HER2 Targeted Therapy

HER2-positive cancer was once the most aggressive kind of breast cancer. Targeted drugs turned it into one of the most treatable.

The pathology report says HER2-positive, or HER2 3+, or HER2 amplified, and the oncologist has mentioned trastuzumab, pertuzumab or one of the newer drugs with long names. HER2, a protein on the surface of some cancer cells, drives them to divide. One breast cancer in five makes far too much of it, as do some cancers of the stomach and a few others. Before 2000 that made the cancer grow faster and come back sooner. Then came drugs that attach to HER2 and nothing else. In the HERA trial of 5,099 women, one year of trastuzumab after surgery lowered the risk of death by a quarter, and the benefit held at eleven years. In metastatic disease, two antibodies together with chemotherapy lifted median survival to 57.1 months in CLEOPATRA, and 37 percent of patients were alive at eight years. This page explains the test, the drugs, what they do for early and advanced cancer, what they ask of the heart and the lungs, and how treatment given every three weeks fits with a life lived partly in Istanbul and partly at home.

What HER2 is, and why it changes the treatment

HER2 Targeted Therapy means drugs aimed at a single protein, HER2, on the surface of cancer cells. Every cell carries a little of it. In HER2-positive cancer the gene that makes it has been copied many times over, the cell surface is crowded with the protein, and the signal it sends, divide and divide again, never switches off.

Before these drugs, HER2-positive breast cancer carried a worse outlook than most other types. It grew faster, spread earlier and came back sooner. The same protein that made it dangerous also made it a target, and targeted treatment has reversed the picture. A HER2-positive result today means the patient qualifies for some of the most effective drugs in oncology.

The result on the pathology report decides access to the treatment. A drug that transforms the outlook for a HER2-positive cancer does nothing for a HER2-negative one, and so the test comes first.

Where HER2 turns up

Breast cancer leads, with one case in five. Stomach cancer and cancer where the stomach meets the esophagus come next, with a similar share. Smaller numbers appear in cancers of the bowel, bile ducts, lung, bladder and uterus, and the test is increasingly run on all of them.

The test that decides

Two laboratory tests measure HER2 on tissue from the biopsy or the operation, and the pair of results decides which group a cancer belongs to.

IHC stains the protein and a pathologist scores it from 0 to 3+. FISH counts the copies of the gene. Results sit close to the line more frequently than families expect. Cancers change, too, so a metastasis is biopsied and retested when possible rather than assumed to match the original tumor. The review reads the report itself, how the test was done and when, and asks for the slides to be retested here when the result leaves doubt.

The drugs, in plain words

Almost every regimen pairs these drugs with something else, chemotherapy, hormone treatment, or each other. The stage chooses the combination.

Early breast cancer, before and after surgery

One year of trastuzumab after surgery is where the evidence starts. The HERA trial randomized 5,099 women with HER2-positive early breast cancer in 39 countries, after surgery and chemotherapy, to one year of trastuzumab, two years, or observation. Eleven years later, one year of trastuzumab had lowered the risk of the cancer returning by 24 percent and the risk of death by 26 percent. Ten-year disease-free survival was 69 percent against 63 percent, and half of the observation group had switched to trastuzumab once the early results were known, so the true benefit is larger than the figures show. Two years did no better than one.

Most HER2-positive tumors over 2 centimeters or with involved lymph nodes are now treated with chemotherapy and the two antibodies before surgery. The pathologist then looks at what is left. In a large share of patients nothing is, which carries an excellent outlook. When cancer remains, the next step changes.

Treatment in all runs for a year, counting from the first dose before surgery, with hormone tablets added for years afterwards when the cancer is also hormone receptor positive.

Metastatic breast cancer

Eight years of survival for more than a third of patients with metastatic disease. Unthinkable in 2000, and the reason these drugs are worth traveling for when they are not available at home.

When HER2-positive breast cancer has spread, targeted drugs are given in sequence, one line after another, each for as long as it works.

The sequence in practice runs pertuzumab and trastuzumab with a taxane first, then trastuzumab deruxtecan, then tucatinib with trastuzumab and capecitabine or trastuzumab emtansine, with hormone treatment woven in when the receptors allow. Brain metastases, common in this cancer, are treated with radiation or surgery alongside, and tucatinib and trastuzumab deruxtecan both reach them.

Stomach and other cancers

The heart

HER2 has a job in the heart muscle too, and blocking it can weaken the pumping. The effect stays silent in nearly every case, found on a scan rather than felt, and it reverses once the drug is paused in the great majority.

4.4 percent after one year of trastuzumab, 7.3 percent after two, 0.9 percent without it. The share of women in the HERA trial with a secondary heart event, mostly a fall in pumping strength seen on a scan, and nearly all of it during treatment.

How the heart is watched

An echocardiogram or a MUGA scan is done before the first dose and every three months while treatment continues. A drop in the pumping fraction below a set level pauses the drug, and heart tablets bring it back for nearly all, after which trastuzumab restarts. Anthracycline chemotherapy given in the same period adds to the strain, so many HER2 regimens now leave it out.

The lungs, with trastuzumab deruxtecan

An infusion day

From arrival to home

Blood tests come first in the morning, with the heart scan when it is due, then a short visit with the oncologist, who checks the results and asks about side effects. The drug follows. Trastuzumab and pertuzumab under the skin take five to eight minutes. Into a vein, the first dose runs over ninety minutes and later doses over thirty to sixty, and trastuzumab deruxtecan runs over ninety minutes the first time and thirty after. Observation lasts thirty minutes to six hours after the first dose, for a reaction, and less after later ones. Home the same day.

Days in Istanbul

The first cycle here, the rest near home. A treatment given every three weeks for a year cannot sensibly be given by air, and the injection under the skin takes five minutes in any clinic.

The coordinator plans the length of stay around the cycle dates. No dose waits for a flight.

What a quote contains

No figure appears here. HER2 drugs rank among the more expensive in oncology, and the total depends on which drug, for how long, and how much is given here.

The lines of a quote

A quote you can compare names the drug, the form, the number of cycles, and whether the heart scans are inside the figure. Ask for biosimilar trastuzumab by name. It follows the free review.

Coordinator, language, companion

Language

Biruni Hospital gives every international patient one coordinator from the first message, reachable on the same WhatsApp number afterwards. The international patients team works in English, Arabic, French, Russian, Serbian, Romanian and Spanish with interpreters for other languages, and for targeted therapy the interpreter matters most at the first consultation, where the drug, the schedule and the warning signs for the heart and the lungs are explained.

Continuing at home

Once you get back home, your oncologist receives the protocol, with the drug, dose and schedule for every cycle, the baseline heart scan, the pathology and a calendar for scans.

Same day, local doctor. A new cough or breathlessness on deruxtecan, swollen ankles or breathlessness lying flat on trastuzumab, or a fever with low blood counts.

Every result goes to the coordinator. The oncologist here reviews it at no charge and says whether to continue, pause or change, and when a change is needed, the new protocol reaches your oncologist at home in writing within days, with the reasons, the new drug, its dose and its schedule, so that treatment does not stall while the two teams talk.

HER2 Targeted Therapy FAQ