Pertuzumab myths: 'it is just a second Herceptin'

No. Pertuzumab, sold as Perjeta, and trastuzumab, often known by the brand name Herceptin, are both antibodies that attach to HER2, the growth protein found in large amounts on HER2-positive breast cancer cells. But they attach to different parts of that protein and work in complementary ways. HER2 sends growth signals most strongly when it pairs up with partner proteins, especially one called HER3. Pertuzumab sits on the part of HER2 that it uses to pair up, so it blocks those partnerships. Trastuzumab sits on a different part and mainly disrupts signalling from HER2 on its own, while also flagging the cell to the immune system. Using both together is called dual HER2 blockade, and research shows the combination does more than trastuzumab alone in some situations. That is why pertuzumab is always given with trastuzumab, not instead of it. Other common beliefs also deserve a closer look. Pertuzumab is not chemotherapy, and it does not cause hair loss, although the chemotherapy often given with it does. It is not needed by everyone with HER2-positive cancer, since its benefit depends on stage and risk. It does add some side effects, mainly diarrhoea, but heart problems do not appear to be much more common than with trastuzumab alone. Clearing up these myths helps you understand why it is being offered.

A different target on the same protein

Pertuzumab blocks HER2 from pairing with partner proteins; trastuzumab acts on another part.

Designed to work together

Pertuzumab is given alongside trastuzumab, not as a replacement for it.

Not a chemotherapy

It is a targeted antibody. Hair loss during treatment comes from chemotherapy given with it.

Correcting myths should not swing too far the other way. Pertuzumab is valuable, but it has limits worth knowing.

The benefit varies a lot

As a first treatment for advanced cancer it helped people live longer. After surgery in early cancer, the added benefit was modest and mostly in higher-risk cancers.

It does add side effects

Diarrhoea is the main extra side effect, especially during chemotherapy, and rash or tiredness can also increase.

It adds cost

For many families in India, the extra expense is significant and fair to discuss.

What this page cannot tell you

It cannot tell you whether pertuzumab will help your cancer. Your oncologist can explain your likely benefit.

This is one of the most common worries. Trastuzumab can weaken heart pumping strength in some people, so it is natural to fear that two HER2 antibodies mean twice the risk.

What studies found

Large studies did not show a major increase in heart problems when pertuzumab was added to trastuzumab. Most heart changes were mild and improved when treatment was paused.

Why scans continue

Heart scans are still done before and during treatment, because a small number of people do develop reduced pumping strength.

Symptoms to report

Tell your team about breathlessness, ankle swelling, a racing heartbeat or needing more pillows to sleep.