Synopsis
Select molecularly targeted anticancer treatment only for a validated biomarker and tumour context, manage pathway-specific toxicity and interactions, and distinguish biological resistance from inadequate exposure.
- Targeted therapy inhibits a tumour dependency, receptor, kinase, repair defect or angiogenic pathway; the presence of a biological target does not guarantee clinical benefit.
- The biomarker, assay, specimen, disease stage and licensed or recommended indication must all match before treatment begins.
- Small-molecule inhibitors often have oral absorption, food, acid-suppression and enzyme-interaction issues, while monoclonal antibodies add infusion and immune-mediated risks.
- Class effects include rash, diarrhoea, hypertension, hepatotoxicity and cardiac dysfunction, but toxicity differs substantially by target and agent.
- Baseline ECG, echocardiography, blood pressure, urinalysis, viral testing, eye review or lung assessment is selected from the actual medicine, not applied indiscriminately.
- A correct oral dose still fails when vomiting, non-adherence or interacting medicines reduce exposure; reconcile all prescriptions, supplements and food restrictions.
- Progression can reflect target loss, secondary mutation, bypass signalling, histological transformation or sanctuary-site disease and may justify repeat tissue or circulating DNA.
- Provide explicit hold and emergency rules for severe rash, diarrhoea, breathlessness, chest pain, jaundice, visual change and uncontrolled hypertension.
Key red flags
New pneumonitis, cardiomyopathy, severe hypertension, hepatitis, perforation or ocular injury requires urgent interruption and specialist assessment.
Investigation priorities
Confirm eligibility for the specified targeted medicine.
Management branches
A tumour report identifies a potentially actionable alteration.
- Confirm histology, stage, line, assay and exact biomarker meet the national protocol or access criteria.
- Review organ reserve, interactions, pregnancy and prior toxicities and explain absolute benefit and uncertainty.
- Prescribe through SACT governance with agent-specific baseline tests, supportive medicines and emergency hold instructions.
Cancer worsens after an initial response or stable interval.
- Confirm objective progression and adequate exposure, excluding adherence failure and an imaging mimic.
- Obtain repeat molecular or histological assessment when transformation or a resistance alteration would change therapy.
- Switch, combine, trial or stop treatment according to evidence, organ reserve and goals rather than target presence alone.
Key medicines
Imatinib400 mg orally once daily with a meal and a large glass of water is a common licensed starting dose for chronic-phase BCR::ABL1-positive CML and for unresectable or metastatic KIT-positive GIST; other phases, indications and responses use different protocol doses.Confirm the precise biomarker and indication; monitor full blood count, liver function, oedema, cardiac risk and interactions with CYP3A4 modulators. Adjust or hold only through the disease protocol and product information.
Subcutaneous trastuzumab600 mg subcutaneously every 3 weeks, with no loading dose, for a licensed HER2-positive breast-cancer protocol; intravenous trastuzumab uses a different weight-based schedule and must not be substituted by assumption.Confirm HER2 eligibility and product/formulation, monitor left-ventricular function, and manage injection reactions, pulmonary symptoms and pregnancy risk. Anthracycline sequence materially affects cardiac risk.