MammaPrint, a 70-gene signature test, might help healthcare providers and patients determine whether they will derive a benefit from chemotherapy, or if they could safely choose to not receive chemotherapy for early-stage breast cancer. These results need to be validated, and compared to other tests in order to confirm findings and determine true clinical utility of its utilization in choosing treatment options. These results were recently published in the New England Journal of Medicine.
Early-stage breast cancer refers to breast cancer that is detected prior to its spread to distant sites in the body, referred to as distant metastasis, or distant recurrence. Historically, chemotherapy was an integral component of a treatment regimen for early-stage breast cancer, as it reduced the risk of a patient experiencing a distant recurrence. However, researchers noticed that some women with early-stage breast cancer derived a much greater benefit from chemotherapy than others. Due to the side effects caused by chemotherapy, research is now aimed at understanding and identifying which patient and cancer characteristics are associated with deriving benefit from chemotherapy, and conversely, those associated with not deriving any benefit from chemotherapy.
MammaPrint is a test that analyzes 70 gene signatures (the sequencing of specific genes) that are associated with different outcomes in early-stage breast cancer. Researchers continue to examine the accuracy of MammaPrint in identifying which patients might safely forego chemotherapy (and thus, its toxic side effects) without increasing their risk of experiencing a cancer recurrence.
Researchers recently conducted a large, phase III clinical trial that included 6,693 women with early-stage breast cancer in an attempt to validate the accuracy of MammaPrint. The trial included women who were either at a high or low risk of developing a cancer recurrence based on a clinical risk assessment (age, size of cancer, aggressiveness of cancer, number of nearby lymph nodes to which the cancer spread, and certain biomarkers).
The group of women who were at a high risk of developing a cancer recurrence based on both a clinical risk assessment, and results from the MammaPrint test were treated with chemotherapy. Conversely, the group of women who were at a low risk of developing a cancer recurrence based on both a clinical risk assessment and results from the MammaPrint test were not treated with chemotherapy.
However, 1,550 women in the trial were considered to be at a high risk of developing a cancer recurrence based on a clinical assessment, but a low risk of developing a cancer recurrence based on the MammaPrint test results. Among these women, one group received treatment with chemotherapy, while the other group did not receive chemotherapy.
- At 5 years, the rate of patient survival without experiencing distant metastasis was 94.7% for those who did not receive chemotherapy.
- The survival difference at 5 years was increased by only 1.5% among patients who received chemotherapy, compared to those who did not receive chemotherapy.
- Hormone-receptor status, HER2 status, and whether the cancer had spread to nearby lymph nodes did not affect the rates of survival without distant metastasis.
The researchers concluded that among women with early-stage breast cancer who are considered to be at a high risk of experiencing a cancer recurrence based on clinical assessment, but a low risk of experiencing a cancer recurrence based on MammaPrint test results, “the receipt of no chemotherapy on the basis of the 70-gene signature led to a 5-year rate of survival without distant metastasis that was 1.5 percentage points lower than the rate with chemotherapy. Given these findings, approximately 46% of women with breast cancer who are at high clinical risk might not require chemotherapy.”
Studies are ongoing as researchers continue to identify genetic and molecular markers that help individualize treatment options for patients with cancer.
Reference: Cardoso F, van’t Veer L, Bogaerts J, et al. 70-gene signature as an aid to treatment decisions in early-stage breast cancer. New England Journal of Medicine. 2016;375:717-729. DOI:10.1056/NEJMoa1602253. Available at: http://www.nejm.org/doi/full/10.1056/NEJMoa1602253. Accessed August 29, 2016.