Resection margin status is one of the most significant factors for local recurrence in patients with ductal carcinoma in situ (DCIS) treated with breast-conserving surgery with or without radiation. However, its impact on chest wall recurrence in patients treated with mastectomy is unknown. The purpose of this study was to determine chest wall recurrence rates in women with DCIS and close (<5 mm) or positive mastectomy margins in order to evaluate the potential role of radiation therapy.

Between 1985 and 2005, 193 women underwent mastectomy for DCIS. Fifty-five patients had a close final margin, and 4 patients had a positive final margin. Axillary surgery was performed in 17 patients. Median follow-up was 8 years. Formal pathology review was conducted to measure and verify margin status. Nuclear grade, architectural pattern, and presence or absence of necrosis was recorded.

Median pathologic size of the DCIS in the mastectomy specimen was 4.5 cm. Twenty-two patients had DCIS of >5 cm or diffuse disease. Median width of the close final margin was 2 mm. Nineteen patients had margins of <1 mm. One of these 59 patients experienced a chest wall recurrence with regional adenopathy, followed by distant metastases 2 years following skin-sparing mastectomy. The DCIS was high-grade, 4 cm, with a 5-mm deep margin. A second patient developed an invasive cancer in the chest wall 20 years after her mastectomy for DCIS. This cancer was considered a new primary site arising in residual breast tissue.

The risk of chest wall recurrence in this series of patients is 1.7% for all patients and 3.3% for high-grade DCIS. One out of 20 (5%) patients undergoing skin sparing or total skin-sparing mastectomy experienced a chest wall recurrence. This risk of a chest wall recurrence appears sufficiently low not to warrant a recommendation for postmastectomy radiation therapy for patients with margins of <5 mm. There were too few patients with positive margins to draw any firm conclusions.