Demystifying DCIS Breast Cancer

Test seeks to predict prognosis and guide treatment decisions.
By Kari Bohlke, ScD

Ductal carcinoma in situ (DCIS) of the breast is a commonly diagnosed, very early stage of breast cancer. As research on DCIS has increased, it has become apparent that the underlying biology of DCIS can vary substantially among patients. Researchers in the field of genomics are working on characterizing this variability, with the goal of providing more-personalized treatment.

First, a little background: DCIS refers to abnormal cells in the lining of a breast duct. It is classified as Stage 0 breast cancer—the earliest possible stage. The condition usually does not produce any symptoms (such as a breast lump), and it was an uncommon diagnosis prior to the introduction of screening mammography. Diagnoses increased greatly once mammography became widespread, and DCIS now accounts for up to one-quarter of all breast cancer diagnoses in the United States.1

Treatment of DCIS generally involves either a lumpectomy (removal of the abnormal area of the breast) or a mastectomy (removal of the entire breast). When DCIS is treated with lumpectomy, additional treatment with radiation therapy can reduce the risk of cancer recurrence.2 The benefits provided by radiation therapy, however, may vary depending on the underlying biology of the DCIS. Radiation therapy may be particularly important for women with DCIS that has a higher likelihood of recurring after surgery. The challenge, of course, is predicting the risk of recurrence prior to making treatment decisions. Current classification systems for DCIS have some limitations.

This is where genomics enters the picture. The term genomics generally refers to the study of the entire genome (all of the DNA in an organism). Genomics can consider multiple genes and how they interact with one another and the environment to affect health.

What Is Oncotype DX?

Oncotype DX is the first clinically validated commercial genomic assay for patients with DCIS. Oncotype DX reveals the underlying biology that can help guide DCIS treatment decisions by predicting the risk of any local recurrence of breast cancer (DCIS or invasive) and the risk of local invasive carcinoma and allowing for personalized treatment based on tumor biology as determined by the DCIS recurrence score.

Examples of genomic tests are the Oncotype DX breast and colon cancer tests. The tests evaluate the activity of several genes in a sample of tumor tissue to assess the likelihood of cancer recurrence. Information about recurrence risk obtained using the Oncotype DX genomics test can be used to individualize treatment decisions.

The Oncotype DX breast cancer test was originally developed for use in certain groups of women with early-stage, invasive breast cancer, but it’s now possible to also use the test to generate a DCIS recurrence score—an indicator of the likelihood that DCIS will recur after treatment with lumpectomy alone.

Results from a study of the DCIS score were recently presented at the 34th Annual CTRC-AACR San Antonio Breast Cancer Symposium.3 The study involved 327 women with DCIS who had participated in an earlier clinical trial of DCIS treatment. The women had been treated with lumpectomy but had not received radiation therapy.

Three-quarters of the patients had a low risk of recurrence based on the DCIS score. For these women the likelihood of any kind of local recurrence (either DCIS or invasive breast cancer) was 12 percent, and likelihood of a recurrence that involved invasive breast cancer was 5 percent. By comparison, among women with a high risk of recurrence based on the DCIS score, the likelihood of any kind of local recurrence was 27 percent, and the likelihood of a recurrence that involved invasive breast cancer was 19 percent.

These results suggest that the Oncotype DX DCIS score provides information about the risk of recurrence after breast-conserving surgery for DCIS. This information could help guide decisions about the need for postoperative radiation therapy following treatment with lumpectomy. Research in genomics is expanding at a rapid rate and will have a profound effect on many aspects of disease prevention, diagnosis, and treatment. Diseases such as cancer are remarkably complex; genomics provides researchers and physicians with tools to explore and address these complexities and help individualize treatment decisions.

References

1. Kerlikowske K. Epidemiology of ductal carcinoma in situ. Journal of the National Cancer Institute Monographs. 2010;41:139-41.

2. Goodwin A, Parker S, Ghersi D, Wilcken N. Post-operative radiotherapy for ductal carcinoma in situ of the breast. Cochrane Database of Systematic Reviews. 2009;4:CD000563.

3. Solin LJ, Gray R, Baehner FL et al. A quantitative multigene RT-PCR assay for predicting recurrence risk after surgical excision alone without irradiation for ductal carcinoma in situ (DCIS): a prospective validation study of the DCIS Score from ECOG E5194. Paper presented at: 34th Annual CTRC-AACR San Antonio Breast Cancer Symposium. December 6-10, 2011; San Antonio, TX. Abstract S4-6.