Ductal Carcinoma in Situ (DCIS)

Years ago DCIS represented less than 5% of all breast cancers diagnosed. With the advent of routine screening mammography in the United States, the incidence of DCIS has risen to over 20% of all breast cancers. The typical patient is asymptomatic and has undergone screening mammography that has identified suspicious calcifications. These pleomorphic, linear, and branching calcifications represent intraductal calcium deposits at areas of rapid cell turnover and necrosis.

Treatment options offered to women with this diagnosis include total mastectomy and lumpectomy with radiation. Lymph node sampling (sentinel node biopsy) is not routinely performed unless the area involved is considered large enough to hide an invasive cancer.

DCIS is truly a preinvasive lesion, meaning that complete removal will prevent an invasive malignancy from developing at that site. Local therapy, therefore, is the key to cure in these patients (see the description of the NSABP B-17 trial below).

In addition, the fact that a woman develops DCIS in one area of the breast indicates that she is at risk for subsequent development of breast cancer in other areas of that same breast, as well as on the contralateral side. For this reason, most patients are offered preventive therapy with tamoxifen or an aromatase inhibitor after surgical/radiation treatment has been completed.

Evidence-Based Surgery: NSABP B-17 Trial

The National Surgical Adjuvant Breast and Bowel Project B17 (NSABP B17) trial¹ randomized women with DCIS to treatment with mastectomy, lumpectomy, or lumpectomy followed by radiation therapy. The first hypothesis was that overall survival would be no different when patients were treated with mastectomy or lumpectomy. The second hypothesis was that local recurrence would be reduced when radiation was added to lumpectomy, and would be equal to mastectomy. Over 800 women were enrolled and randomized. The results were first presented with 5 years of follow-up. The first hypothesis was proven: there was no difference in survival regardless of treatment modality. The second hypothesis was also proven: lumpectomy alone for DCIS led to a 24% local recurrence rate, while radiation reduced the recurrence rate to an acceptable 8%. In addition, subsequent recurrences were less likely to be invasive cancers in the women who had received radiation therapy. This trial is the justification for our current management of DCIS. Adjuvant radiation therapy is an essential component of breast conservation.