Ductal carcinoma in situ detected in the mammographic era: an analysis of clinical, pathologic, and treatment-related factors affecting outcome with breast-conserving therapy.

PURPOSE: We reviewed our institution's experience treating predominantly mammographically detected ductal carcinoma in situ (DCIS) with breast-conserving therapy (BCT) to determine if any clinical, pathologic, or treatment-related factors affected outcome.

METHODS AND MATERIALS: From January 2, 1980 to January 6, 1992, 107 breasts in 105 patients were treated with BCT at William Beaumont Hospital, Royal Oak, MI. All patients underwent at least an excisional biopsy and 70 patients (65%) were reexcised. All patients received whole-breast irradiation to a median dose of 50.4 Gy (range 43.1 to 56.0 Gy). Ninety-nine patients (93%) received a supplemental boost to the tumor bed for a median total dose of 60.4 Gy (range 59.1 to 71.8 Gy) using either photons (2 patients), electrons (69 patients), or an interstitial implant (28 patients).

RESULTS: With a median follow-up of 78 months, 10 patients have failed in the treated breast for a 5- and 10-year actuarial local control rate of 91.2 and 89.8%, respectively. Thirteen percent of the population have been followed for 10 years or more. Three recurrences were pure DCIS, and seven were invasive. All patients were salvaged with mastectomy. Nine patients remain without evidence of disease a median of 30.6 months after surgery. One patient failed distantly 36 months after local recurrence for an ultimate cause specific survival of 99%. Potential clinical (age, mammographic findings, method of detection, etc.), pathologic (nuclear grade, margins, etc.), and treatment-related factors (dose, boost technique, reexcision status, etc.) affecting outcome were analyzed. No variable was found to be associated with an ipsilateral breast tumor recurrence. However, when only recurrences that occurred within or immediately adjacent to the lumpectomy cavity were analyzed, both margin status and the extent of cancerization of lobules (COL) near the surgical margin were associated with the development of a local recurrence.

CONCLUSIONS: Patients treated with BCT for predominantly mammographically detected DCIS achieve excellent rates of local control and overall survival. Both margin status and the extent of COL near the surgical margin appear to be associated with recurrences within or immediately adjacent to the lumpectomy cavity. These data suggest that careful attention to the completeness of surgical resection of DCIS is an important determinant of outcome.