# Stop excluding brain metastases from cancer trials

Source: https://onco.cc/ideas/idea-bio2-cns-cohort-mandate/  
OnCo record `idea-bio2-cns-cohort-mandate` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

One in five people with advanced cancer has brain spread, yet most trials refuse them. Requiring brain cohorts would give those patients evidence instead of guesswork.

## Summary

Brain metastasis exclusion criteria persist by habit, and regulators and professional bodies have issued guidance encouraging inclusion of patients with stable treated brain metastases. Making a CNS cohort with CNS-specific response endpoints a default expectation for registrational trials in CNS-tropic cancers, unless justified otherwise, would generate labelled intracranial data rather than post-approval retrospectives.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: A default-inclusion policy raises the proportion of new oncology approvals with intracranial activity data in the label from a minority to over half within five years, without slowing accrual.
- Rationale: Inclusion of patients with treated brain metastases has been feasible where sponsors have tried it, and the resulting intracranial data changed practice in HER2-positive breast cancer and ALK-positive lung cancer. The barrier is convention and risk aversion, not science.
- Proposed test: Audit exclusion criteria in the last 200 registrational oncology protocols, publish the rate, then have one regulator or cooperative group adopt default CNS cohorts for CNS-tropic diseases and measure accrual, safety and labelling outcomes.
- Maturity: speculative
- Actor: regulator

## Sources

- ASCO-Friends eligibility criteria work: https://www.asco.org

## Connected records

- institutions: [American Society of Clinical Oncology (ASCO)](https://onco.cc/institutions/asco/), [European Society for Medical Oncology (ESMO)](https://onco.cc/institutions/esmo/)
- terms: [HER2-positive brain metastases](https://onco.cc/terms/her2-brain-metastases/)
- trials: [ALINA](https://onco.cc/trials/alina/), [HER2CLIMB](https://onco.cc/trials/her2climb/)
- bottlenecks: [The brain: barrier and sanctuary](https://onco.cc/bottlenecks/b-brain-delivery/), [Trial design, endpoints and cost](https://onco.cc/bottlenecks/b-trial-design/), [Trials enrol too few, too slowly](https://onco.cc/bottlenecks/b-trial-enrolment/)

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