocrine therapy in HR+/HER2- early breast cancer (PALLAS, 2 years; PENELOPE-B, 1 year after residual disease). 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.
6,862 participants enrolled.
4-year invasive disease-free survival (PALLAS)primary
HR 0.96 (0.81–1.14)
Palbociclib + ET84.2 of 100
ET alone84.5 of 100
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| 4-year invasive disease-free survival (PALLAS)primary | Palbociclib + ET | — | 84.2% | 0.96 (0.81–1.14) | — | link |
| ET alone | — | 84.5% |
Replication
Two independent null trials; the positive adjuvant trials used different CDK4/6 inhibitors (monarchE, NATALEE).