Gene Assay Reduces Chemotherapy in Younger Breast Cancer Patients

A commercial gene assay has been used to help estimate the likelihood of recurrence in women with early-stage breast cancer and, thus, determine those who may or may not benefit from adjuvant chemotherapy.

The National Comprehensive Cancer Network (Fort Washington, PA, USA) includes the use of the 21-gene assay for women with lymph node-negative, hormone receptor positive (HR+)- and human epidermal receptor 2 negative (HER2-) disease. The majority of women diagnosed with early stage breast cancer each year would be potential candidates for the assay and as technology such as this becomes more available, it is important to note if such tests are used appropriately.

Scientists at the MD Anderson Cancer Center (Houston, TX, USA) carried out a retrospective, population-based study and identified 112,522 patients from the MarketScan research database younger than 65, and 54,186 from the SEER-Medicare database older than 66. In the cohort of younger patients, 13.6% overall underwent Oncotype DX assay (Genomic Health, Inc., Redwood City, CA, USA), and in those that met the test criteria, 60% of women received the diagnostic tool. The scientists also noted that the assay was associated with reduced adjuvant chemotherapy.

In the cohort of women older than 66, 7.2% overall received Oncotype DX; among those patients with HR+, lymph node-negative breast cancer, 67.1% of women underwent testing. However, in this population, testing was not associated with a statistical reduction in the use of adjuvant chemotherapy. In both groups, the investigators found that the use of the assay increased over time, from when the technology was first introduced into practice in 2005 until 2012. Also, particularly in the younger cohort, they noted an increased use of the test in women with node-positive disease. While the tool's use in this setting has shown some promise in retrospective studies, it still needs to be tested prospectively.

Mariana Chavez Mac Gregor, MD, a coauthor of the study and an assistant professor of oncology, said, “In the younger group of breast cancer patients for whom the test is appropriate, and when used in this setting, we're finding an important reduction in chemotherapy use. The contrast between older and younger patients' results did surprise us. However, generally, older breast cancer patients receive much less chemotherapy because of their age and because they often have additional comorbidities. Perhaps we will see that impact with time.” The study was presented at the 2014 San Antonio Breast Cancer Symposium, held December 9–13, 2014, in San Antonio (TX, USA).

Related Links:
US National Comprehensive Cancer Network 
M. D. Anderson Cancer Center 
Oncotype DX