Ado-trastuzumab emtansine (Kadcyla)

At a glance

Trastuzumab emtansine (Kadcyla) is an antibody–drug conjugate, often shortened to ADC. It combines an antibody that recognises a target on cells with a cell-killing medicine. It is given by a trained team through a drip into a vein. Although it is targeted treatment, it can affect healthy tissues and needs careful monitoring.

Kadcyla combines HER2-targeted treatment with a cell-killing payload. Liver tests, platelet counts and heart-function monitoring are central to care. It is not interchangeable with ordinary trastuzumab or with trastuzumab deruxtecan, and its dose must not be copied from either medicine.

Follow your own treatment calendar and the advice from your care team. Keep your medicine names and treatment dates handy to share with other clinicians.

How it works

The trastuzumab antibody recognises HER2 on the cell surface. It carries DM1, also called emtansine, which disrupts the internal structures needed for cell division after entering the cell. The antibody also has HER2-directed actions. Combining them into one ADC creates a distinct medicine with its own dose and safety profile.

The antibody, its chemical link and the attached medicine form one product. They are not separate medicines that you can take in different amounts yourself. Targeting helps deliver treatment to particular cells, but it does not mean that only cancer cells are affected. Side effects can come from the attached medicine, the antibody, your existing illness or accompanying treatment.

An ADC is different from an immune checkpoint inhibitor, even when both are given in the same treatment plan. A reaction or noticeable side effect is not proof that an ADC is working. Equally, having few side effects does not mean that treatment has failed.

Is this treatment suitable for me?

Kadcyla treats selected HER2-positive breast cancers. It may be used after surgery when invasive cancer remains following preoperative taxane chemotherapy and HER2-directed treatment. European guidance uses this prior-treatment description; US guidance specifically names taxane and trastuzumab-based treatment. Your team checks the applicable regional criteria. It is also used for selected advanced breast cancers after previous trastuzumab and a taxane, including cancer that returns during or soon after earlier treatment. Your oncologist checks the exact treatment setting and previous medicines before recommending it.

Validated testing confirms the relevant HER2-positive finding. The team considers prior treatment, the treatment goal, heart function, liver health, platelet count and nerve symptoms. HER2-low or a gene mutation should not simply be treated as equivalent to the HER2-positive criteria used for a Kadcyla plan.

The discussion should cover the aim of treatment, the alternatives, likely appointments and how benefit will be assessed. A target found in a sample is one part of this decision; it does not guarantee a response. Tell the team what matters to you, including independence, work, caring responsibilities and the practical support available at home.

Before treatment

Bring a complete list of prescribed and non-prescribed medicines, vitamins, herbal products and allergies. Mention previous difficult reactions to infusions, infections, diabetes, liver or kidney problems and any pregnancy or breastfeeding. Explain symptoms you already have so a later change is easier to recognise.

Blood counts, especially platelets, and liver tests are checked. An echocardiogram or another appropriate test measures heart pumping function. Tell the team about previous heart disease, anthracycline treatment, liver disease, bleeding or anticoagulant use. Existing tingling and numbness should be recorded. A pregnancy test is needed before treatment if you could become pregnant. Tell the team specifically if trastuzumab was permanently stopped because of an infusion reaction or allergy; Kadcyla is not recommended in that situation.

A nurse or pharmacist should explain the supportive medicines and which ones start before the treatment day. Ask your team to help you plan when to take each medicine. Make sure you know how to reach your hospital's urgent oncology service outside clinic hours. You may find it helpful to save the instructions on your phone or keep a copy at home. A family member or friend can help you remember them.

Discuss fertility preservation before treatment if future parenthood matters to you. Tell the team about dental problems and planned procedures. A procedure may need to be timed around blood counts and infection risk. Do not postpone reporting an active dental infection while waiting for the next routine appointment.

How treatment is given

The usual dose is 3.6 mg/kg as an intravenous infusion every three weeks. The postoperative course for residual invasive early breast cancer is usually 14 cycles unless recurrence or side effects require stopping. Advanced-disease treatment continues according to benefit and tolerance. The first infusion takes 90 minutes, with observation during and for at least 90 minutes afterwards. If tolerated, later infusions may take 30 minutes, with at least 30 minutes of observation afterwards.

Kadcyla is not given as a rapid intravenous injection and should not be confused with a subcutaneous trastuzumab product. Premedicines are selected according to the hospital plan and any previous reaction. Dose reductions or delays may be needed for platelet, liver, nerve or other problems. The team should explain the reason and give you a revised calendar.

The medicine label and prescription should show the full name trastuzumab emtansine or the relevant US form, ado-trastuzumab emtansine. If you hear only the word trastuzumab, it is reasonable to check which product is intended before administration.

Treatment is delivered through a cannula in a vein, a central line or an implanted port, depending on the plan and available access. Staff check the medicine, your identity, blood results and recent symptoms before starting. The appointment includes preparation and monitoring, so it will usually take longer than the infusion itself.

Tell the nurse immediately if you notice burning, pain, swelling, redness, leakage or tightness around the infusion site. These can mean medicine is leaking outside the vein. Do not wait for the drip to finish. At home, report a site that becomes more painful, blistered or discoloured, even if it looked normal when you left.

Also report flushing, itching, shivering, chest or back discomfort, wheezing, dizziness or swelling during treatment. Staff can stop or slow the infusion and assess you. Do not adjust the pump or line yourself. If a line remains in place, follow its cleaning and dressing instructions and report fever, tenderness or drainage around it.

If an appointment is missed, contact the treatment unit to arrange the next dose. Do not simply wait for the following cycle or seek an extra dose elsewhere. The correct restart date depends on why the dose was missed, the treatment schedule and recovery from side effects.

Monitoring your treatment

Blood tests usually check infection-fighting cells, red cells, platelets, kidney function and liver function. Some abnormalities cause no early symptoms. A reassuring blood test does not make a new symptom safe to ignore, and feeling well is not a reason to miss monitoring.

Platelet counts and liver tests are checked before each dose. Heart function is assessed before treatment and regularly during it, often around every three months according to the plan. The team asks about bleeding, neuropathy and breathing symptoms. Response assessments depend on the treatment goal; toxicity monitoring is needed even when there is no measurable disease to follow on a scan.

Your team compares examinations, symptoms and relevant scans or disease tests over time. Ask when the first response assessment is planned and what the result could change. A treatment break or lower dose may protect you from accumulating harm while allowing further treatment. It is not automatically evidence that the cancer has worsened. Never try to compensate for a reduced dose with supplements or closer appointments.

Common side effects

Side effects vary between people and between treatment combinations. You may experience several, a few or none of those described. Tell the team about symptoms that interfere with eating, sleeping, walking or usual tasks; a problem does not need to be severe before support is worthwhile.

Bruising and bleeding

Platelets can fall, sometimes without symptoms. Report easy bruising, gum bleeding, nosebleeds or tiny red-purple spots. Follow repeat-test instructions and avoid starting aspirin or anti-inflammatory painkillers without checking. Significant bleeding can occasionally occur even without a very low platelet count.

Nerve symptoms and aches

Tingling, numbness or burning may affect fingers and toes. Tell the team about weakness, balance changes or difficulty with buttons. Severe neuropathy requires a treatment pause until it improves, as assessed by your team. Muscle or joint pain and headache can also occur. Ask which pain relief is suitable, particularly if liver tests or platelets are abnormal.

Digestive symptoms and fatigue

Nausea, constipation, dry mouth or mouth discomfort may affect intake. Use the supportive-care plan and ask for help early. Fatigue may build through the course; pace activity, but report sudden weakness or breathlessness because these can have treatable causes.

Tiredness and reduced stamina

Plan important tasks for the part of the day when you have most energy and accept practical help. Short periods of gentle activity can be useful, with rest between them. Sudden marked weakness, breathlessness, dizziness or a racing heart needs assessment for causes such as anaemia, infection or dehydration. Do not assume every new limitation is ordinary treatment fatigue.

Nausea, appetite and bowel changes

Take prescribed anti-sickness medicines on the agreed schedule. Small regular meals, cool foods and frequent sips can be easier to manage. Tell the team if you cannot keep medicines or fluids down, are passing little urine or are losing weight. A dietitian can help when eating becomes difficult.

Record loose stools and whether there is pain, blood or fever. Severe diarrhoea, repeated vomiting or a swollen painful abdomen needs prompt advice. Constipation can be worsened by anti-sickness drugs and pain relief; use the bowel plan your team recommends. Do not repeatedly add laxatives or anti-diarrhoeal medicines without checking when there is significant pain or other new illness.

Low blood counts

A low white cell count can make infection progress quickly. Follow the urgent-help instructions below. Low red cells can cause tiredness, pallor or breathlessness; sometimes transfusions are needed. Low platelets can cause easy bruising, nosebleeds, bleeding gums or tiny red-purple spots. Report new bleeding and avoid starting aspirin or anti-inflammatory painkillers without checking. Do not stop a prescribed blood thinner yourself; the team must balance bleeding and clotting risks.

Mouth comfort and skin care

Use a soft toothbrush and the mouth-care products advised by your team. Report ulcers, white patches or soreness that limits eating, because infection or dehydration may need treatment. Avoid very hot, acidic or spicy foods if they sting. Moisturise dry skin with a simple fragrance-free product and protect it from strong sunlight. Painful skin, blisters or rapidly worsening redness need medical assessment rather than a new cosmetic product.

Important side effects

Liver injury

Kadcyla can cause serious liver toxicity. Blood tests may change before symptoms develop. Report jaundice, dark urine, right upper abdominal pain or unusual severe fatigue. Rarely, nodular regenerative hyperplasia can alter the liver’s structure and cause high pressure in its blood vessels. New abdominal swelling or gastrointestinal bleeding requires assessment even when earlier liver-enzyme results were not markedly abnormal. Confirmed nodular regenerative hyperplasia requires the treating team to stop Kadcyla permanently.

Heart dysfunction and lung inflammation

Reduced pumping function can cause breathlessness, ankle swelling, rapid weight gain or difficulty lying flat. Lung inflammation, including pneumonitis, can also occur; radiation-related pneumonitis may be relevant in a combined treatment plan. New cough or breathlessness needs prompt review. Confirmed treatment-related interstitial lung disease or pneumonitis requires permanent discontinuation. Radiation pneumonitis during postoperative treatment has separate criteria: severe disease, or moderate disease that does not respond to standard treatment, also requires permanent discontinuation. Heart-function changes may require a pause or permanent stop, decided by the treating team.

Serious bleeding and infusion-site injury

Major bleeding can occur, including in patients taking anticoagulants or antiplatelet medicines and sometimes without obvious risk factors. Blood in vomit, black stools, uncontrolled bleeding or a severe new headache needs urgent care. Leaked infusion medicine can also injure tissue; delayed pain, redness, blistering or discolouration at the site should be reported promptly.

Severe infection or an allergic reaction

A serious infection can occur even without a high temperature, especially if steroids or fever-reducing medicines are being taken. New confusion, marked drowsiness, rapid breathing or collapse requires emergency care. Sudden throat swelling, severe wheezing or faintness can indicate a severe allergic reaction. These symptoms should not be managed by waiting at home for the next scheduled review.

Other medicines and vaccinations

Strong CYP3A4 inhibitors can increase exposure to the DM1 payload and should be avoided with Kadcyla when possible. These include certain antifungals, antibiotics and antivirals. The team should choose an alternative, arrange an appropriate treatment delay or provide closer monitoring if the combination cannot be avoided; do not change medicines yourself. Blood thinners and antiplatelet medicines require a coordinated bleeding-risk plan. Previous and concurrent heart-affecting treatments also matter. Do not substitute another trastuzumab-based medicine or use its dosing instructions.

Ask the oncology pharmacist to check new prescriptions, over-the-counter remedies and herbal or traditional products. Products described as natural are not necessarily safe with cancer treatment. Do not use an unproven supplement in place of an essential supportive medicine. Keep the team informed about medicines prescribed by other specialists so that advice is coordinated.

Discuss influenza, COVID-19 and other vaccines with the team. Non-live vaccines may be suitable, although the response can be reduced during treatment. Live vaccines require specific specialist advice. Timing after treatment depends on immune recovery and the complete regimen; there is no single waiting interval that is correct for every ADC-treated patient.

Everyday life

Eating does not determine absorption of this intravenous medicine. Aim for enough food and fluids, adjusting for nausea and following any kidney, heart or diabetes restrictions. Avoid a restrictive anticancer diet that causes weight loss. Discuss alcohol with the team, particularly if liver tests are abnormal or other medicines cause sedation.

Work may remain possible with flexible hours and time for appointments. Increase activity gradually and avoid tasks that become unsafe because of fatigue, poor balance or impaired vision. Do not drive if dizzy, sleepy, visually affected or unable to use the pedals safely. Sedating premedicines can also affect driving, so arrange transport for early appointments until you know the plan.

Protect numb feet and hands from burns or injury and use stable footwear. If platelets are low, ask about safe exercise and dental procedures. Check painkillers and alcohol with the team when liver tests are abnormal. Record any delayed infusion-site change so the unit can assess its progression.

Discuss travel before booking, especially long journeys or travel far from urgent care. Carry your treatment summary and enough supportive medicines. Use careful hand hygiene and food safety; avoid close contact with people who are clearly infectious. Complete social isolation is not automatically required. Ask about additional precautions when blood counts are very low.

Sex is often possible if comfortable, with the pregnancy precautions below and any advice about infection or bleeding. Ask the team whether barrier protection is needed after a dose to reduce exposure to drug residues in body fluids; the interval depends on the treatment. Caregivers cleaning urine, stool or vomit should follow the unit's handling advice, wear gloves when instructed and wash their hands afterwards. Keep medicines away from children and pets.

Fertility, pregnancy and breastfeeding

Use effective contraception during treatment and for at least seven months after the final dose if you could become pregnant. A treated man with a partner who could become pregnant should use effective contraception during treatment and for at least four months afterwards. Do not breastfeed during treatment or for at least seven months after the final dose.

Pregnancy should be discussed before treatment and reported promptly if it occurs or is suspected. Loss of periods does not reliably mean pregnancy is impossible. Vomiting or severe diarrhoea can interfere with oral contraception; seek advice about additional protection if this happens. Accompanying medicines may require longer precautions than the ADC itself, so obtain one clear end date for the complete regimen.

Fertility may be affected by treatment and previous therapies, and recovery cannot be guaranteed. Discuss sperm, egg or embryo preservation before starting when feasible. The interval for avoiding pregnancy is a safety precaution and does not itself establish whether fertility has recovered.

After treatment

Heart, liver, platelet or nerve abnormalities may need follow-up after the final infusion. Keep the treatment history available to new clinicians and report persistent or new symptoms. Completion of a fixed course does not mean that abnormal tests or ongoing symptoms can be left unchecked.

Keep attending the recommended blood tests, scans and clinical reviews. Retain a treatment summary with the exact ADC name, dates, significant reactions and any ongoing medication. Tell new clinicians about past treatment when an unexplained symptom is assessed. Continue contraception, breastfeeding restrictions and prescribed supportive medicines for their own specified periods, counted from the relevant final dose.

Recovery can be gradual and may involve physical rehabilitation, dietary support or help with anxiety and sleep. A follow-up visit is also an opportunity to discuss returning to work, travel and persistent symptoms. New severe symptoms still need urgent assessment between appointments; finishing treatment does not remove the need for the urgent-care plan.

Common questions