MAPK Pathway Resistance: A Framework for Reading Resistance Reports

Resistance Is a Network Problem

A therapy can suppress one dependency while tumour cells retain or acquire routes around it. In the MAPK network, those routes may sit at the receptor, RAS, RAF or downstream levels.

The same broad pattern can arise through different specific alterations. A pathway label therefore provides a starting framework, not a substitute for variant-level evidence.

Why Samples Can Differ

A tumour is made of evolving cell populations. A later tissue sample may capture one lesion, while circulating tumour DNA may capture DNA shed from several sites but miss low-shedding disease.

Differences between baseline and progression results can reflect biology, sampling and assay sensitivity. Review should include sample timing, coverage and whether a finding is newly detected or simply newly measured.

Key Takeaways

• ·MAPK resistance can arise through target changes, bypass routes or downstream reactivation.
• ·More than one resistance-associated alteration may coexist.
• ·Sample type and timing influence what a report can show.