# PALLAS & PENELOPE-B

Source: https://onco.cc/trials/pallas-penelope-b/  
OnCo record `pallas-penelope-b` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Two large trials found that adding palbociclib after surgery does not prevent recurrence, even though the same drug helps in metastatic disease.

## Summary

PALLAS and PENELOPE-B, led by trial NCT02513394 and sponsored by ABCSG, the Alliance, the German Breast Group and Pfizer, were two large trials reported in 2020 that found adding palbociclib after surgery does not prevent recurrence in HR-positive, HER2-negative early breast cancer, even though the same drug helps in metastatic disease. PALLAS gave two years of palbociclib with endocrine therapy to 5,796 women and PENELOPE-B gave one year to 1,250 women with residual disease after neoadjuvant chemotherapy, and neither improved invasive disease-free survival, with no survival difference at PENELOPE-B's final analysis. OnCo links them to CDK4/6 as a target, palbociclib, Miguel Martín and the Austrian Breast and Colorectal Cancer Study Group. Whether duration, dose intensity or drug differences explain the split is the open question.

## Fields

- Kind: Trial
- Status: negative
- Last checked: 2026-09-07
- Tags: failure; lesson:drug-not-class
- Registry id: NCT02513394
- Phase: 3
- Setting: Adjuvant palbociclib + endocrine therapy in HR+/HER2- early breast cancer (PALLAS, 2 years; PENELOPE-B, 1 year after residual disease)
- Sponsor: ABCSG / Alliance / GBG / Pfizer
- Enrolled: 6862
- Result: PALLAS iDFS HR 0.96; PENELOPE-B iDFS HR 0.93; both null.
- Outcomes: 4-year invasive disease-free survival (PALLAS): Palbociclib + ET 84.2% vs ET alone 84.5%, HR 0.96
- Replication: Two independent null trials; the positive adjuvant trials used different CDK4/6 inhibitors (monarchE, NATALEE).

## Sources

- ClinicalTrials.gov NCT02513394: https://clinicaltrials.gov/study/NCT02513394

## Connected records

- cancers: [High-risk early HR-positive breast cancer](https://onco.cc/cancers/hr-positive-early-high-risk/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- technologies: [CDK4/6 inhibitors](https://onco.cc/technologies/cdk46-inhibitor/)
- targets: [CDK4/6](https://onco.cc/targets/cdk4-6/)
- drugs: [Palbociclib](https://onco.cc/drugs/palbociclib/)
- companies: [Austrian Breast & Colorectal Cancer Study Group](https://onco.cc/companies/abcsg/)
- people: [Miguel Martín](https://onco.cc/people/miguel-martin/)
- key papers: [Palbociclib with adjuvant endocrine therapy in early breast cancer (PALLAS): interim analysis of a multicentre, open-label, randomised, phase 3 study](https://onco.cc/key-papers/paper-pallas-penelope-b-lancet-oncol-2021/)
- roadmaps: [Hormonal therapy roadmap: removing the ovaries → tamoxifen → oral degraders switched by a blood test](https://onco.cc/roadmaps/hormonal-therapy-roadmap/)

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