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MammaPrint Shows Which Breast Cancer Patients Can Skip Chemo

MammaPrint Shows Which Breast Cancer Patients Can Skip Chemo

Results Relevant for the United States

Approached for comment, Clifford Hudis, MD, chief of the breast medicine service at the Memorial Sloan Kettering Cancer Center in New York City, told Medscape Medical News that the new data from Europe “are relevant for the United States.”

“One of the drivers of the use of another test, the Oncotype Dx, was the availability of data suggesting that it could be used to select for or against the addition of chemotherapy to endocrine adjuvant treatment in hormone-receptor-positive disease,” he said. With the new data, the MammaPrint test “may be able to fulfill a similar role in helping guide clinicians to a better treatment decision for each individual patient.”

“A key aspect of this new result is that it may provide additional evidence that genomic tests really can play a role in everyday practice for patients with early-stage breast cancer,” Dr Hudis said.

Details of the Results

When the MINDACT trial began in 2007, it recruited patients with early-stage breast cancer and negative lymph nodes, but the protocol was changed in 2009 to also allow patients with one to three positive nodes, Dr Piccart noted. In the overall trial population, about one in five patients had node-positive disease, she noted, and about 10% of tumors were HER2-positive, which are biologically aggressive.

The genomic test was compared with clinical assessment using Adjuvant! Online, and women were classed into one of four categories.

Women who were assessed as low risk by both genomic and clinical tests — i.e., G-low, C-Low (n = 2743; 41%) — did not received chemotherapy, and the results show that they had the best outcomes, with a distant-metastasis-free survival at 5 years of 97.6%.

Women who were assessed as high risk by both measures — i.e., G-high and C-high (n = 1807; 27%) — were strongly encouraged to have chemotherapy, but despite this, they had the worst outcomes, with a distant-metastasis-free survival rate at 5 years of 90.6%.

The main part of the trial focused on the women in which the results were discordant, having been assessed as high risk by one measure but low risk by the other, and these patients were randomized to receive chemotherapy or not (anthracycline or taxane regimens). Patients also received endocrine therapy (tamoxifen for 2 years followed by letrozole for 5 years or letrozole for 7 years).

The outcomes in these two discordant groups were similar, with a distant-metastasis-free survival rate at 5 years of 94.8% in women assessed as C-high, G low (n = 1550; 23%), and a rate of 95.1% in women assessed as C-low, G-high (n = 592; 9%).

The curves for patients who did receive chemotherapy were almost superimposable on those who did not, Dr Piccart said, suggesting that there was no benefit from the chemotherapy.

“We know that not all patients who currently receive adjuvant chemotherapy need the treatment, and they endure significant adverse side effects without gaining clinical benefits,” Dr Piccart commented. These new results show that use of this genomic assay helps to identify those patients that can skip chemotherapy, even if they are assessed clinically as being high risk.

In his discussion, Dr Burstein said the implications from MINDACT and other recent related trials are that “most ER-positive HER2-negative stage I and II cancers, including N1, warrant tumor genomic profiling for optimal decision making, in particular choosing whether to receive chemotherapy.”


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