DRUG RESISTANCE IN
TARGETED THERAPY
Resistance does not close the door on targeted therapy. It changes which door is open. Molecular testing at progression is what identifies which one.
analyticsAt a Glance
- check_circleAcquired resistance is the most common reason targeted therapy stops working over time
- check_circleResistance mechanisms include secondary mutations (e.g. T790M in EGFR) and bypass pathway activation
- check_circleLiquid biopsy and rebiopsy at progression are essential to understand the resistance mechanism
- check_circleNext-generation drugs (osimertinib, lorlatinib) are designed to overcome specific resistance mutations
How Resistance Develops
Understanding the specific resistance mechanism changes the next treatment decision. Different mechanisms require different responses.
On-Target Resistance Mutations
A new mutation in the same gene the drug was targeting alters the binding site so the drug can no longer attach. The T790M mutation in EGFR-mutant lung cancer is the classic example -- it drove development of osimertinib specifically to overcome it.
Off-Target Bypass Mechanisms
The tumour activates an alternative pathway that bypasses the one the drug was blocking. MET amplification in EGFR-mutant NSCLC is an example -- the cancer finds a different route to the same growth destination.
Histologic Transformation
In some cases the tumour changes its cell type under treatment pressure. EGFR-mutant NSCLC occasionally transforms to small cell lung cancer at resistance, requiring a completely different treatment approach.
Target Amplification
The tumour produces so much of the targeted protein that the drug can no longer block it effectively at standard doses. Requires dose escalation or switching to an agent with different binding characteristics.
Frequently Asked Questions
How CancerFax Helps
CancerFax is a specialist cancer access and patient-navigation platform. We help patients and families understand their options, organise medical records, coordinate hospital communication, and support cross-border treatment planning where appropriate.
We help collect and organise reports, scans, pathology, biomarker results, and treatment history for structured case review.
We communicate with hospitals or trial teams to assess whether a case may be suitable for further screening.
We support appointment coordination, document submission, translation, and direct communication with international departments.
For international patients, we help with practical coordination — travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
From inquiry through to follow-up, our coordinators provide a single point of contact for the family.
CancerFax does not guarantee treatment access, eligibility, or clinical outcome. Our role is to help patients access accurate information, structured review, and appropriate specialist pathways.
Questions About Resistance to Your Targeted Therapy?
CancerFax reviews your progression workup and connects you with oncologists experienced in identifying and addressing targeted therapy resistance mechanisms.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified oncologist before making treatment decisions.