AuthorisedTherapeutic exploratory (Phase II)Interventional

OASIS-ImmunoPET_Antibody-based PET imaging and treatment response in breast cancer treated with an antibody-drug conjugate according to current standard indications.

This phase II clinical trial is exploring a new imaging technique for people with breast cancer who are receiving a standard targeted treatment called T-DXd. Standard scans, like CT or MRI, measure tumour size, but they do not always show quickly if cancer cells are becoming inactive. In this study, doctors are testing an 'ImmunoPET' scan using a gentle radioactive tracer called 89Zr-trastuzumab. This tracer attaches directly to breast cancer cells, lighting them up on a PET scanner. Researchers want to see if these scans can show how the cancer is responding after just three cycles of treatment and at six months. They are also checking whether this scan can detect if cancer has spread to the brain earlier than standard hospital scans. The hope is that this will help doctors tailor treatments more quickly and accurately in the future.

At a glance

Status

Authorised

Phase

Therapeutic exploratory (Phase II)

Sponsor

Unicancer

Enrolment target

Start

23 Sep 2026

What is this study about?

When treating breast cancer, doctors often use targeted medicines known as antibody-drug conjugates (such as T-DXd). These medicines seek out specific proteins on cancer cells to deliver treatment directly to them. To see how well the medicine is working, patients normally have regular CT or MRI scans. However, these regular scans mostly look at the size of tumours, which can take time to change even after the cancer cells have stopped growing.

This trial introduces a specialised scan called an ImmunoPET scan. It combines an antibody that recognises breast cancer cells with a tiny, safe amount of a radioactive marker (called 89Zr-trastuzumab). When injected into the bloodstream, this marker travels to the cancer cells and 'highlights' them on a PET scanner. This allows doctors to see the active biology of the tumour, rather than just its outline.

The main goal of the trial is to see if the ImmunoPET scan can accurately measure how the tumour's activity changes after three cycles of standard treatment and at six months. The researchers also want to find out if this scan is better or quicker at spotting whether cancer has spread to other areas, such as the brain, compared with routine scans like CT or MRI.

By taking part, patients help doctors understand whether this advanced scanning technique can guide future cancer care. If successful, it could help doctors know much earlier whether a treatment is working, saving valuable time and helping tailor care to each person's needs.

Key takeaways

Tests a new ImmunoPET scan using 89Zr-trastuzumab in people with breast cancer.
Aims to show how well targeted treatment (T-DXd) is working after 3 cycles and at 6 months.
Checks if the new scan can spot cancer spread, including to the brain, earlier than usual scans.
Participants receive standard cancer treatment alongside the extra trial scans.
Open to adults aged 18 and over who are eligible for T-DXd therapy.

Who may be eligible?

This trial is open to adults aged 18 and over who have breast cancer and are due to receive standard treatment with a targeted medicine called T-DXd (trastuzumab deruxtecan). Both women and men can join.

Because this study focuses on how a specific treatment works, participants must be planning to have this standard drug as part of their routine care. You will need to be well enough to attend hospital visits and lie relatively flat for scanning procedures.

You may not be able to take part if you are unable to have PET scans, have had severe allergic reactions to antibody treatments in the past, or are pregnant or breastfeeding. Your cancer doctor will check your overall health and medical history to make sure the study is safe and suitable for you.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am aged 18 or older.
I have been diagnosed with breast cancer.
My doctor has recommended standard treatment with T-DXd (trastuzumab deruxtecan).
I am able to attend extra hospital visits for specialised scans.
I can lie reasonably flat and still inside a PET scanner.

Answer every question to see your result.

What does participation involve?

If you take part, you will receive your standard cancer treatment (T-DXd) as planned by your healthcare team. In addition to your regular care, you will have special ImmunoPET scans. Before each study scan, you will receive a small injection of the study tracer (89Zr-trastuzumab) through a vein, usually followed by a scan a few days later to allow the tracer to settle in the body. Scans are generally planned before you start treatment, after three treatment cycles, and around six months later. You will also continue with your routine hospital check-ups and standard scans (such as CT or MRI). The study team will track your health throughout your treatment course and monitor any changes in your condition.

Potential risks and benefits

Taking part may not directly improve your own health, as the main treatment is already standard care. However, you will be closely monitored, and the results could help improve how breast cancer is scanned and treated for others in the future. The risks include mild side effects from the tracer injection, such as temporary bruising, redness at the needle site, or rare allergic reactions. The PET scan involves a small amount of radiation, which is kept within safe medical limits. Some people may also feel slightly claustrophobic inside the scanner. Your participation is completely voluntary, and you can withdraw at any time without your regular NHS care being affected.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Belgium

Common questions

What is an ImmunoPET scan?

It is an advanced PET scan that uses an antibody combined with a mild radioactive tracer to find and highlight specific cancer cells in the body.

Does this trial replace my normal cancer treatment?

No. You will still receive the standard targeted cancer medicine recommended by your doctor. The trial is simply testing a new way of scanning your body while you have this treatment.

Is the radioactive tracer safe?

Yes. The amount of radiation used in medical tracers is small and carefully regulated to ensure it is safe. The body naturally clears the tracer over time.

Will taking part require extra hospital visits?

Yes, you will need extra appointments for the tracer injections and the special PET scans, in addition to your routine treatment appointments.

Can I leave the study if I change my mind?

Yes, you can leave the study at any time. You do not need to give a reason, and your regular NHS treatment and support will continue as normal.