4 March 2025: A decade on from the last participant completing treatment, the BIG 3-07/TROG 07.01 – DCIS trial is continuing to deliver valuable results.

Led by TROG Cancer Research, the international, randomised phase III study aimed to improve the treatment outcomes of women diagnosed with ductal carcinoma in-situ (DCIS) of the breast.

DCIS of the breast is characterised by abnormal cells in the milk ducts that haven’t spread into the breast tissue, but in some patients, the DCIS may progress to become invasive breast cancer. Despite it being a common diagnosis, there has been relatively little research to improve the treatment outcomes of women with DCIS.

While radiotherapy after breast conserving surgery reduces the risk of invasive recurrence, it has short- and long-term toxicity. There has long been a lack of high quality evidence on the optimal radiation dose-fractionation for DCIS, to guide patients and clinicians in achieving treatment goals.

The DCIS trial aimed to shed light on the long-term efficacy and safety of different radiation doses and number of radiation therapy sessions to reduce the risk of recurrence and improve the safety and convenience of care for women with DCIS.

The first patient was enrolled in the study in 2007, and recruitment of 1608 patients from 118 centres across 11 countries was completed in 2014, two years ahead of schedule. A substudy focusing on quality of life closed to recruitment in 2013, after accruing 1213 patients. A network of biobanks in Australia, Canada, Italy and the UK have been in operation since study inception to enable the conduct of translational research focusing on biomarkers that predict the progression of DCIS to invasive breast cancer.

Several impactful papers detailing findings of the DCIS trial have already been published, including five-year analysis published in The Lancet in 2022. It demonstrated that boost radiation after postoperative whole breast irradiation improved local control of the disease in patients with non-low-risk DCIS, although there was an increase in toxicity experienced among those receiving the additional radiation therapy.

In 2024, the research team led by Chief Investigator Prof Boon Chua, from UNSW, was awarded a $1.128 million NHMRC grant for the final stage of the trial – 10-year analysis of the study endpoints, as well as an additional, novel qualitative study.

“This award enables continuation of our productive global collaboration to carry the trial to a successful conclusion. It will also support our new qualitative study to explore the lived experiences of the diagnosis, treatment and survivorship 10 years post-randomisation.” Prof Chua said. “Collectively, our studies will generate the data to underpin development of a risk assessment tool and decision aid for women with DCIS.”

That research is now underway to provide further valuable evidence to improve experiences and outcomes for women with DCIS.

The DCIS trial is led by TROG Cancer Research, and conducted in collaboration with Breast International Group (BIG 3-07); Canadian Cancer Trials Group (CCTG MA33); European Organisation for Research and Treatment of Cancer (EORTC Trial 22085-10083); Scottish Cancer Trials Breast Group (SCTBG); Cancer Trials Ireland (CTI); and the International Breast Cancer Study Group (IBCSG38).