Dr Konstantinos Tryfonidis, a clinical research physician at EORTC, presented the outcome results from the EORTC 10041/BIG3-4 (MINDACT trial) at the ESMO 2017 congress.

The study showed that one in four patients with small breast cancers exhibited an aggressive phenotype based on the 70-gene signature (MammaPrint) and these patients may profit from chemotherapy.

The subanalysis included the 826 patients in MINDACT with a primary tumour size of less than 1 cm (pT1abpN0). Clinical and genomic risks were assessed and 196 patients (24%) were found to be at low clinical risk and high genomic risk. These patients were randomised to receive, or not receive, chemotherapy.

Results report that 5-year distant metastasis free survival for patients with low clinical risk and high genomic risk, pT1abN0 tumours, who received chemotherapy, was 97.3% vs 91.4% for those who did not. And 5-years overall survival for these patients treated with chemotherapy was 98.5% vs 95.8% for those who did not receive it, showing possible benefits from chemotherapy for these tumours that have an aggressive phenotype.

“We found that nearly one in four patients with small tumours are at risk of distant metastases and do benefit from chemotherapy,” said Dr Fatima Cardoso, Co-Principal Investigator of MINDACT, Chair of the EORTC Breast Group and Director of the Breast Unit of the Champalimaud Clinical Centre, Lisbon, Portugal. “This was striking because based on clinical criteria alone you would say that these tumours are not aggressive and therefore patients do not need chemotherapy. But 23.7% of small tumours had an aggressive biology, which shows that not all small tumours are the same.”

Should it be recommended that all patients with small node-negative early stage breast cancer (pT1abN0), even those considered as low risk as per clinico-pathological criteria, undergo a genomic test to determine the biological profile of their tumour?

“We cannot draw conclusions based on this analysis,” said Tryfonidis. “It is important to mention that this is an exploratory analysis in a small subset of the total MINDACT population, consisting of patients which have overall a favourable disease outcome. The use of the genomic test in patients with such tumours should always be considered on a case by case discussion, taking always into account other important parameters including patient preferences.”

The MINDACT (Microarray In Node-negative and 1 to 3 positive lymph node Disease may Avoid ChemoTherapy) study is managed and sponsored by the EORTC in collaboration with the Breast International Group (BIG) and TransBIG Consortium. The study includes 6,693 women with early stage breast cancer (lymph node negative or 1-3 lymph node positive). As previously reported, MINDACT showed that around 46% of patients who were at high clinical risk for recurrence, defined using a modified version of Adjuvant! Online may not require chemotherapy. These women had a low genomic risk for recurrence according to MammaPrint, a genomic signature that improves prediction of clinical outcome in women with early stage breast cancer.