Ductal carcinoma in situ. Part 2: Treatment.

Several dilemmas exist when treating a patient with ductal carcinoma in situ (DCIS): the high rate of inter-observer variation for pathologists who must diagnose these tumours; the potential for over- and under-treatment; and the uncertainty about the best way to inform a patient who must often make a decision between breast conservation and mastectomy. Mastectomy is nearly 100% curative, is expedient, but may represent over-treatment for many women, particularly those with asymptomatic mammographically detected lesions. Axillary dissection is not recommended as a routine except for patients with lesions over 5 cm in whom the risk of micro-invasion and lymph node involvement increases. Conservative surgery (CS) alone is associated with a local recurrence rate of approximately 20%, and half of these recurrences (10% overall) are invasive, with a potential long-term cure rate of at least 90%. The addition of radiation to CS reduces the risk of local recurrence to approximately 10%, half of these recurrences (5%) are invasive for a potential long-term cure rate of 95%. Several randomized trials comparing CS with or without radiation therapy (RT) are in progress. The factors that increase the rate of local recurrence after CS alone for DCIS include close or involved margins, and the presence of necrosis or high-grade tumours. Patients with these features should have radiation therapy if breast conservation is preferred. Patients with low-grade tumours (without necrosis) up to 15 mm, with clear margins of at least 10 mm, who agree to be closely observed may be good candidates for CS alone. A critical review of the literature is presented.