Even small tumors in the breast can be aggressive, according to a study in patients with early-stage breast cancer presented at the 2017 European Society for Medical Oncology (ESMO) Congress in Madrid (Abstract 150O_PR). Researchers found that 24% of small tumors were aggressive, and patients benefited from chemotherapy. Aggressive tumors could be identified by a 70-gene signature test (MammaPrint).
“Our results challenge the assumption that all small tumors are less serious and do not need adjuvant chemotherapy,” said lead author Konstantinos Tryfonidis, MD, a researcher at the European Organisation for Research and Treatment of Cancer (EORTC), Brussels.
The MINDACT study is managed and sponsored by the EORTC in collaboration with the Breast International Group (BIG) and included 6,693 women with early-stage breast cancer (lymph node–negative or 1-3 lymph node–positive).
As previously reported by Cardoso et al in The New England Journal of Medicine, MINDACT showed that approximately 46% of patients who were at high clinical risk for recurrence, defined using Adjuvant! Online, might not require chemotherapy. These women had a low genomic risk for recurrence according to the 70-gene signature test.
The subanalysis presented at the ESMO Congress included the 826 patients in MINDACT with a primary tumor size < 1 cm (pT1ab, pN0). 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 randomized to receive or not receive chemotherapy.
The researchers found that at 5 years, very few patients who received chemotherapy experienced disease relapses and showed high rates of distant metastasis–free survival, disease-free survival, and overall survival, which confirms that they derived benefit from chemotherapy.
“We found that nearly one in four patients with small tumors are at risk of distant metastases and do benefit from chemotherapy,” said Fatima Cardoso, MD, senior author of the study, Co-Principal Investigator of MINDACT, and Director of the Breast Unit of the Champalimaud Clinical Centre, Lisbon. “This was striking, because based on clinical criteria alone, you would say that these tumors are not aggressive, and therefore patients do not need chemotherapy. But 24% of small tumors had an aggressive biology, which shows that not all small tumors are the same.”
Commenting on the results for ESMO, Evandro de Azambuja, MD, PhD, Head of the Medical Support Team, Academic Promoting Team, Jules Bordet Institute, Brussels, said: “This study shows that it’s not only tumor size that is important for breast cancer patients, but also tumor biology. All tumors in the study were small—less than 1 cm—and the lymph nodes were free of cancer (node-negative), which in principle should be a signal of good prognosis. But nearly one in four patients—those identified as genomic high-risk—derived benefit from chemotherapy.”
Dr. de Azambuja added: “Small node-negative tumors can be very aggressive, even if they are classified as clinical low risk. Tumor biology needs to be taken into account when deciding adjuvant treatments in this patient population. One cannot forget the patient’s age, performance status, comorbidities, and preferences during the discussion.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.