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The management of DCIS requires the coordinated, multidisciplinary interaction of radiologists, surgeons, pathologists, and oncologists. Patients are first assessed to determine if they are candidates for breast-conserving surgery. Women with multicentric DCIS, as defined by the presence of two or more tumors in separate quadrants of the breast, and those with extensive or diffuse DCIS or suspicious-appearing microcalcifications throughout the breast are candidates for mastectomy, as are women in whom negative margins or acceptable cosmesis cannot be achieved with the use of breast-conserving surgery. Some women may prefer mastectomy to breast conservation in order to minimize the chance of ipsilateral recurrence or for other reasons. At present, there is no established role for the use of magnetic resonance imaging in screening patients for DCIS in determining whether breast-conserving surgery is an option.

Patients deemed to be appropriate candidates for breast conservation require complete surgical excision of the affected area. The extent of DCIS in the breast and the existing margin determine the likelihood of identifying residual disease on reexcision. Nearly half of patients with margins that are <1 mm have residual DCIS on re-excision (82). However, the optimal margin width for the management of DCIS is not known. At a minimum, there should be no tumor at the margin.

Neither dissection of axillary lymph nodes nor mapping of sentinel lymph nodes is routinely warranted in patients with DCIS because of the very low incidence of axillary metastases (110). Three to 13% of patients with DCIS, and a slightly greater percentage with DCIS and microinvasion, have isolated tumor cells in sentinel axillary lymph nodes (62). The prognostic significance of these cells is not clear. Clinical experience suggests that patients have a much better outcome than would be predicted by such rates of nodal metastases, and most instances represent micrometastases of unclear metastatic potential. However, sentinel lymph node mapping may be used in selected patients with a higher likelihood of occult invasive cancer—those with extensive, high-grade DCIS or palpable masses—and those undergoing mastectomy as sentinel node mapping cannot be performed afterward if invasive tumor is identified (79).

After breast-conserving surgery, radiotherapy is administered using tangential fields to the whole breast with a standard dose of 45 to 50 Gy delivered in daily fractions of 180 to 200 cGy. On the basis of extrapolation from data on the treatment of invasive breast cancer (11), a radiation boost to the tumor bed may be added to whole-breast treatment, particularly for women with close surgical margins, although the benefit of a boost in the management of DCIS is not established. There is no role for postmastectomy or nodal irradiation in the treatment of DCIS.
It is not yet possible to prospectively identify women who are at sufficiently low risk that radiotherapy may not be of some clinical advantage in preventing recurrences. After discussing the various options, patients may elect not to receive radiation treatment, but they must understand and accept the increased risk of recurrence that this choice probably entails.

In summary, despite considerable advances in our clinical knowledge base, the answer to the question “when should radiotherapy be used for DCIS?” remains complex and surrounded by considerable controversy. Two fundamental considerations must be emphasized:
• A primary goal of breast-conserving therapy for DCIS is to achieve the best possible cosmetic outcome. Attempts to obtain wide surgical margins through deforming, large-volume breast excisions represent cosmetic failures and defeat the purpose of breast conservation.
• Breast irradiation reduces the risk of subsequent invasive or noninvasive carcinoma in the treated breast and thus reduces the risk of the ultimate cosmetic failure— mastectomy.
According to prospectively randomized trials of breast-conserving therapy for DCIS, radiotherapy reduces subsequent breast recurrence in all patient groups irrespective of prognostic risk factors. That is not to say, however, that radiotherapy must be used for all patients with DCIS. In all cases, a realistic and balanced discussion of the relative risks and benefits of treatment options should be presented to the patient. Reasonable estimates of breast recurrence during the ensuing decade with or without radiotherapy are available based on level I evidence from prospective clinical trials. A decision tree to assist in the selection of treatment options is presented in Table 52.5.