Targeted Therapy: Precision medicine for the modern cancer patient.

For many Singaporeans, a cancer diagnosis raises immediate questions about treatment options, side effects, cost, and the possibility of living well during therapy. Targeted therapy has become an important part of modern cancer care because it aims treatment at specific features of cancer cells, rather than attacking all rapidly dividing cells in the body. That difference matters, because cancer is not one disease. It is a group of diseases with different genetic and molecular drivers, and treatment is increasingly guided by the biology of the tumour itself.

In Singapore, patients often receive care through multidisciplinary teams that may include medical oncologists, surgeons, radiation oncologists, pathologists, genetic counsellors, nurses, pharmacists, and allied health professionals. This coordinated approach is essential because targeted therapy is not appropriate for every cancer, and it is usually considered only after the cancer has been tested for certain biomarkers, meaning measurable biological features that help predict whether a treatment may work. For patients and caregivers, understanding how targeted therapy works can make discussions with the oncology team more productive and help set realistic expectations about benefits, risks, and follow-up needs.

Targeted therapy is a cornerstone of precision medicine, a treatment approach that uses information about a person’s tumour, and sometimes the person’s own inherited risk profile, to guide care. It has changed outcomes for some cancers, but it is not a universal cure and it is not interchangeable with immunotherapy or chemotherapy. The right treatment depends on the cancer type, stage, molecular markers, previous treatments, overall health, and patient goals. In Singapore, where cancer care is delivered across public and private systems with strong specialist oversight, patients are increasingly asked to consider molecular testing early so that treatment decisions can be better tailored.

What targeted therapy means in cancer treatment

Targeted therapy refers to drugs that interfere with specific molecules involved in cancer growth, survival, or spread. These molecules may be proteins on the cancer cell surface, enzymes inside the cell, or signals that help tumours form new blood vessels. Because the treatment is directed at a known target, it can sometimes be more precise than traditional chemotherapy. However, “targeted” does not mean side-effect free. These medicines still affect normal tissues that share the same biological pathways, so careful monitoring remains necessary.

The idea behind targeted therapy is straightforward. If a tumour depends heavily on one abnormal pathway, blocking that pathway may slow or stop the cancer. This approach is only useful when the tumour actually has the target. That is why tissue testing, and in some cases blood-based testing, is so important. Without the right biomarker, a targeted drug may offer little benefit while still causing cost and side effects.

How targeted therapy differs from chemotherapy

Chemotherapy works by attacking rapidly dividing cells. Cancer cells divide quickly, but so do some healthy cells, especially those in the hair follicles, digestive tract, and bone marrow. That is why chemotherapy often causes hair loss, mouth sores, nausea, vomiting, and low blood counts. Targeted therapy is designed to act more selectively on cancer-associated pathways, which can reduce some of those classic chemotherapy effects. Still, targeted drugs can cause rash, diarrhoea, liver irritation, blood pressure changes, fatigue, and organ-specific toxicities depending on the medicine.

In practice, some patients receive targeted therapy alone, while others receive it together with chemotherapy, radiotherapy, surgery, or immunotherapy. The goal is to use the most appropriate combination for the tumour biology and the patient’s situation. In Singapore, treatment plans are commonly discussed in tumour boards, where specialists review pathology results, imaging, and molecular testing before recommending a course of action.

What makes a cancer “targetable”

A cancer becomes targetable when testing identifies a feature that can be matched with a specific drug. Common examples include mutations in genes such as EGFR, ALK, or BRAF, or overexpression of a receptor such as HER2. These terms describe abnormalities that help the tumour grow. If a medicine can block that abnormal signal, it may control the disease more effectively than a non-specific treatment.

Not all cancers have established targets, and not all targets are equally actionable. Some molecular findings are associated with approved treatments, while others may only be relevant in clinical trials. This is why pathology and molecular medicine matter so much in modern oncology. A result on a report is useful only if it can be linked to a treatment strategy with evidence behind it.

Common types of targeted therapy and what they do

Targeted therapies are not one class of drug. They include several groups of medicines that work in different ways. Understanding the broad categories helps patients make sense of their prescriptions and the follow-up that accompanies them. The exact drug chosen depends on the cancer type and the biomarker profile of the tumour.

Small molecule inhibitors

Small molecule inhibitors are drugs that enter cancer cells and block enzymes or signalling proteins inside the cell. Many of these medicines end in names that are familiar to oncologists, but patients should focus less on the naming pattern and more on why the drug was chosen. These drugs are widely used in lung cancer, breast cancer, melanoma, gastrointestinal stromal tumours, and other malignancies where a driver mutation or pathway has been identified. They are often taken orally, which can be convenient for patients who are balancing work, family, and follow-up appointments in Singapore’s busy pace of life.

Because they are usually taken at home, adherence matters. Skipping doses, changing timing without advice, or taking them with interacting supplements can affect treatment exposure. Patients should tell their doctors about traditional remedies, herbal supplements, and over-the-counter medicines, since these can alter how the drug is metabolised.

Monoclonal antibodies

Monoclonal antibodies are laboratory-made proteins designed to bind to specific targets on cancer cells or nearby structures. Some block growth signals, some mark cancer cells for immune destruction, and others stop tumours from building blood vessels. These medicines are often given by infusion in hospital or day care settings. They are used in cancers such as HER2-positive breast cancer and certain colorectal cancers, among others.

Because monoclonal antibodies circulate in the bloodstream, infusion-related reactions can occur, especially during the first treatment. Patients may be monitored closely during administration. In Singapore, this usually happens in specialist oncology units that are equipped to manage reactions promptly and safely.

Antibody-drug conjugates and newer precision treatments

Antibody-drug conjugates combine a targeting antibody with a chemotherapy payload. The antibody helps deliver the drug more directly to cancer cells, while the attached payload kills the cell after binding. This design aims to improve efficacy while limiting some damage to healthy tissue. These medicines represent a newer layer of precision oncology and are becoming more important in several cancer types.

Other targeted approaches include angiogenesis inhibitors, which reduce the tumour’s ability to form new blood vessels, and medicines that act on rare molecular alterations. The pace of innovation is rapid, but each new treatment still needs rigorous evidence and specialist judgement before it is used in routine care.

Which cancers in Singapore may use targeted therapy

Targeted therapy is used across many cancers, but the key question is not simply the cancer label. It is whether the tumour has a biomarker that matches a treatment. In Singapore, patients with lung cancer, breast cancer, colorectal cancer, melanoma, certain blood cancers, and some gastrointestinal and kidney cancers may be offered targeted therapy depending on pathology and molecular results. The exact options vary by stage, recurrence risk, prior treatment, and whether the disease has spread.

For example, non-small cell lung cancer is one of the areas where molecular testing is especially important. Many patients may have testing for EGFR, ALK, ROS1, BRAF, MET, RET, NTRK, or other actionable alterations depending on clinical context. In breast cancer, HER2 testing is routine because HER2-positive disease can respond to HER2-directed treatments. In colorectal cancer, testing may help identify patients who may benefit from EGFR-directed therapy or other molecularly guided approaches. These are general patterns, not personal treatment recommendations, and oncologists determine the exact workup based on the cancer subtype.

Why biomarker testing matters before treatment

Biomarker testing can prevent patients from receiving medicines that are unlikely to help. It can also open the door to treatments that would otherwise be missed. Testing may involve immunohistochemistry, fluorescence in situ hybridisation, polymerase chain reaction, next-generation sequencing, or blood-based methods in selected situations. Each test has a different purpose, and not every method is suitable for every cancer.

Singapore’s oncology practice increasingly relies on accurate pathology and molecular profiling to guide treatment selection. Patients should ask whether the cancer tissue has been tested, what biomarkers were assessed, and whether the results will change treatment choices. If a biopsy is small or tissue is limited, the care team may need to prioritise tests based on the most clinically useful targets.

Genetic testing versus tumour testing

Tumour testing looks at the cancer itself. Genetic testing looks for inherited changes that a person may carry in all cells of the body. These are different. A tumour may have a mutation that is not inherited, while an inherited mutation may increase cancer risk for the patient and family members. In some cases, inherited testing can affect future screening, prevention, and family counselling. Genetic counselling is especially relevant when there is a strong family history of cancer, young age at diagnosis, or tumour features that suggest an inherited syndrome.

Patients often find this distinction confusing, but it is important. A tumour result may explain why a drug works, while inherited testing may explain why the cancer occurred or whether relatives should consider assessment. Both play a role in precision medicine, but they answer different questions.

Benefits, limitations, and side effects patients should understand

Targeted therapy can offer meaningful benefits, including better tumour control in selected patients, fewer traditional chemotherapy effects for some regimens, and the possibility of oral treatment at home. In some cancers, targeted therapy can turn a once rapidly progressive disease into a longer-term chronic condition that is managed over time. That said, these outcomes depend on the cancer biology and the patient’s overall condition. The treatment is not guaranteed to work, and resistance can develop.

Resistance means the cancer finds another way to grow despite treatment. This can happen through additional mutations, activation of alternative pathways, or changes in the tumour microenvironment. When resistance appears, oncologists may repeat testing, switch medicines, combine therapies, or consider a clinical trial if appropriate. This is one reason follow-up is so important.

Common side effects

Side effects vary widely by drug, but common issues include skin rash, diarrhoea, mouth sores, tiredness, liver enzyme changes, blood pressure elevation, hand-foot syndrome, and changes in heart function for selected drugs. Some therapies require regular blood tests, heart scans, blood pressure checks, or eye examinations. Patients should not assume that because a drug is “targeted” it is automatically gentle. Some targeted medicines have serious but specific toxicities that need early detection.

If a patient develops severe diarrhoea, fever, shortness of breath, chest pain, swelling, sudden weakness, or an extensive rash, prompt medical attention is necessary. Mild side effects should also be discussed early, because supportive care can often make treatment much more tolerable. In Singapore, where many patients manage work, caregiving, and treatment simultaneously, it is helpful to plan medication routines and follow-up visits around daily obligations to reduce missed doses and delays in care.

Drug interactions and lifestyle considerations

Targeted therapy can interact with acid-reducing medicines, anticonvulsants, antibiotics, antifungals, and herbal products. Patients should bring an updated medication list to every appointment, including supplements and traditional remedies. Timing with food may also matter for certain drugs. Travel, fasting, changes in appetite, or digestive symptoms can all affect how the medicine is taken and absorbed.

For patients in Singapore, practical planning helps. If oral therapy is prescribed, set reminders on the phone, use a weekly pill organiser if appropriate, and know who to contact if a dose is missed or vomiting occurs after taking the medicine. If infusion therapy is given, arrange transport in advance and check whether any pre-treatment blood tests or scans are needed before the visit.

How targeted therapy fits into cancer care in Singapore

Singapore’s cancer care environment is well suited to precision medicine because specialist services, pathology support, molecular diagnostics, and advanced imaging are widely integrated into oncology practice. Patients may be treated at public restructured hospitals, private specialist centres, or through a combination depending on referral pathways and insurance coverage. Regardless of setting, the principles are the same, treatment should be based on evidence, tailored to the tumour, and monitored carefully.

Access and cost are practical concerns for many families. Some targeted therapies are expensive, and coverage depends on the drug, indication, eligibility, and payment pathway. Patients should ask the oncology team and hospital financial counsellors about the likely treatment plan, what tests are needed before starting, and whether any prior approvals are required. Clear planning helps reduce delays between diagnosis and treatment start.

Questions to ask the oncology team

• What biomarker or mutation is this treatment targeting?
• Was the tumour tested for all relevant markers?
• What benefit can reasonably be expected in my cancer type?
• What side effects should I watch for at home?
• How often will I need blood tests, scans, or heart monitoring?
• Are there food, supplement, or drug interactions I should avoid?
• What are the options if this treatment stops working?

These questions help patients take part in shared decision-making. They also create a better understanding of why one treatment is preferred over another, especially when multiple options exist.

Targeted therapy represents one of the most important advances in cancer treatment because it turns tumour biology into a guide for care. For Singapore patients, the main takeaway is not that every cancer can be treated this way, but that molecular testing may uncover a more precise option than traditional one-size-fits-all treatment. If you or a family member is facing a cancer diagnosis, ask whether the tumour should be tested for actionable markers, whether a genetic counsellor is appropriate, and how the recommended treatment fits into daily life, work, and family responsibilities. The most useful cancer plan is the one that is scientifically sound, personally realistic, and closely supervised by an experienced oncology team.

Medical note: This article is for general education only and does not replace an assessment by a qualified doctor. Cancer treatment should always be discussed with an oncologist who can interpret test results in the context of the individual patient.