Trastuzumab emtansine
Say it: tras-TOO-zoo-mab em-TAN-seen · Brand names: Kadcyla
Trastuzumab emtansine is a targeted medicine that delivers a cancer drug straight to breast cancer cells that have a protein called HER2.
What it is
It is made of two parts joined together: an antibody that finds a protein called HER2 on cancer cells, and a strong cancer medicine. The antibody carries the medicine straight to the cancer cell, so more of it reaches the cancer and less reaches healthy cells. The antibody part also blocks HER2 signals that help the cancer grow.
Often used for
- HER2 positive breast cancer that has spread
- HER2 positive early breast cancer when some cancer is left after treatment before surgery
How you get it
You get it as an infusion into a vein at a clinic. The first infusion takes about 90 minutes, and later ones take about 30 minutes if you do well. Most people get it once every 3 weeks. Your schedule may be different.
Common side effects and what helps
- Feeling tired. Rest and short walks can help.
- Nausea. Eat small, bland meals and take anti-nausea medicine if your team gives it to you.
- Muscle or joint pain. Ask your team what pain medicine is safe.
- Low platelets, which can make you bruise or bleed more easily. Use a soft toothbrush and an electric razor.
- Nosebleeds. Pinch your nose and lean forward. Tell your team if they happen often.
- Headache. Rest and drink fluids.
- Constipation. Drink fluids and ask your team about a stool softener.
- Numbness or tingling in your hands or feet. Tell your team if it gets worse.
Call your care team right away if you have
- Bleeding that will not stop, vomiting blood, black stools, or a very bad headache
- Yellow skin or eyes, dark urine, or pain on the right side of your belly
- Swelling in your legs, a racing heartbeat, or shortness of breath
- New cough or trouble breathing
- A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher
- Trouble breathing, chills, flushing, or rash during or after the infusion
Before you start, tell your team
- If you have liver problems
- If you have heart problems
- If you take blood thinners
- If you are pregnant, may become pregnant, or are breastfeeding
- All the medicines, vitamins, and herbal products you take
Good to know
- This medicine can harm the liver. You will have blood tests to check your liver before each dose.
- This medicine can weaken the heart. You will have heart tests before and during treatment.
- You will have blood tests to check your platelets.
- This medicine can harm an unborn baby. Ask your team about birth control during treatment and for months after it ends.
Questions to ask
- How often will you check my heart and liver?
- What should I do if I have a nosebleed or bruise easily?
- How many treatments will I get?
- Is it safe to take pain relievers like ibuprofen?
Side effect guides
- Fatigue (tiredness)
- Nausea and vomiting
- Constipation
- Low platelets and bleeding
- Neuropathy (numbness and tingling)
- Pain
Sources
Quick answers
- What is Trastuzumab emtansine?
- Trastuzumab emtansine is a targeted medicine that delivers a cancer drug straight to breast cancer cells that have a protein called HER2. Brand names: Kadcyla.
- What is Trastuzumab emtansine used for?
- HER2 positive breast cancer that has spread; HER2 positive early breast cancer when some cancer is left after treatment before surgery.
- How is Trastuzumab emtansine given?
- You get it as an infusion into a vein at a clinic. The first infusion takes about 90 minutes, and later ones take about 30 minutes if you do well. Most people get it once every 3 weeks. Your schedule may be different.
- What are the common side effects of Trastuzumab emtansine?
- Feeling tired. Nausea. Muscle or joint pain. Low platelets, which can make you bruise or bleed more easily. Nosebleeds. Headache. Constipation. Numbness or tingling in your hands or feet.
- When should I call my care team while taking Trastuzumab emtansine?
- Bleeding that will not stop, vomiting blood, black stools, or a very bad headache; Yellow skin or eyes, dark urine, or pain on the right side of your belly; Swelling in your legs, a racing heartbeat, or shortness of breath; New cough or trouble breathing; A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher; Trouble breathing, chills, flushing, or rash during or after the infusion.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.