Early-stage breast cancer patients whose tumors carry genetic markers associated with a low risk of disease recurrence may not need to undergo chemotherapy, suggests a new study that employed a test devised by a UC San Francisco researcher.
In the study, reported Aug. 24, 2016, in The New England Journal of Medicine, researchers profiled surgically removed tumors from nearly 6,700 patients using a genetic test known as MammaPrint, which predicts the risk of cancer recurrence by measuring the expression of a suite of 70 genes. They found that early-stage breast cancer patients with high “clinical risk” – as determined by conventional measures such as tumor size, the presence of hormone receptors, and metastasis to lymph nodes – but low genetic risk, according to MammaPrint results, had very similar prognoses whether they underwent chemotherapy or not.
After five years, nearly 95 percent of patients with high clinical risk, but low genetic risk, who did not receive chemotherapy were still alive and without metastatic disease distant from the site of their primary cancer, a survival rate only 1.5 percent lower than in women with the same characteristics who did receive chemotherapy. The patients had undergone other standard treatments in addition to surgery, including hormone therapy and radiation treatment.
Potential to Help Clinicians, Patients Evaluate Treatment
The results suggest that MammaPrint testing could be used to help clinicians and patients evaluate their treatment course – which may include skipping chemotherapy.
“For the first time, a prospective, randomized trial shows that the active biology of breast cancer in an individual, as assessed by the MammaPrint test, can assist in making a well-informed choice to undergo chemotherapy treatment or not,” said co-first author Laura van ’t Veer, PhD, an inventor of MammaPrint, and director of Applied Genomics at the UCSF Helen Diller Family Comprehensive Cancer Center.