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Breast Cancer – Even small tumours can be aggressive

Researchers found that nearly one in four small tumours (less than 1 cm) were aggressive and patients benefited from chemotherapy. Aggressive tumours could be identified by a 70-gene signature.

“Our results challenge the assumption that all small tumors are less serious and do not need adjuvant chemotherapy,” said lead author Dr Konstantinos Tryfonidis, a researcher at the European Organisation for Research and Treatment of Cancer (EORTC), Brussels, Belgium.

The MINDACT study included 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, might not require chemotherapy. These women had a low genomic risk for recurrence according to MammaPrint®, a genomic signature that assists in predicting clinical outcomes in women with early stage breast cancer.

A sub analysis presented at ESMO 2017 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 clinical low risk and genomic high risk. These patients were randomised to receive, or not receive, chemotherapy.
The researchers found that at five years, very few patients who received chemotherapy experienced disease relapses, showing high rates of distant metastases-free survival, disease-free survival and overall survival, which confirms that they derived benefit from chemotherapy.
The 5-year rates of distant metastasis-free survival (DMFS) for patients with Cinical Low/Genomic High risk pT1abN0 tumors who received CT was 97.3% vs 91.4% for those who did not. The 5-year distant metastases-free interval (DMFI) and OS for these patients treated with CT were 98.8 % and 98.5 % vs 91.4 % and 95.8 % respectively for those who did not receive CT, showing clearly that biological characteristics can be used as determinants of adjuvant CT administration for T1abN0 tumors.

Tryfonidis K et al., abstract 150O_PR: Not all small node negative (pT1abN0) breast cancers are similar: Outcome results from an EORTC 10041/BIG 3-04 (MINDACT) trial substudy