Overtreatment of Early Lesions
New technologies do not merely detect breast cancer earlier, but they can also complicate the screening and treatment processes. Improvements in the sensitivity of breast imaging techniques have led to an increase in the identification of small abnormalities whose biology is not well understood. For example, many consider ductal carcinoma in situ (DCIS) to be a premalignancy because it appears cancerous but has not invaded surrounding tissues or metastasized.
The number of women diagnosed with DCIS has greatly increased since screening mammography was widely adopted. Between 1973 and 1983, DCIS accounted for only 0.3 to 5.2 percent of all cases of breast cancer diagnosed, depending on the age group. In contrast, between 1983 and 1992, DCIS constituted 12 to 18 percent of all newly diagnosed cases of breast cancer and may account for as much as 30 percent of breast cancer cases identified by screening mammography (Ernster et al., 1996).
Among women ages 40 to 49, as many as 40 percent of all cases of breast cancer detected by mammography are DCIS (Ernster and Barclay, 1997).
Although some DCIS lesions will develop into invasive cancers, there is no method for determination of whether a particular DCIS will develop into a life-threatening metastatic cancer. In fact, one study reported finding occult DCIS at autopsy in 40 percent of women between 40 and 50 years of age who died from other causes (Nielsen et al., 1987), although the incidence in other similar studies (6 to 18 percent) has not been quite so high (see Welch and Black  and references therein).
Initially, DCIS was often treated by mastectomy, but more recently, lumpectomy (removal of tissue surrounding the lesion) followed by radiation has become more common, as it has with invasive breast cancer.
However, the pattern of treatment varies greatly, and because the rate of DCIS detection has increased, thousands of mastectomies for DCIS are still performed each year (Ernster et al., 1996). In some cases, the treatment decision may be due to a patient’s inaccessibility to facilities that provide radiation therapy (e.g., because of where a woman lives or because she lacks medical insurance).
Another type of noninvasive high-risk breast lesion, referred to as “lobular carcinoma in situ” (LCIS), is as perplexing or even more so than DCIS in terms of biological understanding and clinical management.