Abstract P5-17-06: Prognostic value of method of detection in primary pure DCIS
Authors: Elshof LE , Schaapveld M , Schmidt MK , van Leeuwen FE , Rutgers EJTh , Wesseling J 
Published: May 2016

Abstract
Background
Population-based mammographic screening programs have led to a substantial increase in incidence of ductal carcinoma in situ (DCIS). We assessed whether the method of detection provides prognostic information among women with DCIS detected through the Dutch screening program (screen-detected DCIS) and those with DCIS not detected within the national screening program (non-screen-detected DCIS). This could have impact on the treatment strategy of screen-detected DCIS as compared to symptomatic DCIS.
Methods
We studied a population-based retrospective cohort comprising 7,106 women aged 49-76 years with primary pure DCIS, who were treated by mastectomy or breast conserving surgery with or without radiotherapy between 1989 and 2004 in the Netherlands. Risk of subsequent ipsilateral and contralateral invasive breast cancer and overall survival among women with screen-detected (n=4,905) and non-screen-detected (n=2,201) DCIS were compared using Cox regression, adjusting for treatment (time-dependent), age (time-scale), diagnosis period and follow-up duration. Because of gradual implementation of the screening program in the Netherlands, we defined two periods based on year of DCIS diagnosis: 1989-1998 (gradual implementation of screening) and 1999-2004 (full coverage of screening).
Results
With a median follow-up of 10.5 years (interquartile range 7.7-14.0 years) 366 ipsilateral (screen-detected DCIS n=234, non-screen-detected DCIS n=132) and 380 contralateral (screen-detected DCIS n=245, non-screen-detected DCIS n=135) invasive breast cancers were diagnosed, and 1,088 of 7,106 women died (screen-detected DCIS n=603, non-screen-detected DCIS n=485). From 1989 to 2004 the number of non-screen-detected DCIS remained stable (mean 140, range 110-187 per year), whereas the number of screen-detected primary pure DCIS increased from 8 in 1989 to 596 in 2004. Ipsilateral invasive breast cancer risk was lower for screen-detected DCIS compared to DCIS not detected within the national screening program, irrespective of DCIS treatment, period of diagnosis, and follow-up duration (adjusted hazard ratio [HR] 0.74, 95% confidence interval [CI] 0.59-0.92, p &lt; 0.01). The prognostic value of method of detection was similar across categories of treatment, period of diagnosis, and follow-up duration. The risk of contralateral invasive breast cancer did not differ between screen-detected DCIS and non-screen-detected DCIS (adjusted HR 0.89, 95% CI 0.71-1.11, p = 0.3) and neither did all-cause mortality (adjusted HR 0.91, 95% CI 0.79-1.04, p = 0.2).
Conclusion
Women with primary pure DCIS detected through the Dutch screening program had lower risk of subsequent ipsilateral invasive breast cancer, irrespective of DCIS treatment, compared to women whose DCIS was not detected within the national screening program. However, the magnitude of this risk difference does not warrant a different treatment strategy of screen-detected DCIS as compared to non-screen-detected DCIS. Having a screen-detected DCIS was not associated with risk of subsequent contralateral invasive breast cancer and all-cause mortality.
Citation Format: Elshof LE, Schaapveld M, Schmidt MK, van Leeuwen FE, Rutgers EJTh, Wesseling J. Prognostic value of method of detection in primary pure DCIS. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-17-06.