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How trials are making breast cancer radiotherapy smarter and kinder

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Dr Navita Somaiah

Leader, Translational Breast Radiobiology Team at The Institute of Cancer Research, London and Clinical Oncologist at The Royal Marsden NHS Foundation Trust

Researchers have developed and tested new radiotherapy treatment regimens, treating women with breast cancer with fewer daily doses of radiation, whilst minimising side effects and the burden on patients.


Around 63% of patients diagnosed with breast cancer in England receive radiotherapy as part of their primary curative cancer treatment. 

The total dose of radiotherapy given to patients is traditionally divided into small daily doses, called fractions, spread over a number of weeks. For decades the daily dose has remained small in order to keep side effects to a minimum.  

Shorter treatment courses

However, various trials have shown over the last decade that for early breast cancer, a lower total dose is as effective when delivered in fewer, larger fractions, which can be given over a shorter period of time. 

These kinds of dosing schedules are known as ‘hypofractionated’ radiotherapy. These smarter treatments are kinder to patients too; keeping side effects low and reducing the number of times they have to travel to and from hospital.

These smarter treatments are kinder to patients too; keeping side effects low and reducing the number of times they have to travel to and from hospital.

New clinical trials 

A number of clinical trials led by scientists at The Institute of Cancer Research in London and its hospital partner, The Royal Marsden NHS Foundation Trust, assessed the role of hypofractionated radiotherapy for treating women with early breast cancer. 

Historically, women received radiotherapy in 25 daily doses over five weeks. The UK START trials showed that 15 doses, or ‘fractions’, given over three weeks were as safe and effective as 25 fractions given over five weeks – reducing standard treatment to 15 daily doses in three weeks over ten years ago.

Next step trials 

The next step was the FAST trial, which successfully showed that five larger fractions given as one fraction per week could be delivered safely, causing no more changes in the healthy tissues of the breast as 25 small fractions over five weeks. 

FAST laid the groundwork for the FAST-Forward trial, which tested an even shorter treatment course of five fractions of breast radiotherapy delivered in a single week. 

The FAST-Forward trial results confirming safety and efficacy were published just as the COVID-19 pandemic hit, enabling safe delivery of breast radiotherapy to thousands of women who may otherwise have faced delays or interruptions in their treatment. This 5-fraction regimen has now been adopted as the UK standard for patients with early breast cancer.

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