The results of the Cancer Research UK-funded trial, presented at the 10th European Breast Cancer Conference in Amsterdam, could – if successfully replicated – lead to fewer women needing chemotherapy.
“This offers the opportunity to tailor treatment for each individual woman.”
Around a quarter of 66 women with HER2 positive breast cancer treated for 11 days with both trastuzumab (the generic name for Herceptin) and lapatinib saw their tumours rapidly shrink significantly or even disappear.
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.
Samia al Qadhi, chief executive at Breast Cancer Care, said: “The astonishing findings in this study show that combining these two drugs has the potential to shrink HER2 positive breast cancer in just 11 days.
“For some HER2 positive breast cancer patients the effect of this drug combination will be amazing and mean they can avoid chemotherapy and its gruelling side effects completely. For others, their tumours may not shrink, but doctors will know either way very quickly, giving them the ability to rapidly decide on further treatment.
“Although an early study, this has game changing potential. Yet before this can be made available we need to see more evidence. Particularly because, at present, trastuzumab’s (Herceptin) licensing means it is only available to be used alongside chemotherapy and not alone. All cancer patients deserve access to clinically effective treatments.”
Trial co-leader Prof Judith Bliss, director of the clinical trials and statistics unit at the Institute of Cancer Research, London, said: “It was unexpected to see quite such dramatic responses to the trastuzumab and lapatinib 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.”
The trial, led by researchers from Manchester University, the University Hospital of South Manchester NHS foundation trust and the Institute of Cancer Research, studied 257 women with HER2 positive breast cancer in the short gap between their initial diagnosis and surgery to remove their tumours.
Initially women were randomised to receive either trastuzamab or lapatinib or no treatment. Halfway through the trial, after evidence from other trials of the effectiveness of the combination, the design was changed so that additional women allocated to the lapatinib group were also prescribed trastuzumab.
Of the women receiving both, 17% had only minimal residual disease – defined as an invasive tumour smaller than 5mm in size – and 11% had no biological sign of invasive tumour in the breast. Of the women treated with trastuzumab only, 3% had residual disease or complete response.
Current treatments are effective, and complete response is common after three to four months, but observing a disease response so quickly took the researchers by surprise.
In the UK, around 53,000 women a year are diagnosed with invasive breast cancer, and in 10% to 15% of these cases it is HER2 positive breast cancer. Around 11,500 women die from the disease every year.
Herceptin was approved by the National Institute for Health and Care Excellence (Nice) 10 years ago after pressure from patients. Lapatinib has not been approved and so is not routinely available on the NHS due to its expense.
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, 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.
“This could mean some women can avoid chemotherapy after their surgery – sparing them the side-effects and giving them a better quality of life.”