HER2+ breast cancer: 20 years since trastuzumab changed everything

Twenty years ago today, an antibiotic-sized vial changed what it meant to be diagnosed with HER2-positive breast cancer in Australia.

On 1 October 2006, trastuzumab — the targeted therapy developed after the discovery that some breast cancers carry an excess of the HER2 protein that drives their growth — was listed on Australia’s Pharmaceutical Benefits Scheme for early-stage HER2-positive disease. Before that listing, women were paying $50,000 to $70,000 a year out-of-pocket for access. Some sold homes and farms. Many simply could not access it at all.

Today that history is worth understanding — not only as a story about one drug, but as a map of how targeted therapy works, what it means for women receiving a HER2-positive diagnosis in 2026, and what the journey from bench to PBS looks like.

What HER2-positive means — and why it matters

HER2 stands for human epidermal growth factor receptor 2. It is a protein that, when overexpressed on the surface of breast cancer cells, functions as a growth accelerator — driving aggressive cell proliferation. HER2-positive breast cancer accounts for up to one in five breast cancer diagnoses, making it one of the most common subtypes.

Before trastuzumab, HER2-positive breast cancer carried a particularly poor prognosis precisely because of that aggressive biology. The drug’s mechanism — it binds to the HER2 receptor and blocks the growth signal — represented the first demonstration that a targeted therapy could alter the trajectory of this subtype at the early-stage, curative-intent level.

HER2 status is tested automatically as part of standard breast cancer pathology in Australia. Women do not need to request it separately. The result comes back alongside oestrogen and progesterone receptor status as part of the full tumour biology picture that shapes treatment planning.

The HERA trial and what it showed

The global HERA trial enrolled more than 5,000 patients across 39 countries and demonstrated that one year of trastuzumab significantly improves long-term disease-free survival in people with HER2-positive early breast cancer treated with chemotherapy. It was the trial that converted the PBS access question from theoretical to urgent.

Donna Rullo, the HERA trial’s first Australian patient, has described what the trial meant: she survived to see her son grow up, marry, and have children. Before that trial — and without the PBS listing that followed — the women in her situation were measuring time in years, not decades.

The five-year survival rate for breast cancer overall has moved from 75% in 1987–1991 to 93% in 2017–2021. Trastuzumab and the targeted therapy generation it opened are a significant part of that shift for HER2-positive disease specifically.

What the treatment landscape looks like in 2026

Trastuzumab is no longer the only HER2-directed therapy in the Australian treatment toolkit. The twenty years since the initial PBS listing have produced a second and third generation of agents.

Pertuzumab, used alongside trastuzumab and chemotherapy in the neoadjuvant setting for high-risk early disease, is now PBS-listed. T-DM1 (trastuzumab emtansine) — essentially trastuzumab carrying a chemotherapy payload directly to HER2-expressing cells — is available for residual disease after neoadjuvant treatment. Tucatinib and trastuzumab deruxtecan represent more recent additions to the metastatic HER2-positive landscape, with trastuzumab deruxtecan showing activity even in HER2-low disease that does not reach the HER2-positive threshold.

The treatment decision tree for HER2-positive breast cancer has grown significantly more complex — and more nuanced — than the single-drug picture of 2006. Oncologists now discuss which combination of targeted agents is most appropriate based on staging, receptor co-expression, response to neoadjuvant therapy, and where in the treatment pathway the conversation is happening.

Both-and: access and the PBS pathway

The trastuzumab story is also a story about the Pharmaceutical Benefits Scheme doing exactly what it is designed to do. A drug with compelling efficacy data that was accessible only to women with the means to pay tens of thousands of dollars annually became accessible to every Australian woman with a HER2-positive diagnosis within two years of the PBS submission being processed.

The counter-weight is in the PBS timeline itself. Women in the years between the HERA trial results and the PBS listing were navigating access on personal resources, charity programs, and early compassionate access schemes. The PBS process works — and it is not instant, and the gap years carry a real human cost.

That tension sits within every new targeted therapy listing discussion, including the newer agents whose PBS submissions are in various stages of review today. The principle is sound. The lag between evidence and equitable access is where the advocacy work still lives.

2 cents

If you or someone close to you has been diagnosed with breast cancer recently, HER2 status will be part of the pathology results — ask your oncologist specifically what it means for the treatment pathway. A HER2-positive result is not a worse hand than it once was. It is a result with a specific targeted treatment attached to it.

The 20th anniversary today is a useful moment to understand that treatment landscapes are not static — and that the version of this disease being treated in 2026 is genuinely different from 2006.

Verdict: yes — worth knowing about.

---

Sources cited

1. How a breast cancer trial changed survivors’ lives — ABC Health, 1 October 2026