Herceptin is the brand name of the targeted cancer drug trastuzumab.

It’s a biologic drug used to treat cancers that have large amounts of the protein HER2 (human epidermal growth factor receptor 2). These HER2-positive cancers include:

  • early breast cancer
  • metastatic (or stage 4) breast cancer
  • metastatic (or stage 4) gastric cancer

The HER2 protein in some breast and gastric cancers makes the cancer cells grow and divide. Herceptin attaches to the HER2 receptors on the surface of the cancer cells, which blocks the cells from receiving growth signals. As a result, growth is slowed or stopped.

Herceptin is administered intravenously (through a vein into the bloodstream). It takes around 90 minutes to administer the first dose of Herceptin and around 30 to 90 minutes for all other doses.

For early breast cancer

If you have an earlier stage of breast cancer, your treatment may be Herceptin alone or Herceptin combined with chemotherapy. Herceptin can be administered before or after chemotherapy. It can also be administered before or after surgery.

Treatment often lasts 6 months to 1 year.

When it’s used as the sole treatment for early breast cancer, Herceptin is administered every 3 weeks. When it’s used alongside chemotherapy, the drug is administered weekly for the first 12 or 18 weeks. Afterward, it’s administered every 3 weeks.

For metastatic breast cancer

If you’ve never received treatment for metastatic breast cancer before, your initial treatment will be Herceptin combined with the chemotherapy drug paclitaxel. If you’ve had at least one course of chemotherapy, Herceptin will be used on its own.

Treatment is administered weekly and lasts until disease progression.

For metastatic gastric cancer

For gastroesophageal cancer, such as adenocarcinoma, Herceptin is typically prescribed if you haven’t received any prior treatment for metastatic gastric cancer.

It’s administered along with either a combination of cisplatin and capecitabine (Xeloda) or a combination of cisplatin and fluorouracil. Cisplatin, capecitabine, and fluorouracil are all chemotherapy drugs.

For advanced cancer affecting the stomach or esophagus, Herceptin will typically be administered every 3 weeks and lasts until disease progression.

Herceptin side effects will vary slightly, depending on which type of cancer it’s being used to treat.

Common side effects

More than 1 in 10 people with metastatic gastric or metastatic breast cancer may experience fever.

The other side effects seen in more than 10 percent of people with metastatic gastric cancer are:

The other side effects seen in more than 10 percent of people with metastatic breast cancer are:

The side effects seen in more than 5 percent of people with early breast cancer are:

Symptoms such as fever, chills, and nausea are typically associated with an infusion reaction.

People who experience side effects of Herceptin often find that the side effects become less severe after their initial treatment.

Long-term side effects

In some cases, Herceptin can cause serious, long-term side effects and complications.

Effects during and after pregnancy

People who can become pregnant are advised to use contraception during their treatment period and for 7 months after their treatment ends.

Herceptin may cause oligohydramnios, or low levels of amniotic fluid. Oligohydramnios can also lead to serious complications affecting the baby, including underdeveloped lungs and neonatal death.

Effects on the heart

People who take Herceptin for breast cancer are at a higher risk for long-term heart damage, according to research. This risk is even greater when Herceptin is taken with anthracyclines, a group of chemotherapy drugs known to cause heart damage. Doxorubicin (Doxil) is an example of an anthracycline.

According to a 2019 study, you can reduce your risk for heart problems by adding an angiotensin-converting enzyme (ACE) inhibitor or a beta-blocker to a treatment regimen that contains Herceptin and an anthracycline.

People who had the ACE inhibitor lisinopril (Prinivil, Zestril) or the beta-blocker carvedilol (Coreg) added to their treatment regimen were less likely to experience heart damage than people who had a placebo added.

Before starting Herceptin therapy, talk with your doctor about a multiple-gated acquisition (MUGA) scan or an echocardiogram. These exams can be used to determine how well your heart functions.

During your year of treatment, your doctor will test your heart every 3 months. After your treatment ends, your doctor will test your heart every 6 months for at least 2 years.

Seek emergency medical help if you’re taking Herceptin and you develop any symptoms of heart failure. They include:

Rare side effects

On rare occasions, a person could have a serious reaction to Herceptin that interferes with their breathing.

Other rare side effects that may occur include:

Before starting Herceptin therapy, talk with your doctor about a full examination to identify any possible lung problems.

If one of these reactions should occur, it will most likely happen during the infusion or within the first 24 hours of the first dose. If you’re currently receiving treatment with Herceptin and have been tolerating it well, it’s unlikely you’ll experience these serious reactions.

Other side effects seen in fewer than 1 percent of people taking the medication for early breast cancer include:

If Herceptin is being administered along with chemotherapy, you may also experience some side effects of chemotherapy, such as:

The FDA approved Herceptin Hylecta, a combination of trastuzumab and hyaluronidase-oysk, in 2019. It can be used to treat early or metastatic breast cancer, but not metastatic gastric cancer.

Unlike Herceptin, Herceptin Hylecta is a subcutaneous injectable medication. As a result, it can be administered more quickly. It takes 2 to 5 minutes to administer one dose of Herceptin Hylecta. IV treatment with traditional Herceptin often lasts 30 to 90 minutes.

Herceptin Hylecta is taken every 3 weeks for up to 1 year.

Common or long-term side effects are similar to the common or long-term side effects of Herceptin. The side effects that are seen in more than 10 percent of people with early or metastatic breast cancer are:

  • fever
  • headache
  • cough
  • rash

Side effects that are seen in more than 10 percent of people with early breast cancer are:

  • fatigue
  • diarrhea
  • nausea
  • injection site reactions
  • upper respiratory tract infections
  • swelling
  • flushing
  • myalgia, or muscle aches
  • arthralgia, which is joint pain without inflammation
  • pain in the extremities

Side effects that are seen in more than 10 percent of people with metastatic breast cancer are:

  • chills
  • infection
  • congestive heart failure
  • insomnia

Cardiac monitoring is also required.

Biosimilars, which are reverse-engineered to produce similar results as biologics, are available under the following names:

  • trastuzumab-anns (Kanjinti)
  • trastuzumab-dkst (Ogivri)
  • trastuzumab-dttb (Ontruzant)
  • trastuzumab-pkrb (Herzuma)
  • trastuzumab-qyyp (Trazimera)

The biosimilars all have the same common side effects as Herceptin. One benefit of biosimilars is that they’re typically cheaper than the biologic they’re based on.

When your doctor talks to you about Herceptin, ask them about your risk for heart and lung problems. Although these side effects are relatively rare, being prepared is always a wise decision.

Your doctor might recommend a MUGA scan or an echocardiogram before you begin Herceptin therapy. Expect to be monitored for serious side effects during treatment as well.

It’s more likely that you’ll experience flu-like symptoms than serious side effects. These symptoms usually subside after your first treatment.