EBCC-11: MINDACT Trial: Patients With Early Breast Cancer and Risk of Locoregional Recurrence

Key Points

  • Women who had breast-conserving surgery had an overall 2.1% risk of recurrence by 5 years; if they had a low 70-gene signature score, the risk dropped to 1.4%, whereas if they had a high score, the risk was 3.6%.
  • Among women who had a mastectomy, the overall risk of recurrence was 2.5%, but this dropped to 0.7% in those with a low genetic score and went up to 4.9% in those with a high score.
  • After full statistical analysis, tumor grade and size were the only factors significantly associated with the risk of locoregional recurrences.

Women with small, low-grade, well-defined breast tumors and a genetic profile that shows they are at low risk of the cancer metastasizing have only a 1.4% risk of locoregional recurrence within 5 years, according to new results from a large randomized trial of nearly 7,000 patients. This low risk of locoregional recurrence was seen regardless of whether the women had a mastectomy or breast-conserving surgery.

Presenting the latest results from the MINDACT trial (Abstract 2) at the 11th European Breast Cancer Conference (EBCC-11), Emiel Rutgers, MD, PhD, FRCS, a surgeon at the Netherlands Cancer Institute, said the findings meant that it was possible to identify women who could safely avoid not only chemotherapy after surgery, but possibly also radiotherapy.

“These findings show that, for these selected women, breast conservation is as good as mastectomy, and the risk of relapse is so low that we should look for ways of giving them less aggressive treatment. For instance, even though radiotherapy reduces the risk of locoregional recurrence two- to threefold, can we do without it in some selected patients, such as these low-risk women, and also in some women aged over 50 with small tumors (< 2 cm in diameter) who have a 1.4% risk of relapse within 5 years as well,” said Dr. Rutgers.

Method

Among 6,693 patients enrolled in the MINDACT trial, 5,470 (82%) underwent breast-conserving surgery, and 1,223 (18%), mastectomy. Decisions on how the women were treated were made on the basis of the tumor characteristics (size, grade, hormonal and HER2 status, and whether the disease had spread to any lymph nodes). In addition, their genetic makeup was investigated using the 70-gene signature test MammaPrint, which analyzes the activity of certain genes in early breast cancer and has been shown to accurately predict the risk of cancer metastasizing within 5 or 10 years.

Women who were at low risk of a recurrence based on these clinical and genomic factors did not receive chemotherapy after surgery, whereas those who were at high risk did. Women with a mixture of high- and low-risk factors were randomized to receive chemotherapy or not. Almost all women who had breast-conserving surgery—but not all of the women who had a mastectomy—also had radiotherapy.

Findings

In this latest part of the study, Dr. Rutgers and his colleagues looked at the rate of locoregional recurrences 5 years after surgery and analyzed them according to clinical and genetic characteristics. They found that women who had breast-conserving surgery had an overall 2.1% risk of recurrence by 5 years; if they had a low 70-gene signature score, the risk dropped to 1.4%, whereas if they had a high score, the risk was 3.6%.

Among women who had a mastectomy, the overall risk of recurrence was 2.5%, but this dropped to 0.7% in those with a low genetic score and went up to 4.9% in those with a high score. After full statistical analysis, tumor grade and size were the only factors significantly associated with the risk of locoregional recurrences.

Dr. Rutgers said, “The importance of this MINDACT analysis is that local and regional control, in which breast cancer does not come back in the preserved breast, or in the skin after mastectomy, or in the surrounding lymph nodes, is extremely good. The odds of the cancer coming back are about 2% in 5 years after breast conservation and 2.5% after mastectomy. This includes relapses in the surrounding lymph nodes. This very low risk is determined by the biology of the primary cancer, such as grade, size, and growth pattern, and to some extent also by age, with women over 50 years also having a lower overall risk. Among these women aged over 50, those with slow-growing ‘lazy’ breast cancers have a 0.88% risk, and those with more aggressive ones have a 3.5% risk at 5 years. We should remember that some 10 to 15 years ago, a 10% recurrence rate at 10 years was considered the norm.”

He concluded: “Another important message from these findings is that well-performed breast-conserving surgery in women with good indications is as good as mastectomy.” 

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®.


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