ASPO Abstracts
Long term outcomes of ductal carcinoma in situ (DCIS) of the breast in a population-based cohort
Category: Survivorship & Health Outcomes/Comparative Effectiveness Research, Pre-Malignant Conditions
Conference Year: 2018
Abstract Body:
Approximately 25% of breast cancers detected by screening mammography are ductal carcinoma in situ (DCIS), a noninvasive form of breast cancer. Uncertainty regarding whether all DCIS has malignant potential has generated concern about overtreatment. With limited data on outcomes of untreated DCIS, information on long term outcomes after treated DCIS is useful to identify patient subgroups that may be appropriate for trials of active surveillance or other novel management strategies. We identified 1488 women diagnosed with primary DCIS in Vermont during 1993-2012. Medical records data were prospectively obtained by the Vermont Breast Cancer Surveillance System, which includes a registry of breast imaging performed at radiology facilities in Vermont, a statewide breast pathology database, and linkage to the Vermont Cancer Registry (VCR). A centralized review of available archived tumor specimens (N=1108) permitted confirmation of DCIS in 1070 cases (96.6%). Follow-up for long term outcomes was achieved through monitoring of radiology, pathology, and VCR records. During 11,112 person-years of follow-up (median 7.7 years), 206 cases experienced a second breast cancer diagnosis (1.9 per 100 person-years). The rate of second events was 2.5 per 100 person-years (95%CI:2.0,3.1) among cases diagnosed during 1993-1999 and declined to 1.4 per 100 person-years (95%CI:0.8,2.1) among cases diagnosed during 2009-2012. This decline was attributable to temporal changes in adjuvant treatment. In multivariable- adjusted models, risk of a second event was reduced by 32% among women treated with breast conserving surgery (BCS) and radiation (HR=0.68; 95%CI:0.48,0.96) and by 62% among women treated with BCS, radiation, and endocrine therapy (HR=0.38; 95% CI:0.24,0.60), in comparison to women treated with BCS only. Radiation therapy reduced the risk of an ipsilateral event (HR=0.49; 95%CI:0.33,0.72), whereas endocrine therapy reduced the risk of both ipsilateral (HR=0.47, 95%CI:0.29,0.74) and contralateral (HR=0.42; 95%CI:0.22,0.82) events. Risk reducing treatment effects were similar for both DCIS and invasive second events. Future analyses will evaluate patient factors, tumor characteristics, and tumor/stromal molecular markers in relation to long term outcomes.
Keywords: ductal carcinoma in situ, DCIS, breast cancer, epidemiology, recurrence