Information derived from a breast cancer assay helped quantify a woman’s risk of developing an ipsilateral breast event (IBE) after undergoing surgical excision for ductal carcinoma in situ (DCIS) without radiation, recent research demonstrated.
Several studies have used clinical and pathologic features to attempt to define patients at low risk for IBE (defined in the current work as the local recurrence of DCIS or invasive carcinoma in the same breast) following surgical excision without radiation, noted radiation oncologist Lawrence J. Solin, MD, of the Albert Einstein Medical Center in Philadelphia, Pennsylvania, and colleagues in Journal of the National Cancer Institute.
Although adding radiation therapy after surgical excision of DCIS reduces the risk of local recurrence and invasive local recurrence by approximately 50%, most patients will not develop local recurrence if they have surgery without radiation, and many do undergo surgery alone.However, reproducible and reliable methods using clinical and pathologic factors to select patients for surgical excision alone have not been established.
Solin’s group analyzed tissue from 327 participants of the Eastern Cooperative Oncology Group (ECOG) E5194 study. That nonradomized, multicenter trial evaluated treatment using surgical excision without radiation for selected women with DCIS.
Solin and fellow investigators chose ECOG E5194 as an independent study to validate the “DCIS score” yielded by their own work, in which they employed the 12-gene Oncotype DX breast cancer assay. The DCIS score was calculated from seven cancer-related genes and five reference genes. The researchers then studied the association between the prospectively defined DCIS score and the risk of developing an IBE.
The continuous DCIS score was found to be statistically significantly associated with the risk of developing an IBE when adjusted for tamoxifen use, and with invasive IBE. The 10-year risk of developing an IBE was 10.6% in the group prespecified as low-risk, 26.7% in the group prespecified as intermediate-risk, and 25.9% in the group prespecified as high-risk. The 10-year risks for developing an invasive IBE were 3.7%, 12.3%, and 19.2%, respectively.
DCIS score, tumor size, and menopausal status were all associated with IBE risk.
“The DCIS score quantifies IBE risk and invasive IBE risk, complements traditional clinical and pathologic factors, and provides a new clinical tool to improve selecting individualized treatment for women with DCIS who meet the ECOG E5194 criteria,” concluded Solin and associates.