Hossam Abdulkhalek, Regional Adviser at Royal College of Physicians, shared on LinkedIn:
“postMONARCH at ESMO 2026: Interesting data, but does it change practice in the UK?
The final overall survival analysis from the Phase III postMONARCH trial, evaluating abemaciclib plus fulvestrant after progression on a prior CDK4/6 inhibitor and endocrine therapy in HR+/HER2- advanced breast cancer.
The headline result was an overall survival difference of 32.1 months vs 24.6 months (7.5 months), favouring abemaciclib plus fulvestrant. However, the study did not reach statistical significance for OS.
So what should we make of this?
Reasons for optimism:
- The OS trend is directionally consistent with the previously reported PFS benefit.
- Benefits appeared broadly consistent across predefined subgroups.
- The study supports the biological rationale for continuing CDK4/6 pathway inhibition beyond progression
- Importantly, it offers a chemotherapy-delaying strategy for some patients.
The UK real-time practice
While these results are scientifically interesting, translating them into UK practice is not straightforward.
In the NHS, the treatment landscape has evolved significantly since postMONARCH was designed:
- Increasing use of molecularly guided treatment strategies.
- Availability of targeted agents for selected patients, including AKT and PI3K pathway-directed therapies.
- Growing adoption of ESR1 testing and selective estrogen receptor degraders where available.
- Greater emphasis on genomic profiling to personalize sequencing decisions.
As a result, the comparator of ‘fulvestrant alone after CDK4/6 progression‘ may not fully reflect contemporary UK practice for many patients.”
You can also read: postMONARCH: Abemaciclib Shows Numerically Longer Overall Survival After Prior CDK4/6 Inhibition
