In the latest Case Record of the Massachusetts General Hospital, a 48-year-old woman presented after routine tomosynthesis had revealed a lesion in the left breast. Core-biopsy and lumpectomy specimens showed ductal carcinoma in situ, with positive margins. Management decisions were made.
In a patient with localized ductal carcinoma in situ (DCIS), the risk of death from breast cancer is low, regardless of the treatment she chooses. Patient preference plays an important role in the choice of therapy, and greater patient involvement in decision making is associated with higher mastectomy rates.
• What is tomosynthesis and how does it compare to mammography?
A tomosynthesis image is composed of a series of 15 low-dose mammographic images obtained at different angles through the breast; the images are then reconstructed into a series of thin slices (at a thickness of 1 mm) in the same plane as the mammographic image. Tomosynthesis, by definition, tackles the problem of overlapping breast tissue that occurs in mammography. As compared with mammography, tomosynthesis has been shown to decrease the false positive rate while increasing the cancer-detection rate.
• What are the treatment options in ductal carcinoma in situ (DCIS) with positive margins after lumpectomy?
Treatment options include mastectomy with or without reconstruction, reexcision and radiotherapy, or reexcision alone. Tamoxifen may be added to any of these treatments. Mastectomy is an extremely effective treatment for DCIS, with local recurrence in 1.4% of patients in a large meta-analysis. The use of skin-sparing mastectomy to facilitate immediate breast reconstruction has not been compared with conventional mastectomy in prospective randomized trials. However, retrospective studies do not suggest an increase in local recurrence rates, and skin-sparing mastectomy is a standard approach in patients undergoing immediate reconstruction. Although mastectomy is an effective method of managing DCIS, it is not necessary for a patient with localized DCIS. Good outcomes have been reported after treatment of localized DCIS with lumpectomy alone or lumpectomy and radiotherapy. The use of radiotherapy reduced the 10-year rate of local recurrence from 28.1% to 12.9% across all ages and tumor grades.
Morning Report Questions
Q: Why is the use of nipple-sparing mastectomy controversial?
A: The use of nipple-sparing mastectomy is more controversial, particularly in patients with DCIS. Occult nipple involvement is reported in up to 58% of patients with breast cancer, and the distance from the primary tumor to the nipple is the best predictor of involvement. Nipple-sparing mastectomy is contraindicated in patients with subareolar or extensive DCIS. In patients with localized DCIS in the periphery of the breast, nipple-sparing mastectomy is an acceptable option.
Q: What is the utility of tamoxifen in the treatment of DCIS?
A: The use of tamoxifen reduces local recurrence by about 5%, but it has not been shown to reduce mortality rates. Among patients with estrogen-receptor-positive tumors, the use of tamoxifen reduced the risk of breast cancer events, although most of the benefit was a reduction in contralateral cancers. The use of tamoxifen reduces the risk of contralateral cancer by approximately 50% and is an alternative to contralateral prophylactic mastectomy.