What targeted therapy is
Cancers grow because of specific changes in their cells — a mutation in a gene such as EGFR or ALK in some lung cancers, over-expression of the HER2 protein in some breast and stomach cancers, a BRAF mutation in some melanomas, the BCR-ABL fusion in chronic myeloid leukaemia, and many others. Targeted therapies are drugs designed to block that specific driver. Some are tablets (small-molecule inhibitors), some are antibodies given as a drip, and some are antibodies linked to a chemotherapy payload (antibody–drug conjugates).
Because they act on a defined target, they are usually more selective than chemotherapy — but "targeted" does not mean free of side effects, and the drug only helps if your cancer actually carries the target.
Testing comes first
The decision starts in the pathology laboratory. Depending on the cancer, tests on the biopsy (or sometimes on a blood sample — a "liquid biopsy") look for the relevant markers: for example EGFR, ALK, ROS1, KRAS, BRAF, MET and RET in lung adenocarcinoma; HER2, ER and PR in breast cancer; RAS and BRAF in colorectal cancer; BRCA in some breast, ovarian, prostate and pancreatic cancers.
If your biopsy report does not mention these tests, ask whether they have been done or whether the tissue can be sent for them. Sometimes there is not enough tissue and a repeat biopsy is worth it — the result can change the entire plan.
When targeted therapy is considered
- As first treatment for advanced cancer with a known driver — for example EGFR-mutant lung cancer, where a tablet is usually preferred over chemotherapy as the first step.
- Alongside chemotherapy — for example HER2-targeted antibodies with chemotherapy in HER2-positive breast cancer.
- After surgery — in some settings to reduce the risk of recurrence.
- When a cancer has become resistant to an earlier drug and testing shows a new target.
Targeted therapy is rarely used "just in case": without the target, it adds cost and side effects and no benefit.
What to expect
Tablets are taken daily at home with regular clinic visits and blood tests; antibody treatments are given as a drip every one to three weeks. Response is usually assessed with scans after two to three months. Many patients continue for as long as the drug keeps working and is tolerated — sometimes years — and switch when the cancer develops resistance.
Side effects
They vary widely by drug. Common ones include skin rash and dryness, diarrhoea, mouth soreness, tiredness, changes in liver tests or blood pressure, and — with some drugs — effects on the heart, lungs or eyes that are monitored with specific tests. Most are manageable with dose adjustment and supportive care; tell your team early rather than stopping the drug on your own.
Questions worth asking
- Which molecular tests were done on my biopsy, and what did they show?
- Is there a targeted drug for my result, and what is the evidence for it in my cancer and stage?
- How is it taken, how often will I need tests, and what will they look for?
- What happens if the cancer stops responding — are there next options?
- Are there generic or lower-cost versions with the same evidence, and what does treatment realistically cost per month?
Preparing for your consultation
Bring the full biopsy/histopathology report including any immunohistochemistry and molecular results, scans with reports, and a note of all previous treatments with dates. If a molecular test was done at another laboratory, bring the original report rather than a summary.