Digital mammography screening: association between detection rate and nuclear grade of ductal carcinoma in situ.

PURPOSE

To determine the relationship between overall detection rates of ductal carcinoma in situ (DCIS) and the specific detection rates of low-, intermediate-, and high-grade DCIS at the start of a digital mammography screening program.

MATERIALS AND METHODS

The study was approved by the local ethics board and did not require informed consent. Data were included of the first round of digital mammography examinations, performed in 17 screening units in women aged 50-69 years from 2005 to 2008. Grading was provided by the cancer registry for 1018 DCIS cases. The association between the overall cancer detection rate (cases per 100 women screened) and the separate cancer detection rate for invasive cancers and for DCIS was assessed. Likewise, the total DCIS cancer detection rate was separated into rates for low, intermediate, and high grades. Spearman rank correlations were used for analysis.

RESULTS

The overall cancer detection rate correlated with both the cancer detection rate of invasive cancers and the cancer detection rate of DCIS (r = 0.96 and r = 0.88, respectively; P < .001 for both). The cancer detection rate of total DCIS with grading varied among screening units (range, 0.05-0.25), it was borderline not significantly correlated with the cancer detection rate of low-grade DCIS (range, 0.004-0.05; r = 0.49; P = .052), and it showed significant correlations with higher cancer detection rate of intermediate-grade DCIS (range, 0.02-0.12; r = 0.89; P < .001) and of high-grade DCIS (range, 0.03-0.11; r = 0.88; P < .001).

CONCLUSION

This study demonstrates that high overall cancer detection rates in digital mammography screening are related to high detection rates of invasive cancers, as well as DCIS. Increases in the detection rates of DCIS were not driven by disproportionate increments of the slowly progressive low-grade subtype but rather by increased rates of intermediate- and high-grade subtypes that carry a higher risk of transition to invasive cancers.