Ductal carcinoma in situ (DCIS) is a condition in which abnormal cells are found in the lining of a breast duct. As “in situ” means “in place,” this means the abnormal cells have not spread outside the duct to other tissues in the breast. Also referred to as intraductal carcinoma and stage zero breast cancer, DCIS is the most common noninvasive tumor of the breast.

DCIS is most often discovered during routine mammograms, presenting as very small specks of calcium known as microcalcifications. However, not all microcalcifications indicate the presence of DCIS and the diagnosis must be confirmed by biopsy. Magnetic Resonance Imaging (MRI) has also been used more recently as a diagnostic tool, but questions about the impact of the test on patient outcomes remain. Since the implementation of screening mammography, the rate of new DCIS cases has increased dramatically.

DCIS currently accounts for approximately twenty percent of screening-detected breast cancer, but its true prevalence is challenging to measure because nearly all affected individuals are asymptomatic. By most reports, the risk factors associated with the development of DCIS are similar to those for invasive breast cancer: increased age, family history of breast cancer, previous biopsies, history of hormone replacement therapy, and older age at first childbirth. Tamoxifen, a hormonal drug, has demonstrated a reduction in the incidence of DCIS among high-risk women.

Although the natural course of the disease is not well understood, DCIS can become invasive cancer and spread to other tissues. It is also a marker of increased risk for developing cancer elsewhere in the same or opposite breast. However, not all DCIS will progress to invasive disease, and it is thought that DCIS can be present in some individuals without causing problems over a long period of time. Recent research suggests that DCIS is a spectrum of disease and that certain tumor characteristics may be strong or weak risk factors for subsequent invasive breast cancer. Unfortunately, it is currently not clear which lesion types are more likely to become invasive, leading to difficult treatment decisions for patients and providers.

Because of this uncertainty, DCIS patients are typically treated promptly following diagnosis and have a generally good prognosis. Standard DCIS therapies include breast conservation with or without radiation or mastectomy depending on patient and tumor characteristics. Sentinel lymph node biopsy may also be recommended to high-risk patients, since this is the area where cancer spread is often first detected. Hormone therapy may also be used in effort to prevent DCIS recurrence and to lower the risk of developing estrogen receptor positive breast tumors. However, these drugs’ potential side effects must be weighed carefully.

Since the natural course of DCIS is not well understood and treatment benefit may depend on specific tumor and patient characteristics, the treatment of DCIS remains controversial. To examine these important issues, the National Cancer Institute and Office of Medical Applications of Research of the National Institutes of Health will convene a State-of-the-Science Conference from September 22-24, 2009. The conference will address the following key questions:

What are the incidence and prevalence of DCIS and its specific pathologic subtypes, and how are incidence and prevalence influenced by mode of detection, population characteristics, and other risk factors?
How does the use of MRI or sentinel lymph node biopsy impact important outcomes in patients diagnosed with DCIS?
How do local control and systemic outcomes vary in DCIS based on tumor and patient characteristics?
In patients with DCIS, what is the impact of surgery, radiation, and systemic treatment on outcomes?
What are the most critical research questions for the diagnosis and management of DCIS?

At the conference, invited experts will present information pertinent to these questions, and a systematic literature review prepared under contract with the Agency for Healthcare Research and Quality (AHRQ) will be summarized. Conference attendees will have ample time to ask questions and provide statements during open discussion periods. After weighing the scientific evidence, an unbiased, independent panel will prepare and present a consensus statement addressing the key conference questions.