Mammography Screening-Factors affecting Tumour Stage and Outcome

The aim of this thesis was to investigate screening mammography in relation to factors affecting tumour stage and outcome. The main focus was on obesity, tumour biology and breast density. We hypothesized that obese and overweight women could benefit more from screening detection than normal weight women. The favourable prognosis in screening-detected women was further investigated, and we expected screening detected women to have lower levels of tumour markers associated with proliferation and poor prognosis. Finally, the impact of breast density on prognosis was investigated.
For the analyses on obesity, cases were retrieved from the Malmö Breast Cancer Database and screening status was defined according to randomization in the Malmö Mammographic Screening Trial. For studies on molecular characteristics and breast density, cases were retieved from the Malmö Diet and Cancer Study.
In women not invited to screening in the MMST (controls), there was a positive association between obesity and tumour stage. Obese MMST controls also had an increased risk of breast cancer death during follow-up, i.e. a poor survival. In women invited to screening, no association was seen between between obesity and stage or breast cancer death. The examined tumour markers could only explain a minor part of the survival difference between screening-detected vs. clinically-detected women. Breast density was associatd with increased breast cancer mortality regardless of detection mode.
To summarize, obese, as compared to normal weight women, not invited to screening, were diagnosed at a relatively late stage, and had higher breast cancer mortality. These differences were not seen in women invited to screening. Molecular tumour markers could only explain differences in survival according to screening status to a small extent. Breast density was associated with a worse breast cancer survival rate regardless of screening status.