Ductal Carcinoma in Situ (DCIS) is the earliest form of breast cancer (stage 0) and the most common type of non-invasive breast cancer.

DCIS affects women all around the world. It is a condition in which abnormal cells are contained within the milk ducts of the breast. It is not an invasive breast cancer but if left untreated, it may turn into an invasive breast cancer.

DCIS is a growing health problem since mammographic screening is widely available in many countries. Today, it accounts for up to 25% of new breast cancer diagnoses. However, in contrast to invasive breast cancer, there has been comparatively little research on DCIS. As a result, there are often uncertainties on how individual patients with DCIS may best be managed, especially to reduce the risk of their DCIS from becoming an invasive breast cancer.

• After surgery alone, about one third of DCIS will recur, of which approximately half would be in the form of invasive breast cancer with the potential to spread to other organs.

• If left untreated, 40-70% of DCIS may develop into invasive breast cancer.

• Radiotherapy to the breast reduces the risk of recurrence but may lead to significant over-treatment in some patients and unnecessary costs.

The study objectives are

• Better patient outcomes: to improve the safety and the quality of DCIS treatment, and to tailor treatment intensity according to each patient’s individual risk of developing invasive breast cancer. The goal is to minimise the risk of developing invasive breast cancer in patients with high-risk DCIS, and spare unnecessary treatment side-effects in low-risk patients.
• Practice-changing potential and scientific advances: if biomarkers for recurrence can be identified, a molecular signature test for DCIS could be developed so that doctors can recommend the most appropriate therapy to patients, tailored to their individual risks of recurrence. The study will substantially advance knowledge about how DCIS progresses to invasive breast cancer.
• Social benefits: The results of the study could lead to significant cost savings for healthcare systems by minimising over or under-treatment of patients with DCIS.

DCIS (BIG 3-07 / TROG 07.01) is an international study that aims to:

– investigate if, after breast conserving surgery, higher radiation doses (“boost”) to the part of the breast where the DCIS was, in addition to radiotherapy of the whole breast, would further improve tumour control;

– investigate if a shorter course of radiotherapy (3 weeks) is as effective as the usual longer course (5 weeks) to improve patient convenience;

– identify a molecular signature that predicts individual risk of recurrence to personalise treatment.

The 5-year analysis results were presented by Dr Boon Chua, study Principal Investigator, at the San Antonio Breast Cancer Symposium (virtual SABCS 2020, 8-12 December, Texas, USA).

The 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.

Read the press release issued on 9 December 2020

1. The study of patients with DCIS treated with breast conserving surgery will examine:
– The duration of whole breast radiation (3 weeks versus 5 weeks)
– Whole breast radiation plus a radiation boost for patients with a high risk of recurrence

2.  Using the patient data and tumour blocks collected, researchers will work to identify biomarkers to predict which patients are at high risk of recurrence and may require more intensive treatment; and which patients are at low risk of recurrence and may require less treatment.  Findings from this research can help tailor treatment to individual patients diagnosed with DCIS in the future.

Patients aged 18 and older, with a confirmed diagnosis of DCIS, without invasive breast cancer.
In total, 1,608 patients were recruited.

Patients from Australia, Belgium, the Netherlands, France, Switzerland, Italy, the United Kingdom, Ireland, New Zealand, Singapore and Canada are participating in this large clinical trial.

Coordinating group and study sponsor: Trans-Tasman Radiation Oncology Group (TROG) 

The study was extended to European and non-European countries through the BIG network.

Participating groups:

Canadian Cancer Trials Group (CCTG)
European Organisation for Research and Treatment of Cancer (EORTC)
Scottish Cancer Trials Breast Group (SCTBG)
International Breast Cancer Study Group (IBCSG)
Cancer Trials Ireland (CT-IRE)

• The 1.608 patients were recruited in June 2014, two years ahead of schedule.

• Patients will be followed for at least 10 years after enrolment.

• The identification of biomarkers of recurrence will take 5 years.

The study’s main results were presented in 2020 and the final analysis is planned for 2024.

Read the press release issued on 9 December 2020

136 centres worldwide in 11 countries from six BIG member groups participate in this study

Not at present.

The study is funded by the Australian National Health and Medical Research Council, Susan G. Komen for the Cure®, Breast Cancer Now, OncoSuisse Swiss Federation Against Cancer, Dutch Cancer Society and Canadian Cancer Society.

NCT00470236