RISK FACTOR-ANALYSIS OF DATA FROM ASSESSMENT CLINICS IN THE UK BREASTSCREENING-PROGRAM - A CASE-CONTROL STUDY IN PORTSMOUTH AND SOUTHAMPTON

Study objectives - The aim was to quantify the influence of demographi c and reproductive factors on breast cancer. The subjects) path throug h the screening clinic, the inherent differences between the control g roups, and the possible biases when using screening programmes were al so considered. Design - A case-control study using both personal conta ct and postal questionnaires to gather demographic and reproductive in formation. Setting - Women attending two breast screening recall clini cs in Portsmouth and Southampton over the period 1990-92. Participants - Altogether 1813 subjects between the ages of 50 and 65 years. The s ubjects' disease status was ascertained using a mammography and classi fied into four categories: 253 breast cancer (cases); 207 benign breas t disease (ED); 410 requiring early rescreen (ER); and 943 for standar d recall (SR). The ED, ER, and SR groups were used as separate control s. Main results - Of the factors considered here, the only two that sh owed a consistently significant effect on the risk of breast cancer we re age and body mass index (BMI). Odds ratios were calculated for five yearly age groups and four groups of BMI using the youngest and Light est group as the baseline, respectively. There seemed to be an increas e in the risk of breast cancer for increasing age for each comparison made (for cases v SR: OR (95% CI) = 1.60 (1.10, 2.34), 2.54 (1.76, 3.6 8)). All subjects above the lowest quartile of BMI experienced increas ed risk, although a trend was not clear (for cases v SR: OR (95% CI) = 1.66 (1.03, 2.66), 1.37 (0.86, 2.20), 1.98 (1.24, 3.15)). Conclusions - Various other potential risk factors were found to be inconsistentl y significant depending on choice of control group. This may help in u nderstanding the differences between the three control groups used.