Genetic Test May Reduce the Use of Post-Surgery Chemotherapy in Early Stage Breast Cancer Patients

In an announcement at the AACR annual meeting today, BCRF investigator, Dr. Martine Piccart reported primary results from the international MINDACT Trial that could dramatically reduce the number of early stage breast cancer patients who receive chemotherapy.

The MINDACT TRIAL seeks to determine what patients may avoid chemotherapy by comparing the use of MammaPrint®, a gene-based assay that creates a 70-gene profile to predict which patients are least likely to have a breast cancer recurrence and may forego aggressive chemotherapy, to the standard clinical criteria in selecting early-stage breast cancer patients who do not need chemotherapy. This trial is a prospective, randomized clinical trial involving 6,693 women from 111 clinical centers in nine countries, led by longtime BCRF investigator Dr. Laura Van ’t Veer.

“Oncologists do prescribe to many women with early disease the use of adjuvant [post- surgical] medical therapies, the goal of which is to eradicate the possibility of metastasis. This task is a difficult one associated with many risks, and one of which is overtreatment,” said Dr. Martine Piccart during this morning’s AACR press conference. “The MINDACT TRIAL is the only trial assessing tumor biology against tumor anatomy with a few biological features added in order to reduce the prescription of adjuvant chemotherapy without impairing outcome.”

When considering chemotherapy for early-stage breast cancer, most oncologists will consider clinical and biological criteria including the patient’s age, stage and grade of the tumor, as well as the presence of biomarkers such as the HER2 protein or estrogen and progesterone receptors. Oncologists also balance both the benefits and risks of adjuvant chemotherapies while also considering the socio-economic burden of these decisions.

Participants of the MINDACT trial were categorized as G-high/C-high if they were predicted to be at high risk of recurrence on both the MammaPrint® (genomic) assay (G-high) and on the standard clinical criteria (C-high), G-low/C-low if they were low risk on both assays,  G-high/C-low, if the genomic score predicted high risk, but the clinical cored predicted low risk, and G-low/C-high if the genomic assay predicted low risk and the clinical criteria score predicted high risk.

The study reported at AACR looked at the patients who fell into the ambiguous categories of G-high/C-low and G-low/C-high. Patients in these groups were randomly assigned to receive standard chemotherapy or not.

Among 3,356 patients who were categorized as having a high risk by clinical criteria, but low risk on MammaPrint® (G-low/C-high), following the recommendations of no chemotherapy, based on the MammaPrint® assay reduced the use of chemotherapy by 46 percent with no decrease in the 5-year, metastasis-free survival rate, which was 94 percent for all women in this group, whether they received chemotherapy or not.

Commenting on the study results, Dr. Piccart noted that when considering all the patients who were enrolled in the MINDACT study, 14 percent could avoid chemotherapy by using MammaPrint® gene test to assess risk of recurrence compared to those relying on the traditional clinical parameters.

“The MINDACT trial results,” she said, “provide Level 1 clinical evidence that using MammaPrint®  could change clinical practice by substantially re-escalating the use of adjuvant (post-surgery) chemotherapy and sparing many patients an aggressive treatment they will not benefit from.”

The MINDACT trial was supported in part by BCRF.