Roland B Sennerstam
The present study focused on mammography screening during two periods representing 2 years (1991) to 8 years (1997/98) after the introduction of screening in 1989 in the Stockholm Gotland County, Sweden for women aged 50-69 years. Subjects were sorted by age, as younger (<50 years) unscreened women, screening women aged 50-69 years and analyzed in two decades between 50-59 years and 60-69 years respectively, and unscreened women of ≥ 70 years. Tumor size was compared with an unscreened cohort from 1987, 2 years before screening was introduced. Resolution was increased by focusing on three tumor-size intervals instead of mean tumor size, which showed a tending reduction in tumors ≥ 20 mm for women diagnosed with breast cancer aged 50-59 years in the 1991 sample but a significant decline for women aged 60-69 years having attended two screening tests. After 8 years of biennial screening (1997/98) patients with tumor size ≤ 10 mm at diagnosis had significantly increased, and tumors ≥ 20 mm declined significantly–most clearly among 60-69-year-old women after attending up to five screening tests. A transient increase in tumor sized 10 mm to 20 mm was seen due to the stepwise-altered distribution in size. Women in the two unscreened age groups <50 years and ≥ 70 years, were compared with screened women aged 60-69 (1997/98) according to tumor size, genomic instability, proliferation index , lymph node metastases, cyclin-A and ki67, alteration in breast tumor stage I and stage IIB and survival rate. In all parameters except ki67, only in relation to unscreened women <50 years old showed a significant reduction. A post-screening effect was also found for women aged 70-79 years with tumors size > 20 mm still being reduced compared with controls and the tumors ≤ 10mm decreasing significantly to the control level.
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