Question

A prospective study of Norwegian women who were followed between 1986 and 2009 was conducted. Within that period (1995-2005), a national mammography program was gradually implement ed, with biennial invitations send to women age 50-69. The participants of the study were all women aged 50-79 between 1986-2009. The mortality rate ratios compared women who were invited to screen to those who were not invited, with a clear distinction between cases of breast cancer diagnosed before and after the invitation to screening. That is the cases of breast cancer before had no potential for the effect of screening. The authors took steps in the analysis to make comparable the time from diagnosis to death from breast cancer among women invited and women who were not invited. After adjustment for age, birth cohort, county of residence, and national trends in deaths from breast cancer, the data on 1 poi mortality rates associated with being invited to mammography screening is presented in the table below: Screening Status Deaths from Breast Cancer Person-Years ...8.996.... 1,175 12,785,325 2,407,709 Not invited Invited Using the crude measure of association (or effect) what is the apparent effectiveness of the invitation to modern mammography on mortality from breast cancer? (Provided an estimate in percent, you can check your answers using the comparison of two rates in Open Epi in this link: http://www.openepi.com/PersonTime2/PersonTime2.htm)

Answer 1

It can be seen that the mortality rate of the women invited is eight times lesser than women who were not invited. It shows that the women under screening were got lot attention and hence they were prevented to die from the breast cancer. On the other hand the women who were not screened, due to poor attention and care were unaware of the precautions and died more frequently.

So the breast cancer related mortality decrease with proper medication, care and attention.