Jacky Luiten

Trends in incidence and tumor grade in screen‐detected DCIS and invasive breast cancer | 19 2 combination with calcifications, architectural distortion, asymmetry or other abnormality. In our screening region, screen‐film mammography screening was gradually replaced by digital mammography screening between May 2009 and April 2010. Follow‐up procedure All women with suspicious mammographic findings at screening were recalled to their general practitioner and subsequently to a breast unit of a regional hospital for further analysis which consisted of physical examination by a surgical oncologist and additional radiological breast examinations. Subsequent biopsy procedures (including fine needle aspiration cytology, core needle biopsy, vacuum assisted biopsy and/or surgical biopsy) were performed at the discretion of the clinical radiologist and/or surgical oncologist. During 1‐year follow‐up, one of the screening radiologists collected patient characteristics, breast imaging reports, pathology findings, tumor grade [DCIS; low, intermediate, high and invasive carcinoma; B&R grade 1 (low), B&R grade 2 (intermediate) and B&R grade 3 (high)] and surgical reports of all women who were recalled for further analysis of an abnormality detected at screening mammography. Statistical analysis Screened women were grouped into separate cohorts consisting of two years, based on the biennial screening program. The main outcome of this study was the incidence of DCIS and invasive breast cancer which were analyzed separately in each consecutive cohort. Both for DCIS and invasive breast cancer the tumor grade at initial screening and subsequent screening was determined, as well as the proportions and tumor grading of DCIS and invasive breast cancer over time. Statistical analyses were performed using SPSS, version 22.0 (SPSS, Inc., Chicago, USA). The mean differences with standard deviation (SD) were calculated for continuous variables. Trends over time and variations between subgroups were expressed using proportions. Chi‐square analyses were performed to compare proportional differences between categorical groups. P ‐values less than 0.05 were considered statistically significant.