MammaPrint genetic testing for prediction of long-term breast cancer outcomes

This study investigated the accuracy of the 70-gene signature (MammaPrint) genomic profiling test in predicting metastasis and long-term outcomes among breast cancer patients.

Gene-expression signature tests, such as MammaPrint, were developed in order to assess the biological action, and therefore the aggressiveness, of cancers. The idea behind gene-expression signature tests is to identify patients who would benefit from aggressive treatment, such as additional chemotherapy after surgery for example, and to allow tailoring of an optimal treatment plan for each individual patient.

The MammaPrint genetic profiling test was extensively investigated, and validated, as a predictor of cancer progression after surgery in several retrospective studies. However, the accuracy of MammaPrint as a predictor of long-term outcome has not yet been thoroughly investigated.

The current study analyzed the long-term outcomes of 295 women previously evaluated by MammaPrint in a separate study, and currently followed for an average of 18.5 years. MammaPrint results were classified as high or low risk for breast cancer metastasis (cancer spread). All patients were treated with surgery, followed by additional treatments such as radiotherapy, chemotherapy and/or hormonal therapy as indicated by treatment guidelines at the time of therapy.

Of the 295 patients, MammaPrint indicated low-risk of metastasis among 115 patients, and a high-risk of metastasis among 180 patients. Overall, 121 patients developed distant metastasis over the follow-up period, and death as result of breast cancer was seen among 114 patients. The follow up showed a significant difference in the risk of cancer metastasis and overall survival between high and low risk MammaPrint patients. 60.4% of low-risk patients according to MammaPrint were metastasis free 25 years following treatments, compared to 41.6 % of high-risk patients. Overall survival rates 25 years following treatment were 57.3% for low-risk patients according to MammaPrint, compared to 44.5% among high-risk patients. These differences were found to be significant for patients both with, and without, lymph-node involvement.

The predictive power of MammaPrint on metastasis-free survival was found to be highest during the first 5 years following treatment, while the predictive power of MammaPrint on overall survival was found to be most accurate during the first 15 years following treatment.

This long-term follow-up study concluded that MammaPrint is an effective predictor of metastasis and survival up-to 25 years following treatment.

Several of the authors of this study are shareholders or employees of Agendia NV, which markets 70-gene signature (MammaPrint).