Medical Oncologist
Medicines
Trastuzumab emtansine (Kadcyla) for breast cancer: the complete patient guide
Trastuzumab emtansine is a HER2 antibody joined to a chemotherapy medicine, used for HER2-positive breast cancer. It is given every three weeks as a drip, usually for fourteen cycles after surgery when cancer remains, or for as long as it works in advanced cancer. This guide covers how it works, treatment days, side effects, monitoring and questions to ask.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
On this page
- What is trastuzumab emtansine, and what does treatment involve?
- Four things to know before you start
- Trastuzumab emtansine in brief
- The vocabulary, in plain language
- Honest realities about T-DM1
- T-DM1 after surgery
- T-DM1 when cancer has spread
- Questions worth asking your team
- What people assume about trastuzumab emtansine
- Common questions about trastuzumab emtansine
The short answer
What is trastuzumab emtansine, and what does treatment involve?
Trastuzumab emtansine is a medicine for HER2-positive breast cancer. You may hear it called T-DM1, or by its brand name, Kadcyla. It is an antibody-drug conjugate, which means it joins trastuzumab, an antibody that attaches to the HER2 protein, to a chemotherapy medicine called DM1. The antibody carries the chemotherapy mainly to cancer cells that have a lot of HER2, where it is released inside the cell. T-DM1 is used in two main situations. In early breast cancer, it is given after surgery when some invasive cancer was still found despite chemotherapy and HER2 treatment before the operation. Here it replaces trastuzumab and is usually given for fourteen cycles. In advanced breast cancer, it is one of several HER2 treatments and is usually continued for as long as it keeps the cancer controlled. It is given as a drip in a day-care unit once every three weeks, with the dose based on your weight. Common side effects include tiredness, nausea, headache, nosebleeds, low platelets and raised liver enzymes. Some people get tingling in the hands and feet. Heavy hair loss is uncommon. Blood tests are checked before every dose and heart scans every few months. T-DM1 can harm an unborn baby, so reliable contraception is needed during treatment and for seven months afterwards. This guide brings together the key things to know and links to more detailed pages.
A HER2 antibody carrying chemotherapy
It delivers chemotherapy mainly to HER2-rich cancer cells, though some reaches healthy tissue.
Two main uses
After surgery when cancer remains, and in advanced HER2-positive breast cancer.
Regular checks keep it safe
Blood tests before each dose and repeated heart scans catch problems early.
This page gives general information only. Your own oncology team decides whether T-DM1 is right for you and how it is given.The essentials
Four things to know before you start
A quick overview of how treatment fits into your life.
How it is given
A drip into a vein every three weeks. The first runs slowly with a longer wait afterwards; later ones are usually quicker.
How long it lasts
Usually fourteen cycles after surgery. In advanced cancer, it continues while it is working and side effects are manageable.
Delays for blood test results are common and routine.What is checked
Platelets and liver tests before each dose, weight for the dose calculation, and heart pumping strength every few months.
What to report quickly
Some symptoms need prompt advice rather than waiting for your next visit.
Call your team for
- Fever, bleeding that will not stop or black stools
- Yellow skin or eyes, or dark urine
- Breathlessness, a new cough or ankle swelling
At a glance
Trastuzumab emtansine in brief
Question
General answer
What type of cancer is it for?
HER2-positive breast cancer only
Is it given with other HER2 medicines?
Not usually; it already contains a HER2 antibody
Can hormone tablets be taken with it?
Yes, often, if the cancer is also hormone receptor-positive
Does it cause hair loss?
Heavy hair loss is uncommon, though some thinning can occur
Is it safe in pregnancy?
No; contraception is needed during treatment and for seven months after
Words you will hear
The vocabulary, in plain language
- T-DM1
- A short name for trastuzumab emtansine. Kadcyla is its brand name.
- HER2-positive
- A breast cancer whose cells make too much of the HER2 growth protein.
- Residual disease
- Invasive cancer still present at surgery after treatment given before the operation.
- Cycle
- One dose followed by a three-week gap.
- Platelets
- Blood cells that help clotting, often lowered for a time by T-DM1.
- Ejection fraction
- A heart scan measure of pumping strength, checked during HER2 treatment.
Being straight with you
Honest realities about T-DM1
T-DM1 is an important and well-studied medicine. It helps to hold realistic expectations about what it can and cannot do.
It lowers risk but cannot remove it
After surgery, it reduces the chance of cancer returning. Some people still have a recurrence despite completing treatment.
It is gentler for many, not for all
Some people sail through; others find tiredness, nerve changes or repeated delays difficult.
It is expensive
Cost and insurance coverage are real concerns in India, and it is reasonable to discuss them with your team early.
What this page cannot tell you
It cannot tell you whether T-DM1 is the right choice for you, or how well it will work in your case. Your oncologist can explain your situation.
Talk to our team
Have a question about your situation?
Call the helpline or leave your details, and someone will help you arrange a consultation at the CION centre nearest you. One helpline serves every CION centre.
Call 1800 202 8726
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Early breast cancer
T-DM1 after surgery
If chemotherapy and HER2 treatment before surgery do not fully clear the invasive cancer, the risk of recurrence is higher. T-DM1 is offered to lower that risk.
The evidence
A large international study found that switching to T-DM1 lowered the chance of the cancer coming back compared with continuing trastuzumab, and longer follow-up suggested improved survival.
Other treatment at the same time
Radiotherapy, if needed, is often given during T-DM1. Hormone tablets usually start alongside it for hormone receptor-positive cancer.
If side effects are too much
Your team may lower the dose, or switch to trastuzumab to complete a year of HER2 treatment.
Advanced breast cancer
T-DM1 when cancer has spread
For advanced HER2-positive breast cancer, T-DM1 is one of several HER2 treatments used in sequence. It was shown to control the cancer for longer in people who had already had trastuzumab and taxane chemotherapy.
Where it fits now
Where trastuzumab deruxtecan is available, it is often used earlier, and T-DM1 may follow later. Choices depend on earlier treatment, side effects and access.
Checking progress
Scans every few months, along with how you feel, show whether T-DM1 is keeping the cancer controlled.
Quality of life
Your comfort and priorities matter. Tell your team how treatment is affecting daily life so they can adjust the plan.
Before you start
Questions worth asking your team
Writing these questions down before your first visit helps you get the most from the conversation.
About the plan
Why is T-DM1 recommended for me, how many cycles are planned, and what happens if I cannot finish them?
About safety
Which symptoms should I report straight away, and which number should I call out of hours?
About everyday life
Can I work, travel and exercise during treatment, and are there medicines or remedies I should avoid?
Commonly believed
What people assume about trastuzumab emtansine
T-DM1 is just another name for trastuzumab.
It is trastuzumab joined to a chemotherapy medicine, so it is a different treatment.
Being targeted means it has no real side effects.
Low platelets, liver changes, tiredness and nerve changes are common and need monitoring.
Everyone on it loses their hair.
Heavy hair loss is uncommon with T-DM1.
A delayed dose means the treatment has failed.
Delays for blood test results are routine safety steps and treatment usually continues.
Questions we are asked
Common questions about trastuzumab emtansine
Is Kadcyla the same as trastuzumab emtansine?
Yes. Kadcyla is the brand name, trastuzumab emtansine is the medicine's name, and T-DM1 is a common short name. Other approved versions may also be available. Always check that the full name on the pack matches your prescription, because trastuzumab alone is a different medicine.
How long does each infusion take?
The first drip usually runs over about an hour and a half, followed by a period of observation. If that goes well, later drips often run over about half an hour, with a shorter wait. Blood tests and pharmacy preparation add to the total time you spend in the unit.
What are the most common side effects?
Tiredness, nausea, headache, constipation, muscle and joint aches and nosebleeds are common. On blood tests, low platelets and raised liver enzymes are frequent and often cause no symptoms. Some people develop tingling or numbness in the hands and feet over several cycles.
Why are blood tests done before every dose?
T-DM1 can lower platelets and raise liver enzymes. Checking before each dose allows your team to delay or lower the dose if needed, which keeps treatment safe. Most changes are mild and settle, so treatment usually continues.
Can I have T-DM1 if I have heart problems?
It depends on how well your heart pumps. A heart scan is done before starting and every few months during treatment. If pumping strength is low or falls, your team may pause treatment and involve a heart specialist before deciding how to continue.
Do I need to avoid pregnancy?
Yes. T-DM1 can harm an unborn baby. Reliable contraception is needed during treatment and for seven months after the last dose, and partners of men on treatment should also avoid pregnancy. Non-hormonal methods are usually advised if the cancer is hormone receptor-positive.
Are there medicines I should avoid?
Some antifungals, the antibiotic clarithromycin and certain HIV medicines can raise levels of the chemotherapy part. Blood thinners and anti-inflammatory painkillers add to bleeding risk. Check with your team or pharmacist before starting any new medicine, supplement or herbal remedy.
What happens after the last cycle?
After surgery, you move to regular follow-up, often continuing hormone tablets if your cancer is hormone receptor-positive. Side effects usually ease over weeks to months, though nerve changes may take longer. Keep using contraception for seven months and report any new symptoms.
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Sources
- Cancer Research UK — Trastuzumab emtansine (Kadcyla)
- National Cancer Institute — Ado-trastuzumab emtansine
- European Medicines Agency — Kadcyla: product information
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.