Trends and predictors of size and grade for ductal carcinoma in situ (DCIS) in BreastScreen Victoria

Previous studies have examined predictors, such as hormone replacement therapy (HRT) use, of size and grade of invasive breast cancer, but little is known about factors that influence prognostic features of DCIS. We evaluated factors associated with size and grade of DCIS in a large screening programme, BreastScreen Victoria.

A total of 1127 women were diagnosed with DCIS and 5301 with invasive breast cancer in BreastScreen Victoria between 1993 and 2000. We used multiple linear regression to evaluate predictors of size and multinomial logistic regression to evaluate predictors of grade.

The ratio of DCIS to invasive tumours decreased with age but did not differ by time since the last screen. Older age (over 70 years) was associated with smaller DCIS size and better differentiated tumours (P = 0.05) compared with women aged 50–69 years. A longer screening interval was associated with larger DCIS tumours (P = 0.01) but was not associated with grade of DCIS. There was a borderline significant association between current HRT use and decreased risk of high-grade DCIS lesions (P = 0.07) in univariate analyses, but this disappeared after adjustment for size and histology.

There are important differences between predictors of DCIS and invasive cancer. In contrast to invasive cancer, HRT is not associated with size or grade of DCIS.