‘Unprecedented’ breast cancer trial results explained

As you’ll probably have seen from this morning’s headlines, UK researchers running a clinical trial have presented some exciting preliminary results at a the tenth European Breast Cancer Conference.

The trial looked at the effects of combining two drugs – trastuzumab (Herceptin) and lapatinib –before surgery, in women with HER2 positive breast cancer.

Called EPHOS B, the trial was led by UK researchers in London and Manchester, and funded by CRUK.

So what did these early results show, and why the excitement?

The pre-trial setting

When a woman is diagnosed with breast cancer, it is generally classified as one of a number of subtypes. One of these is called ‘HER2 positive’ breast cancer, because the cancer cells have large amounts of a molecule called HER2 on their surface.

This means they’re more likely to respond to drugs designed to target this molecule – including both trastuzumab and lapatinib. (You can read more about HER2 positive breast cancer in this blog post.)

The treatment these women are offered depends on a number of things, such as the stage of their breast cancer, whether they are pre- or post-menopausal and their all-round general health.

Some HER2 positive patients have chemotherapy with or without trastuzumab (Herceptin) right away, to try and shrink their tumour before surgery. Then after surgery, these women may have more chemotherapy and maybe Herceptin to help stop the cancer coming back.

Other women are scheduled to have surgery first, and are then given an extensive course of chemotherapy combined with Herceptin. Again, this is to help stop the cancer returning.

It’s this second group that the EPHOS B trial looked at.

The trial

EPHOS B included 257 women who had been diagnosed with HER2 positive breast cancer and were waiting to have surgery.

It was run in two parts. In the first, 130 women were assigned to one of three groups – some received Herceptin (trastuzumab), others received lapatinib. Both these groups were treated for 11 days after diagnosis and before surgery. A third group received no drug treatment before surgery (the control group).

But, as often happens in science, other evidence became available during the trial which showed that giving both drugs together was better than either alone.

So the researchers changed tack. The next 127 women recruited to the trial were assigned to either a control group, a Herceptin only group, or group given a combination of Herceptin and lapatinib.

Following their initial treatment, all women involved in the trial went on to have standard care, including surgery.

The results

After surgery, the researchers analysed the resulting tissue to see if there was a difference between the various groups. They measured a variety of things in each sample, including hallmarks of cell death and cell growth, and the size of any remaining tumour tissue.

Excitingly, in tissue from seven of the 66 women who had the combination treatment they saw what, in medical terms, is known as a ‘pathological complete response’.

In non-medical terms, their tumours had gone.

And for another 11 women the drug combination shrank their tumour considerably – these women are described as having minimal residual disease – in other words, there were only microscopic traces of the disease left over after treatment.

It’s important to remember that while this generally suggests a treatment has worked well, it also means there are still cancer cells remaining from which the disease could grow back.

This is especially important because HER2 positive breast cancer is more likely to come back after treatment than some other types of breast cancer.

But nevertheless, these are exciting results, particularly when you consider that women with Stage 2 cancer – where the cancer had spread to the lymph nodes – were among those who responded to the combination therapy.

They’re also exciting when compared to the other groups in the trial. No women given trastuzumab only, or no drug treatment, had a complete response, while only one woman in the trastuzumab-only group had minimal residual disease.

It’s also important to remember that the researchers didn’t see any response in the other 48 women who received the drug combination. Clearly, there’s something different about some HER2 positive tumours that makes them exquisitely sensitive to the drug combination.

The next steps

These results indicate that there’s a group of HER2 positive breast cancer patients who are likely to derive big benefits from receiving trastuzumab and lapatinib, and the researchers running the trial think these same women may not need chemotherapy after surgery.

But it’s too early to say this for sure – this needs to be confirmed with longer follow-up and larger clinical trials. And this needs to answer two key questions.

First, researchers and doctors have to come up with a way of identifying those women who are more sensitive to pre-surgery treatment.

Following this, they will need to run clinical trials to see if these women really can avoid chemotherapy treatment and if the current standard of care for some HER2 positive breast cancer patients can and should be changed.

It’s certainly one to keep an eye on.

Aine