# Stephen Johnston

Source: https://onco.cc/people/stephen-johnston/  
OnCo record `stephen-johnston` (Person). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Chief investigator of monarchE, the trial that added abemaciclib to adjuvant endocrine therapy for high-risk early breast cancer.

## Summary

Stephen Johnston led monarchE, which showed two years of abemaciclib with endocrine therapy cuts recurrence in node-positive, high-risk HR-positive early breast cancer, the first adjuvant CDK4/6 inhibitor approval. His earlier work defined mechanisms of endocrine resistance and the fulvestrant dose used today. He continues to lead adjuvant and oral SERD trials from the Royal Marsden.

## Fields

- Kind: Person
- Last checked: 2026-09-10
- Tags: breast; trialist
- Role: Professor of Breast Cancer Medicine, Royal Marsden and Institute of Cancer Research
- Specialisms: HR-positive breast cancer; Adjuvant CDK4/6 inhibition; Endocrine resistance

## Sources

- PubMed: https://pubmed.ncbi.nlm.nih.gov/?term=Johnston%20SRD%5BAuthor%5D%20abemaciclib

## Connected records

- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- technologies: [CDK4/6 inhibitors](https://onco.cc/technologies/cdk46-inhibitor/), [Endocrine therapy (SERMs, AIs, SERDs)](https://onco.cc/technologies/endocrine-therapy/)
- targets: [CDK4/6](https://onco.cc/targets/cdk4-6/), [Estrogen receptor (ERα)](https://onco.cc/targets/estrogen-receptor/)
- drugs: [Abemaciclib](https://onco.cc/drugs/abemaciclib/)
- institutions: [The Institute of Cancer Research](https://onco.cc/institutions/icr-london/), [The Royal Marsden](https://onco.cc/institutions/royal-marsden/)
- trials: [monarchE](https://onco.cc/trials/monarche/)
- key papers: [monarchE: two years of abemaciclib after surgery in high-risk, hormone-receptor-positive early breast cancer](https://onco.cc/key-papers/paper-monarche-jco-2020/)

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