Pathologic characteristics of second breast cancers after breast conservation for ductal carcinoma in situ

The number of women diagnosed with ductal carcinoma in situ (DCIS) is increasing. Although many eventually develop a second breast cancer (SBC), little is known about the characteristics of SBCs. The authors described the characteristics of SBC and examined associations between the pathologic features of SBC and index DCIS cases.

Women were identified in the National Comprehensive Cancer Network Outcomes Database who were diagnosed with DCIS from 1997 to 2008 and underwent lumpectomy and who subsequently developed SBC (including DCIS or invasive disease that occurred in the ipsilateral or contralateral breast). The Fisher exact test and the Spearman test were used to examine associations between the pathologic characteristics of SBC and index DCIS cases.

Among 2636 women who underwent lumpectomy for DCIS, 150 (5.7%) experienced an SBC after a median of 55.5 months of follow-up. Of these 150 women, 105 (70%) received adjuvant radiotherapy, and 50 (33.3%) received tamoxifen for their index DCIS. SBCs were ipsilateral in 54.7% of women and invasive in 50.7% of women. Among the index DCIS cases, 60.6% were estrogen receptor (ER)-positive, and 54% were high grade, whereas 77.5% of SBCs were ER-positive, and 48.2% were high grade. Tumor grade (P = .003) and ER status (P = .02) were associated significantly between index DCIS and SBC, whereas tumor size was not (P = .87).

After breast conservation for DCIS, SBC in either breast exhibited pathologic characteristics similar to the index DCIS, suggesting that women with DCIS may be at risk for developing subsequent breast cancers of a similar phenotype.