Krebswissenschaft und -therapie

Mammography Screening Initially Yields Large Tumors and Several Years Later an Increase in Small Tumors-Transient Medium Sized Tumors Appeared

Abstract

Roland B Sennerstam

Objective: To study tumor size and tumor stage alteration during the first period of mammography screening three randomized samples of breast cancers were sorted out from 1993, 1995, and 1997 and a control group from 1987 two years before screening was introduced in 1989 in the Stockholm Gotland County. Among 2080 patients 989 representing the screened age 50 - 69 years were analyzed in the two age groups 50-59 and 60-69 years. Women were called for screening every 2 years.
Study Design: Tumor size was divided into three size groups: ≤ 10 mm, 10-20 mm, and > 20 mm. From the numbers counted in each group the percent was calculated and the distribution presented in figure bars and numerically in tables. The development during the three years was followed.
Results: In the 1993 sample a significant reduction in tumor size > 20 mm was observed compared to the control group (P<0.001) and was accompanied by an increase in tumors for intermediate tumor size 10-20 mm in the screened age group 60-69 years (P<0.05). There was a significant increase of more favorable tumor stages (Stage I) (P<0.02) and reduction in Stage IIA (P<0.001). In 1995 a similar but reduced tendency was found and in 1997 the difference found so far was equilibrated but a significant increase in tumors ≤ 10mm appeared for the first time in the screened age group 60-69 years. Conclusion: The reduced numbers of tumors > 20 mm found after start of screening explains that screening has yielded about 50% of such tumors compared to the controls of which most are tumor stage II-III. At the same time as screening continues there is first a transient increase in intermediate tumors size and finally an increasing numbers of small tumors ≤ 10 mm resulting in more favorable tumor stages.