TRIAL UPDATE: 29 July 2025

A large international study focusing on radiation therapy for ductal carcinoma in situ (DCIS) of the breast has reached a significant milestone, with the database locked this month, 18 years after the first trial site was opened for recruitment.

The randomised phase III study investigated 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 BIG 3-07/TROG 07.01 DCIS study in 2007, and recruitment of 1,608 study participants from 118 centres across 11 countries was completed in 2014, two years ahead of schedule.

A network of biobanks in Australia, Canada, Italy and the UK have also been in operation since study inception, to enable translational research focusing on biomarkers that predict the progression of DCIS to invasive breast cancer. A substudy focusing on patient reported outcomes to better understand the perspectives of patients with DCIS and guide shared treatment decision-making completed recruitment of 1,213 patients in 2013. Significant bodies of work have been undertaken by international expert panels to centrally review the pathology, radiation therapy quality, and cosmetic outcomes of study participants to ensure a high standard of study conduct.

On 1 July 2025, the DCIS trial database was officially locked, a decade on from the last study participant completing treatment.

We congratulate the Study Chair and Principal investigator Professor Boon Chua from UNSW Sydney, and thank all the collaborative groups and researchers who have worked tirelessly on the BIG 3-07/TROG 07.01 study over the past 18 years.

Above: Map showing sites participating in the DCIS study

The study was coordinated by TROG Cancer Research and conducted in collaboration with the Breast International Group (BIG 3-07) network of academic research groups including 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).

Several impactful papers have been published detailing the study findings, including results of the five-year analysis published in The Lancet in 2022. This showed that tumour bed boost radiation after postoperative whole breast irradiation significantly reduced recurrence in patients with non-low-risk DCIS but increased some treatment side-effects. The finding that a shorter course of 16 radiation therapy sessions was as safe and effective as the longer course of 25 sessions would help to reduce treatment burden for patients.

The BIG 3-07/TROG 07.01 study has been funded by multiple competitive research grants totalling $6.6 million, and in-kind support of the collaborating groups. Last year, Professor Chua’s research team was awarded a $1.13 million NHMRC grant for the final stage of the randomised trial – 10-year analysis of the study endpoints, as well as a novel qualitative study to explore the lived experiences of the diagnosis, treatment and survivorship among women in the DCIS study.

This research is underway to provide further evidence to improve the outcomes and experiences of women diagnosed with DCIS of the breast.

• Read more about the DCIS trial