- 30 August 2022 - 

Primary results of DCIS published in The Lancet

The DCIS study (BIG 3-07/TROG 07.01) is an academic, investigator-led, randomised phase III study of radiation doses and treatment schedules in patients with non-low risk DCIS of the breast.

Ductal carcinoma in situ (DCIS) of the breast is characterised by abnormal cells in the milk ducts which have not spread into the breast tissue. The international DCIS study shows that after breast conserving surgery, higher radiation doses to the part of the breast where the DCIS was found, in addition to radiotherapy of the whole breast, significantly reduced its risk of returning in patients with higher-risk DCIS. Compared to 5 weeks of whole breast radiotherapy, the study also shows that the shorter, more convenient 3 weeks of radiotherapy did not increase recurrence.

These primary results have recently been published in The Lancet (6 August 2022), which concludes:

“In patients with resected non-low-risk DCIS, a tumour bed boost after whole breast irradiation (WBI) reduced local recurrence with an increase in grade 2 or greater toxicity. The results provide the first randomised trial data to support the use of boost radiation after postoperative WBI in these patients to improve local control. The international scale of the study supports the generalisability of the results."

This achievement demonstrates that research on DCIS is a high priority for many patients and researchers. The ongoing challenge is to ensure that this academic study is completed successfully, as the study patients need to be followed-up for 10 years in order to achieve the purpose of the study. Considerable resources are required for the study to yield meaningful practice-changing outcomes, particularly to obtain the cutting-edge biomarker information that will allow personalised treatment of patients with DCIS.

Practice-changing potential, scientific advances and social benefits

Tailoring radiation doses and number of treatments to the recurrence risks in patients undergoing radiotherapy for DCIS after surgery are of intense international interest. The study is one of the few large-scale clinical trials in DCIS that used highly standardised protocols for radiation treatment, detailed patient data collection, robust quality assurance, and development of one of the world’s largest DCIS tissue resource. Collectively, this comprehensive study has the potential to generate the high-quality evidence necessary for improving radiotherapy in patients with DCIS to improve patient outcomes.

Research using the unique DCIS resource of the study may identify markers for recurrence, in particular invasive recurrence. If this future research is successful, a test could be developed to predict the recurrence risks of DCIS and guide treatment decisions by patients and clinicians. 

Final analysis of the DCIS study is planned for 2024. The successful conduct to date of this academic, investigator-led study is made possible only by the strong and enduring international alliance of the BIG network.

Chua B, Link Emma K, Kunkler Ian H, et all. Radiation doses and fractionation schedules in non-low-risk ductal carcinoma in situ in the breast (BIG 3–07/TROG 07.01): a randomised, factorial, multicentre, open-label, phase 3 study.
The Lancet, VOLUME 400, ISSUE 10350, P431-440, August 06, 2022. 2022DOI: