Ductal carcinoma in situ, which accounts for 30% of all newly diagnosed breast cancers, does not always evolve into a lesion with metastatic potential. Only a proportion of these cases will progress to invasive breast cancer, but up until recently, it has not been possible to identify reliably which patients require adjuvant radiation to prevent tumor recurrence in the breast following surgical excision.

The Oncotype DX Ductal Carcinoma in Situ (DCIS) promises to fill that need. Similar to Oncotype DX in the adjuvant setting, Oncotype DX DCIS is a 12-panel gene test with a scoring system that categorizes cancers as low, intermediate, or high risk for local tumor recurrence over 10 years following treatment with breast-conserving surgery alone. A large population-based study presented at the 2014 San Antonio Breast Cancer Symposium validated the Oncotype DX DCIS in a diverse population of women with ductal carcinoma in situ.¹

The current study is important, because the E5194 study that showed Oncotype DX DCIS was predictive of local tumor recurrence was based on a select population of women. “Our results confirm the E5194 results in a more diverse population,” explained lead author Eileen Rakovitch, MD, of Sunnybrook Health Sciences Centre, University of Toronto, Canada.

“This is the first multigene biomarker assay to provide individualized estimates of the risk of local tumor recurrence in women treated by breast conservation alone. The DCIS Score can be used for discussions between patients and physicians to decide upon a course of further treatment. It is hoped that this will improve individualized management of ductal carcinoma in situ and reduce overtreatment of women at low risk of recurrence and undertreatment of women at higher risk of recurrence,” Dr. Rakovitch stated.

The Oncotype DX DCIS is expressed in variables from 0 to 100. A DCIS Score of less than 39 indicates a low risk for tumor recurrence, a DCIS Score of 39 to 54 indicates an intermediate risk for tumor recurrence, and a DCIS Score of 55 or higher indicates a high risk for tumor recurrence.

Predicting Tumor Recurrence

A population-based study was undertaken to validate the score in women diagnosed with pure ductal carcinoma in situ and treated with breast-conserving surgery alone in Ontario, Canada. Of 1,658 cases that met these criteria, tissue blocks were available for 858, and 257 were excluded, leaving a study cohort of 571 individuals. At a median follow-up of 9.6 years, 101 cases of local tumor recurrence were identified (57, invasive; 44, ductal carcinoma in situ).

When the DCIS Score was used retrospectively, the 10-year risk of local tumor recurrence was estimated at 13% for low-risk patients, 28% for intermediate-risk patients, and 33% for high-risk patients. The DCIS Score also predicted invasive tumor recurrence and ductal carcinoma in situ recurrence, she said.

“Comparing the Ontario cohort with the more highly selected E5194 cohort, outcomes were remarkably similar,” Dr. Rakovitch said. “The Oncotype DX DCIS improves risk stratification and provides individualized estimates of risk, which will help clinicians and patients better understand the risk of tumor recurrence, and individuals can weigh their own risk in making treatment decisions.” ■

Disclosure: Dr. Rakovitch is the principal investigator for this study, and her institution received research funding from Genomic Health Inc.

Reference

1. Rakovitch E, Nofech-Mozes S, Hanna W, et al: A large prospectively designed study of the DCIS score: Predicting recurrence risk after local excision for ductal carcinoma in situ patients with and without irradiation. 2014 San Antonio Breast Cancer Symposium. Abstract S5-04. Presented December 12, 2014.