PALOMA-2
The trial that made palbociclib the first CDK4/6 inhibitor in routine use. It doubled progression-free time but did not extend life.
PFS 27.6 vs 14.5 months (HR 0.56). Final OS 53.9 vs 51.2 months (HR 0.96), no significant benefit, with substantial missing survival data. Together with PALOMA-3 (OS HR 0.81, NS) this differentiates palbociclib from ribociclib and abemaciclib on survival.
Setting
First-line postmenopausal HR+/HER2- advanced breast cancer: palbociclib + letrozole vs placebo + letrozole
Phase
Phase 3
Sponsor
Pfizer
Registry
Headline result
PFS HR 0.56; OS HR 0.96 (NS).
Reported
2016
Enrolled
666
Replication
PFS effect replicated across all CDK4/6 trials; absence of OS benefit replicated in PALOMA-3 and the adjuvant PALLAS/PENELOPE-B trials.
In plain words
What these results mean for people, not percentages
Progression-free survivalprimarysurrogate endpoint
- Median 27.6 vs 14.5 months with Palbociclib + letrozole compared with Placebo + letrozole; about 13.1 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 44 percent lower chance of the event at any given time (hazard ratio 0.56, likely range 0.46 to 0.69).
- 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.
Overall survivalsurvival endpoint
- Median 53.9 vs 51.2 months with Palbociclib + letrozole compared with Placebo + letrozole; about 2.7 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 4 percent lower chance of the event at any given time (hazard ratio 0.96, likely range 0.78 to 1.18).
- The likely range for the hazard ratio crosses 1, so the difference could be due to chance.
- Overall survival counts deaths from any cause, so it is the most direct measure of whether a treatment helps people live longer.
Be careful
- These results apply to the people the trial enrolled: First-line postmenopausal HR+/HER2- advanced breast cancer: palbociclib + letrozole vs placebo + letrozole. 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.
666 participants enrolled.
Progression-free survivalprimary
HR 0.56 (0.46–0.69)
Palbociclib + letrozole
27.6 mo
Placebo + letrozole
14.5 mo
Overall survival
HR 0.96 (0.78–1.18)
Palbociclib + letrozole
53.9 mo
Placebo + letrozole
51.2 mo
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Progression-free survivalprimary | Palbociclib + letrozole | 444 | 27.6 months | 0.56 (0.46–0.69) | — | link |
| Placebo + letrozole | 222 | 14.5 months | ||||
| Overall survival | Palbociclib + letrozole | — | 53.9 months | 0.96 (0.78–1.18) | — | — |
| Placebo + letrozole | — | 51.2 months |
Replication
PFS effect replicated across all CDK4/6 trials; absence of OS benefit replicated in PALOMA-3 and the adjuvant PALLAS/PENELOPE-B trials.