TREATMENT FOR DUCTAL CARCINOMA IN SITU IN AN ASIAN POPULATION: OUTCOME AND PROGNOSTIC FACTORS

Abstract

Breast cancer is the most common cancer among Singapore women and ductal carcinoma in situ (DCIS) is believed to be the precursor of most invasive breast cancers. The incidence of DCIS has increased dramatically with mammographic screening, but its treatment remains controversial. Further, results of treatment for DCIS in Asians, and in particular Singapore women, are lacking. We review our institution's results treating a predominantly Chinese population with DCIS of the breast before the introduction of mammographic screening and aim to determine treatment outcomes and identify prognostic factors for disease recurrence. Between January 1994 and December 2000, 170 consecutive patients with DCIS were treated at our institution. One hundred and three (60.5%) were managed with breast conservation (17 with local wide excision alone and 86 with adjuvant irradiation following wide excision) whereas 67 (39.4%) underwent mastectomy. Of those who underwent wide local excision, 56 (54.3%) underwent re-excision for margin clearance. Overall, the axilla was surgically staged in 47 (27.6%) and no nodal involvement was found in all cases. Pathological specimens were reviewed by one of the authors. Median follow up was 86 months (range 4-151 months). Sixty-two patients (36%) were asymptomatic at presentation whereas most (64%) presented with clinical symptoms; out of these more than half (54%) presented with a palpable lump. The median size of tumours was 13 mm (range 1.5-90 mm). Patients who underwent breast conservation surgery had oncologically more favourable lesions - with a significantly higher incidence of smaller and non-palpable lesions and lesions of lower nuclear grade. However, there was also a significantly higher incidence of local recurrence in this group. At the end of follow up, there were 12 patients (7.1%) who developed local recurrence and 8 patients (4.7%) developed contralateral disease. The crude incidence of all breast events (including both local failure and contralateral events) at 5 years was 5.6%. Median time to the development of any breast event (local recurrence or contralateral disease) was 60 months (range 12-120 months). The cumulative 5-year recurrence-free survival for patients who underwent breast conservation surgery was 94%. Factors influencing local recurrence rate were close or involved margins (<or=1 mm) and lack of adjuvant radiotherapy. There were no cancer-specific deaths during the period of follow up. Our results indicate that rates of cancer-specific survival were similar after mastectomy and breast conserving surgery. However, a close or involved margin (<or=1mm) and lack of adjuvant radiotherapy were associated with local recurrence, with margin status being the independent predictor for local recurrence. Our results reinforce that optimizing local therapy is crucial to improve local control rates in women treated with DCIS in our population.