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Study: Rates of Non-Invasive Breast Cancers Increasing (dateline September 5, 2005)

The incidence of ductal carcinoma in situ (DCIS), a very early form of non-invasive breast cancer, have increased sevenfold since 1980, according to the results of a recent study. At the same time, the number of cases of lobular carcinoma in situ (LCIS), a precancerous condition that increases the risk of breast cancer has also increased. However, invasive DCIS rates have leveled off during this time period, suggesting that the increased use of mammography and improved breast biopsy techniques are contributing to an increase in breast cancer diagnoses.

DCIS is a stage 0 breast cancer, an early form of non-invasive breast cancer. With DCIS, the cancer cells are confined to milk ducts in the breast and have not spread into the fatty breast tissue or to any other part of the body (such as the lymph nodes). DCIS is often first detected by a mammogram. DCIS may appear on a mammogram as tiny specks of calcium (called microcalcifications), generally too small to notice by physical examination. The cure rate for DCIS is close to 100% provided that an accepted standard method of treatment is followed.

Christopher Li, MD., PhD and colleagues at Fred Hutchinson Cancer Research Center have found that in the past two decades, the incidence of DCIS has increased significantly. In their study, the researchers analyzed data from nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results, or SEER, Program, which is funded by the National Cancer Institute. They found that DCIS incidence rates increased 7.2-fold from 1980 to 2001, 1.8-fold over the past 10 years (1992-2001), and 1.1-fold over the past 5 years (1997-2001). DCIS cases were highest among women over 50 years of age.

While non-invasive DCIS increased the most during the period studied, Dr. Li and his team found that cases of an invasive form of DCIS leveled off or decreased. Comedo type DCIS (also referred to as Comedocarcinoma) is an invasive form of breast cancer that tends to be more aggressive than the non-comedo types of DCIS. Pathologists are able to easily distinguish between comedo type DCIS and other non-comedo types when examining the cells under a microscope because comedo type DCIS tends to plug the center of the breast ducts with necrosis (dead cells). When necrosis is associated with cancer, it often means that the cancer is able to grow quickly.

The researchers also found that, for the same period, the incidence of LCIS, a precancerous condition, also increased. Specifically, LCIS incidence rates increased 2.6-fold (from 1980 to 2001, 1.3-fold over the past 10 years, and 1.1-fold over the past 5 years. Though categorized as a stage 0 breast cancer (the earliest stage), LCIS is not considered a cancer. Rather, it is "marker" (a signal) that breast cancer may develop. According to the National Cancer Institute, a woman with LCIS has a 25% chance of developing some form of invasive cancer (either lobular, or more commonly, infiltrating ductal carcinoma) within her lifetime.

Experts believe that the higher rates of DCIS and LCIS may not be caused by a true increase in the rate of early-stage breast cancer. Rather, the increased may be caused by more rigorous breast cancer screening and advances in mammography techniques. Often, LCIS is encountered serendipitously (by chance) while a pathologist is examining tissue from a breast biopsy that was performed for another reason (for example, to examine an area of concern found by physical examination or with mammography).

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