Targeted Therapy

Targeted therapy is a cancer treatment that uses drugs designed to attack specific molecules (proteins or genes) that help cancer cells grow, divide, and spread — while leaving healthy cells largely alone.

Unlike standard chemotherapy, which acts broadly on all fast-dividing cells, targeted therapy works like a guided key searching for a specific lock on cancer cells. When the drug finds and blocks that target — for example, a protein called a receptor (a docking site on the cell surface) or an enzyme (a protein that drives cell growth) — it can stop the cancer cell from getting the signals it needs to survive. Some targeted drugs also work by cutting off the blood supply that feeds a tumour, or by tagging cancer cells so the body's own immune system can destroy them.

Targeted therapy is used when a patient's tumour has been shown — through molecular testing (laboratory analysis of the tumour's genes and proteins) — to carry a specific change that a targeted drug can act on. It is used across many cancer types, most commonly when the cancer has spread or has not responded to other treatments, but also sometimes as a first-line treatment (the first treatment given) or alongside other therapies.

• Non-small cell lung cancer (NSCLC) — especially when a mutation (change) in genes such as EGFR, ALK, or ROS1 is found
• Breast cancer — particularly HER2-positive breast cancer, where tumour cells carry too many copies of the HER2 protein
• Colorectal cancer (cancer of the large intestine) — when specific gene mutations such as KRAS, NRAS, or BRAF are identified
• Chronic myeloid leukaemia (CML) — a blood cancer driven by a specific gene abnormality called the BCR-ABL fusion
• Gastrointestinal stromal tumours (GIST) — tumours of the digestive tract that often carry a KIT or PDGFRA gene mutation
• Thyroid cancer, kidney cancer, liver cancer, and certain melanomas (skin cancers) with identifiable molecular targets
• Some cases where standard chemotherapy has stopped working and molecular testing reveals a targetable change

Targeted therapy is not suitable for every cancer patient. If molecular testing shows the tumour does not carry the specific target that a drug acts on, that drug will not work and is not recommended. There are also situations where other factors make it unsuitable.

• Tumours with no identifiable molecular target after thorough testing
• Severe liver or kidney impairment, which may prevent the body from processing the drug safely
• Certain heart conditions, as some targeted drugs can affect heart function
• Pregnancy, because most targeted drugs carry risks to the developing baby
• Known severe allergy to the specific drug or its components

Targeted therapy generally causes fewer widespread side effects than standard chemotherapy, but it is not without risks — the specific side effects depend on which drug is used and which molecule it targets.

• Skin problems — rash, dryness, or acne-like spots, which are common with drugs that target a protein called EGFR
• Diarrhoea (loose, frequent stools) — often mild but sometimes severe enough to need treatment
• Fatigue (persistent tiredness) that can affect daily activities
• High blood pressure — particularly with drugs that block tumour blood vessel growth (anti-angiogenic agents)
• Nausea (feeling sick) and loss of appetite
• Liver stress — some targeted drugs raise liver enzyme (a chemical marker of liver health) levels in blood tests, though this is often reversible
• Slow wound healing — important to mention before any planned surgery
• Heart function changes — including reduced pumping strength, seen mainly with certain drugs used in breast cancer
• Blood clotting problems — either an increased risk of clots or, less commonly, increased bleeding
• Peripheral neuropathy (tingling or numbness in the hands or feet) — with some drug types
• Eye problems such as dry eyes or, rarely, vision changes — depending on the drug
• Drug resistance (cancer cells changing so the drug no longer works) — not an immediate side effect, but a recognised challenge over time

Before targeted therapy begins, the oncology team (cancer specialists) carry out a series of tests to confirm that the patient's tumour has the right molecular target, and to check that the body is well enough to receive the treatment. This preparation phase can take days to weeks, depending on the test results.

Patients are usually asked to share a full list of all medicines, vitamins, and herbal supplements they take, because some can interact with targeted drugs. The team will advise whether any should be paused. Smoking can affect how some drugs are processed in the body, so the medical team will often discuss stopping. Alcohol should usually be limited. Fasting is generally not required before most targeted therapy doses, but the medical team will give specific instructions if it is needed.

Tests typically run before starting targeted therapy include:

• Molecular or genomic testing (biomarker testing) — a biopsy (small tissue sample) or, in some cases, a liquid biopsy (blood test) is used to identify specific gene mutations or protein changes in the tumour
• Blood tests to check liver function, kidney function, and blood cell counts
• Heart function test such as an echocardiogram (ultrasound of the heart) or EKG (a recording of the heart's electrical activity), especially for drugs known to affect the heart
• Blood pressure measurement
• Imaging scans — CT, MRI, or PET scan — to document the size and location of the tumour before treatment starts, so progress can be measured later

Once the tests confirm suitability, targeted therapy is given in one of several ways, depending on the specific drug:

• 1. Oral tablets or capsules — the most common form; the patient takes a pill at home on a daily or twice-daily schedule set by the oncologist
• 2. Intravenous (IV) infusion — the drug is given through a drip into a vein, usually in a hospital day clinic or infusion centre; the patient sits or reclines during the infusion, which can last from under an hour to several hours depending on the drug
• 3. Subcutaneous injection — some targeted drugs are injected just under the skin, often at the clinic
• 4. During the infusion or after taking the first dose, staff monitor the patient for any immediate reaction such as flushing, rash, or difficulty breathing (called an infusion reaction), especially on the first treatment session

Targeted therapy is usually given over a long period — months or sometimes years — so aftercare is an ongoing process rather than a single recovery phase. The exact follow-up schedule depends on the drug, the cancer type, and how well the treatment is working. Most patients continue to live at home and visit the hospital or clinic regularly for monitoring.

• Regular blood tests — usually every few weeks at first, then less often — to check liver function, kidney function, blood pressure, and blood cell counts
• Repeat imaging scans (CT, MRI, or PET) at intervals set by the oncologist, to measure how the tumour is responding to treatment
• Skin care: for patients on drugs that commonly cause skin reactions, the team will usually advise gentle moisturisers, sun protection, and prompt reporting of any severe rash
• Blood pressure monitoring at home may be recommended for patients on drugs that raise blood pressure, with regular check-ins at the clinic
• Heart monitoring: repeat echocardiogram or EKG checks at scheduled intervals for drugs that can affect heart function
• Reporting new or worsening symptoms promptly — particularly unusual bruising or bleeding, sudden swelling, chest pain, shortness of breath, or severe diarrhoea — so the team can decide whether the drug dose needs to be adjusted or paused
• Wound care awareness: if any surgical procedure is planned during treatment, the surgical team must be informed, because some targeted drugs slow wound healing and may need to be paused beforehand
• Contraception (birth control): the oncology team will usually advise reliable contraception during treatment and for a period afterwards, because most targeted drugs are harmful to a developing baby
• Lifestyle: a balanced diet, gentle physical activity as tolerated, and avoiding smoking are generally encouraged, though the patient's individual capacity will guide this
• Psychological support: living with ongoing cancer treatment can be stressful; many hospitals offer counselling or support groups, and patients are encouraged to ask about these services