New Tool for DCIS Breast Cancer Identifies Lower-Risk Patients Who Can Avoid Radiation

Ductal Carcinoma In Situ (DCIS) is an early or pre-invasive form of breast cancer that poses challenging decisions for patients and physicians in determining how to best treat the disease.  Unlike invasive breast cancer, the tumor cells in DCIS are confined to the milk ducts within the breast.

Breast-conserving surgery (usually lumpectomy), rather than mastectomy, has become the most common surgical procedure for DCIS.  After breast-conserving surgery for DCIS, local recurrences of DCIS or a new invasive breast cancer occur, on average, in 20-25 percent of patients at 10 years, who had surgery alone and no other treatments.  However, the vast majority (65-70 percent) of DCIS patients go on to receive radiation.  While the addition of radiation therapy for DCIS has been shown in clinical trials to reduce local recurrence risk, it has not been shown to prolong survival in DCIS patients (in invasive breast cancer, the addition of radiation significantly improves rates of distant metastases and survival between treated and untreated patients).  ¹Similar to chemotherapy, radiation has significant side effects and to date, there have been no clinically validated molecular markers that clearly identify which patients might be low-risk and avoid radiation and which patients might be high-risk, for whom the side effects of radiation might be obtaining a reduction in local recurrence risk.

Because of the unique challenges presented by a DCIS diagnosis, with strong encouragement from breast cancer advocates and physicians, we at Genomic Health began research to better understand the biology of DCIS so we could develop a tool to help physicians and patients make more informed, individualized treatment decisions for DCIS based on each patient’s individual cancer biology.  The Oncotype DX breast cancer assay we developed for invasive breast cancer has been available since 2004, and is used to predict the likelihood of chemotherapy benefit as well as recurrence in stage I and I invasive breast cancer to help optimize treatment options.

Applying our learnings from the validation of Oncotype DX in invasive breast cancer, we partnered with the Eastern Cooperative Oncology Group (ECOG) to conduct a large, prospectively designed clinical validation study to determine if Oncotype DX could predict local recurrence in patients with DCIS breast cancer. We were pleased to share the positive results at this year’s San Antonio Breast Cancer Symposium, which showed that, for the first time, a multi-gene test (the Oncotype DX DCIS score) can be used to identify approximately 75 percent of patients with lower risk DCIS that may be treated without radiation.

The study analyzed 327 DCIS tumor specimens from patients previously enrolled in the E5194 study of breast-conserving surgery alone.  The Oncotype DX breast cancer test was performed on each specimen, using a pre-specified DCIS algorithm to predict local recurrence regardless of whether adjuvant tamoxifen was given.

The study demonstrated that 75% of patients have a low DCIS Score as pre-specified in the study and may be able to forego radiation therapy.  DCIS breast cancer patients with a low DCIS Score had a low 12% likelihood of a local recurrence, defined as either the development of a new invasive breast cancer or the recurrence of DCIS in the same breast, and an even lower 5% likelihood of developing a new invasive breast cancer.  Conversely, the study demonstrated that patients with high DCIS Score had a 27% likelihood of local recurrence, of which approximately half was likely to develop a new invasive breast cancer.

The study met its primary endpoint by demonstrating that a pre-specified Oncotype DX DCIS Score goes beyond traditional clinical and pathologic measures, such as tumor size, tumor grade, and patient age, to predict the risk of local recurrence, defined as either the development of a new invasive breast cancer or the recurrence of DCIS in the same breast.

Based on these results, we plan to make the Oncotype DX DCIS Score available to physicians and their DCIS patients on December 28, 2011.  By revealing the underlying biology of DCIS, we can now help quantify the likelihood of local recurrence, which is key to devising an individualized treatment plan which will provide excellent outcomes for patients with the least treatment, toxicity, and disruption of daily life.

For more information about Oncotype DX go to www.mybreastcancertreatment.org or call 1-866-662-6897.