OnCo
trialsTrialNegative

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).

Outcomes

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In plain words
What these results mean for people, not percentages
6,862 people took part
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
Source
EndpointArmnValueHR (95% CI)pSource
4-year invasive disease-free survival (PALLAS)primaryPalbociclib + ET84.2%0.96 (0.81–1.14)link
ET alone84.5%
Replication
Two independent null trials; the positive adjuvant trials used different CDK4/6 inhibitors (monarchE, NATALEE).

Connected

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