Combining two powerful breast cancer drugs could dramatically shrink or destroy tumours in just 11 days, British doctors have discovered.
Some patients with HER2 positive breast cancer may be spared chemotherapy altogether if they are given the drugs straight after diagnosis and before they have surgery.
About 15 per cent to 25 per cent of women diagnosed with breast cancer have HER2, which tends to grow more quickly than some other types of breast cancer.
Researchers have discovered that combining the drugs Tyverb (lapatinib) and Herceptin (trastuzumab) and giving them to women before surgery could lead to tumours shrinking significantly or even disappearing.
In a clinical trial, some of the women who responded well to the treatment also had cancer that had already spread to their lymph nodes.
Presenting their findings at the European Breast Cancer Conference in Amsterdam, experts described the findings as exciting.
Prof Nigel Bundred, from the University of Manchester and the University Hospital of South Manchester NHS Foundation Trust, who presented the data, said: "This has groundbreaking potential, because it allows us to identify a group of patients who, within 11 days, have had their tumours disappear with anti-HER2 therapy alone and who potentially may not require subsequent chemotherapy.
“This offers the opportunity to tailor treatment for each individual woman.”
The UK EPHOS-B trial involved 257 women with newly diagnosed HER2 positive breast cancer.
In the first part of the trial, 130 women were randomised to receive either no treatment before surgery or Herceptin and Tyverb for 11 days after diagnosis and before surgery.
In the second part of the study, the next group of 127 women were divided in three, to receive either no treatment, Herceptin only or the combination of Herceptin and Tyverb.
Samples of tumour tissue were taken from the first biopsy, which led to a cancer diagnosis, and again during surgery.
Experts looked to see if there had been a drop in levels of Ki67 protein - an indicator of cells growing and dividing - or a rise in cancer cell death of 30 per cent or more.
Women were found to have had a pathological complete response (pCR) if no active cancer cells could be found, that is, no biological sign of invasive tumour could be found in the breast.
They were said to have minimal residual disease (MRD) if the tumour was less than 5mm in diameter.
Results from the second part of the trial showed that, in addition to a drop in Ki67, 11 per cent of women on combined treatment had pCR and 17 per cent had MRD.
For those women given only Herceptin, 0 per cent had pCR and 3 per cent had MRD.
No patients had either pCR or MRD in the no treatment group.
Trial co-leader Prof Judith Bliss, from the Institute of Cancer Research in London, said it was "unexpected to see quite such dramatic responses . . . within 11 days.
“Our results are a strong foundation on which to build further trials of combination anti-HER2 therapies prior to surgery - which could reduce the number of women who require subsequent chemotherapy, which is also very effective but can lead to long-term side effects.”
At the moment, women usually have their tumour removed during surgery followed by a combination of chemotherapy, radiotherapy, hormonal therapies and targeted drugs such as Herceptin.
According to Cancer Research UK, current treatments are effective, and women often experience a complete response after three to four months.
Nevertheless, researchers said the 11-day response was very surprising.
Prof Arnie Purushotham, senior clinical adviser at Cancer Research UK, which funded the study, said: "These results are very promising if they stand up in the long run and could be the starting step of finding a new way to treat HER2 positive breast cancers.
About 5,300 to 8,000 women a year are diagnosed with HER2 positive breast cancer.