Los Angeles: Reseachers have developed a molecular test which can pinpoint which patients are at low risk of death from breast cancer even 20 years after diagnosis and tumour removal. As a result, “ultralow” risk patients could be treated less aggressively and overtreatment avoided, leading to fewer toxic effects, researchers said. “This is an important step forward for personalising care for women with breast cancer,” said Laura J Esserman, from the University of California, San Francisco in the US.
“We can now test small node-negative breast cancers, and if they are in the ultralow risk category, we can tell women that they are highly unlikely to die of their cancers and do not need aggressive treatment, including radiation after lumpectomy,” said Esserman. This is the first evidence that it is possible to run a diagnostic test at the time of diagnosis and identify ultralow risk tumours. “This is an exciting advance because approximately 20-25% of tumours diagnosed today may be ultralow risk,” said Esserman.
In the study published in the journal JAMA Oncology, researchers sought to determine whether a 70-gene test could accurately and reliably identify tumours with indolent, or slow-growing, behaviour to assess the risk of cancer recurrence up to 20 years after diagnosis. The same test had shown last year that nearly half of early-stage breast cancer patients, who met traditional criteria for high risk, could safely skip chemotherapy based on the biological makeup of their tumours.
Researchers disclosed that the test, called MammaPrint, tests for a 70-gene signature that can predict whether cancer will recur in early-stage breast cancer patients. In the new analysis, they sought to assess breast cancer patients over 20 years, and to find cancers with no- or almost no-risk for metastatic progression. They collaborated with the Stockholm breast cancer study group (STO) low-risk trial included which 1,780 lymph-node- negative patients with tumours less than or equal to three centimetres in diameter, randomised to two years of adjuvant tamoxifen versus no adjuvant treatment.
Adjuvant therapy is a treatment provided after the initial surgery or treatment, with the intent to suppress recurrent tumour formation. All the women had their tumours surgically removed. The researchers used these tissues to profile a total of 652 women, of whom 311 had received tamoxifen, and 339 had not received adjuvant systemic therapy. The majority of the women (79%) had received mastectomies and lymph node removal – the data did not include cases with less aggressive local therapy.
The multigene test classified 42% of the patients as high-risk, and 58% as low-risk. Researchers found that low-risk patients had a 95% survival rate at 5 years, but many later died from their disease. The test classified 15% (98) of the cases as ultralow risk. The women with ultralow risk tumours had an excellent prognosis, whether or not they used tamoxifen for two years, researchers said. The results suggest that the 70-gene test can be used to help physicians and patients determine their treatment course, and to inform choice of systemic therapy as well as local therapy.