Ductal Carcinoma In Situ (DCIS) is a non-invasive cancer in the end ducts of the breast. Each year 64,000 American women are diagnosed with DCIS, amounting to 30 percent of women diagnosed with breast cancer. Almost always it shows up as tiny calcium spots on a mammogram in women with no lumps and no symptoms. It is not an immediately life-threatening cancer, and some experts question whether it should be called a cancer.
The 10-year overall survival rate is nearly 100 percent, but it is associated with increased risk of invasive breast cancer later on. "Is it possible that some DCIS could be left alone or treated with a chemo preventive agent (one that prevents or delays invasive progression) instead of surgery? Given that the goal of cancer screening is to identify early treatable cancers, it is difficult to propose doing nothing when such cancers are found and difficult to mount clinical trials in which women would forego a known curative treatment." (M.D. Anderson Hospital OncoLog, January 2010;55(1):).
Some DCIS lesions will progress to invasive cancer, and some will remain harmless. Therefore today, doctors prefer to over-treat a woman with DCIS, rather than to do nothing and have the cancer spread. Women with DCIS almost always have surgery because nobody knows which DCIS will spread and which will not. So doctors treat it as if it is an invasive carcinoma by removing the entire breast or breast-conserving lumpectomy with or without radiation therapy.
Women treated with lumpectomy have higher recurrence rates than those treated with mastectomy, and women treated with lumpectomy alone have higher recurrence rates than those who receive lumpectomy with radiation. At present doctors do not recommend radiation treatment following removal of the whole breast, but they often recommend radiation after removing just a lump. Radiation increases risk for heart attacks and heart failure years later on. Some doctors now treat some cases of this condition with "watchful waiting" and close follow up.