When a doctor recommends targeted therapy, many patients are concerned not only about its effectiveness, but also whether side effects will affect their daily life.

Such concerns are very common and form an important part of the treatment process that needs to be addressed.

Principles of Targeted Therapy and Risk Assessment

Targeted therapy is a form of cancer drug treatment that mainly acts on specific receptors or signalling pathways of cancer cells, inhibiting their growth and spread. Compared with chemotherapy, which affects rapidly dividing cells including some normal cells, targeted drugs focus on molecular mechanisms associated with cancer cells.

However, some normal cells in the body may also carry similar receptors or signalling pathways, and therefore side effects may still occur during treatment.

In clinical practice, doctors will conduct careful evaluations before treatment, including disease condition, genetic testing results, and overall health status, in order to formulate an appropriate treatment plan.

It is important to note that “targeted therapy” refers to a broad group of drugs rather than a single treatment. Side effects vary depending on the drug target and drug class. For example, EGFR inhibitors commonly cause rash and diarrhoea; anti-angiogenic drugs may cause high blood pressure, bleeding, or proteinuria; and some targeted therapies may affect liver function, thyroid function, the heart, or the lungs. Actual risks should be assessed according to the specific drug prescribed.

Four Common Side Effects of Targeted Therapy and Daily Management Strategies

Why do targeted drugs cause side effects?

While inhibiting cancer related signals, targeted drugs may also affect the function of normal cells, such as those in the skin, intestines, and vascular system. The occurrence of side effects is related to the drug’s mechanism and does not indicate that the treatment is ineffective.

Common Side Effects and Suggested Responses

The following are examples of side effects that are relatively common or require special attention; not all targeted therapies cause the same reactions.

Side Effect	Common Situations	Daily Management Suggestions	Points to Note
Skin redness and rash	Dryness, itching, rash	Use lukewarm water for bathing, avoid irritating products, increase moisturising. Sun protection is also important. Avoid using steroid or antibiotic creams on your own unless instructed by doctor	Rash spreading or signs of infection
Nausea and diarrhoea	Loss of appetite, increased bowel movements	Eat small frequent meals, avoid greasy and spicy food, maintain hydration	Persistent diarrhoea or dehydration
High blood pressure	Often no clear symptoms	Monitor blood pressure regularly, take medication as prescribed	Persistently high blood pressure or discomfort
Oedema and fatigue	Swelling of limbs or face, ongoing tiredness	Elevate legs, maintain moderate activity, keep regular rest and adequate sleep	Worsening swelling or affecting daily activities

These side effects are relatively common in clinical practice, but their presentation varies depending on individual constitution and type of medication. Some symptoms may be mild initially, but if they continue to worsen—such as expanding rash, frequent diarrhoea, abnormal blood pressure, or swelling affecting mobility—patients should inform their doctor promptly for timely assessment and management.

Treatment Planning and Cost Considerations: Understanding Potential Items Before Treatment for Peace of Mind

Targeted therapy is usually a long term treatment, and its duration varies depending on cancer type, disease progression, and individual health condition. Before starting treatment, understanding the treatment plan and related costs can help patients and families prepare adequately.

When planning a medical budget, in addition to drug costs, attention should also be paid to:

• Genetic testing and imaging examinations

• Regular blood tests and follow up consultations

• Medications or support required for managing side effects

• Additional assessments required due to disease progression

During treatment, some patients may develop drug resistance, meaning cancer cells respond less effectively to the original medication. In such cases, doctors may recommend further genetic testing to identify new mutations, or adjust the treatment plan, such as switching to other drugs or combining therapies. These changes may also affect subsequent treatment arrangements and costs.

Supporting Patients Together: Practical Advice for Caregivers

Side effects during treatment not only bring physical discomfort, but may also affect patients’ emotions and daily routines. Patients may feel anxious or experience mood changes due to ongoing discomfort, changes in appearance, or fatigue.

Caregivers can provide support in the following ways:

• Observe emotional changes and offer companionship and listening

• Help record the timing, frequency, and changes of side effects

• Assist in preparing questions for follow up consultations and discussing management plans with doctors

• Help arrange rest and daily routines when the patient feels fatigued

Appropriate support can reduce anxiety and help the medical team better understand changes in the patient’s condition.

When Should You Contact a Doctor Immediately?

Most side effects can be relieved through careful monitoring and proper management by the medical team. However, if the following situations occur, you should contact your doctor promptly or go to the emergency department immediately:

• Persistent high fever

• Difficulty breathing or shortness of breath

• Severe or persistent diarrhoea or vomiting

• Significant weakness, dizziness, or changes in consciousness

• Rapidly worsening rash or signs of infection

Do not adjust medication dosage or stop treatment on your own—consult your doctor first.

Seek urgent medical advice if you develop chest pain, severe headache or neurological symptoms, blistering or peeling skin, vomiting blood or black stools, markedly reduced urine output, or yellowing of the skin or eyes.

OncoCare：Personalised Treatment Plans with Continuous Side Effect Management

Cancer treatment requires a multidisciplinary approach, from diagnosis to treatment and recovery, with different needs at each stage. Doctors will continuously evaluate and adjust treatment plans based on disease condition, treatment response, and physical status, while monitoring side effects to help patients maintain stability during treatment.

OncoCare brings together experienced oncologists and specialists to provide a range of cancer treatment options, including chemotherapy, radiotherapy, targeted therapy, immunotherapy, and hormone therapy, with coordinated surgical care when needed.

OncoCare’s centres located in Central and Tsim Sha Tsui, offering outpatient and in clinic treatment services in a private and comfortable environment, allowing patients to receive treatment and follow up according to their needs.

Side effects from targeted therapy are not uncommon, but with continuous monitoring and appropriate management, their impact on daily life can often be reduced. Patients are advised to record physical changes and discuss them with their doctors during follow ups. If there are any concerns about treatment or side effects, the medical team can provide suitable guidance.

Targeted Therapy Side Effects FAQ

Q1: Will side effects lessen as the body adapts to targeted therapy?

A: Some patients may find that side effects appearing at the early stage of treatment, such as rash or mild gastrointestinal discomfort, stabilise or reduce over time. However, this does not apply to all side effects. Some conditions may require continuous monitoring or management, such as blood pressure changes or fatigue.

Q2: If side effects are severe, can I reduce the dosage or stop the medication myself?

A: It is not recommended to adjust medication on your own. The dosage and schedule are determined based on disease condition and treatment goals. Unauthorised changes may affect treatment effectiveness or even lead to disease progression.

If side effects affect daily life, consult your doctor as early as possible. The medical team may provide different management approaches, such as supportive medications, dosage adjustment, or temporary treatment interruption under safe conditions.

Q3: Are there any foods that must be strictly avoided during targeted therapy?

A: There are no universal “strictly prohibited” foods for all targeted therapies. However, some oral targeted drugs may interact with grapefruit, pomelo, Seville oranges, St John’s wort, or certain herbal products and supplements. Ask your doctor or pharmacist about food and supplement precautions for your specific medication. Some patients may become more sensitive to greasy, spicy, or highly stimulating foods during treatment, which may cause gastrointestinal discomfort.

Q4: If there are no side effects at all, does it mean the treatment is ineffective?

A: No. The presence or absence of side effects does not directly reflect whether the treatment is working. Different patients may respond very differently to the same medication.

Doctors usually assess treatment effectiveness through imaging, blood tests, or other evaluations, not based solely on side effects.

Q5: Can I use over the counter steroid creams for severe rash?

A: It is not recommended to use medications without proper evaluation. The causes and severity of rashes vary, and some conditions require specific treatments. Using inappropriate products may worsen the skin condition or delay treatment.

Q6: Can I continue working or travel abroad during treatment?

A: Whether you can maintain normal work and daily activities depends on your physical condition, treatment response, and severity of side effects. Some patients can maintain daily routines, while others may require more rest.

If planning travel or prolonged activities, consult your doctor in advance, especially regarding medication schedules, follow up arrangements, and contingency planning.

The health information above has been reviewed by the doctor at OncoCare.