Case study: Understanding how radiotherapy affects long-term breast cancer patient outcomes
Overview
Every year, approximately 55,000 women and 370 men receive breast cancer diagnoses in the UK.
Many breast cancer patients (63%) receive radiotherapy as part of their treatment. Radiotherapy delivers concentrated radiation doses to the breast area to eliminate any cancer cells that remain after surgery.
Despite its widespread use, the long-term impact of radiotherapy on patient outcomes was not well understood. Around 5% of patients experience recurrence within 10 years of breast-conserving surgery, but until this study there had been no long-term randomised evidence examining whether radiotherapy influenced outcomes beyond this period.
The Scottish Breast Conservation Trial examined whether treatment of early breast cancer patients with radiotherapy has an impact on long-term survival in patients with early-stage breast cancer. The research team followed 585 patients over a 30-year period through a randomised controlled study. Following surgery patients received chemotherapy or tamoxifen depending on whether their cancer was hormone-driven by oestrogen, with half of the participants also receiving radiotherapy.
Patients were followed using electronic and paper NHS medical records.
Who is involved?
The 30-year project was led by The University of Edinburgh, in partnership with Public Health Scotland (eDRIS), the Edinburgh Breast Unit, and the Queen Elizabeth University Hospital. All 14 participating institutions were NHS hospitals located in Scotland. The project was funded by the Breast Cancer Institute and PFS Genomics (now part of Exact Sciences).
What have they found?
The study found that radiotherapy combined with chemotherapy or tamoxifen after breast-conserving surgery reduces the risk of breast cancer returning within 10 years. It also showed that postoperative breast radiotherapy has a 'ceiling effect' with little impact on risk of local recurrence after 10 years, or on overall survival after 30 years.
A 16 gene molecular signature, POLAR (Profile for the Omission of Local Adjuvant Radiotherapy), is not only prognostic for locoregional recurrence but also predictive of benefit from RT in selected patients. However, further studies are needed to validate POLAR in this setting
Why are long-term studies important?
Decades-long studies like this are vital to inform future treatment strategies. According to Dr Linda Williams, Senior Research Fellow in Medical Statistics at the University of Edinburgh, “This 30-year study marks the longest follow-up of postoperative radiotherapy in the treatment of early-stage breast cancer. Long-term studies like this, which go beyond 10 years of follow up, are crucial to fully assess the risks and benefits of treatments.”
Key achievements
- Investigating the prognostic and predictive value of a molecular signature of breast cancer radiosensitivity in a meta-analysis including patients from the Scottish conservation trial.
- Conducting one of the longest follow-up studies of patients with early breast cancer in a randomised trial of breast-conversing therapy.
- Demonstrating that radiotherapy combined with chemotherapy or tamoxifen after breast conserving surgery reduces the risk of breast cancer returning within 10 years.
- Showing that postoperative breast radiotherapy has a 'ceiling effect' with little impact on risk of local recurrence after 10 years, or on overall survival after 30 years.
- Demonstrating that POLAR is not only prognostic for locoregional recurrence, but also predictive of benefit from radiotherapy in selected patients.
“Our evidence suggests that radiotherapy protects against cancer returning in the same breast for up to 10 years. It supports the continued use of radiotherapy after breast-conserving surgery for most patients with early breast cancer.”
Image credit: Breast cancer cells. Anne Weston, Francis Crick Institute. Source: Wellcome Collection.