Digital Mammography Screening: Does Age Influence the Detection Rates of Low-, Intermediate-, and High-Grade Ductal Carcinoma in Situ?

Purpose: To investigate the association between age at screening and detection rates for ductal carcinoma in situ (DCIS) separately for different nuclear grades after introduction of a population-based digital mammography screening program. Materials and Methods: The retrospective study was approved by the ethics board and did not require informed consent. In 733 905 women aged 50-69 years who participated in a screening program for the first time in 2005-2008 (baseline examinations were performed with digital mammography), DCIS detection rates were determined for 5-year age groups (detection rates per 1000 women screened) to distinguish high-, intermediate-, and low-grade DCIS. Multivariable logistic regression was used to compare detection rates between age groups by adjusting for screening units (P < .05). Results: There were 989 graded DCIS diagnoses among 733 905 women (detection rate, 1.35%): 419 diagnoses of high-grade DCIS (detection rate, 0.57%), 388 diagnoses of intermediate- grade DCIS (detection rate, 0.53%), and 182 diagnoses of low-grade DCIS (detection rate, 0.25%). Detection rate for types of DCIS combined increased significantly across age groups (50-54 years, detection rate of 1.15% [254 of 220985 women]; 55-59 years, detection rate of 1.23% [218 of 177782 women]; 60-64 years, detection rate of 1.34% [201 of 150415 women]; and 65-69 years, detection rate of 1.71% [316 of 184723 women]; P < .001). Of note, the detection rate for high-grade DCIS showed a significant increase with age (odds ratio, 1.18 per 5-year age group; P < .0001). The increase was lower for intermediate-grade DCIS (odds ratio, 1.11; P = .016) and not significant for low-grade DCIS (P = .10). Conclusion: Total DCIS detection rates increase with age, mostly because of an increase in high-and intermediate-grade DCIS, which are precursor lesions that carry a higher risk for transition to more aggressive invasive breast cancer than low-grade DCIS. (C) RSNA, 2015