Prospective findings in breast cancer kindreds: annual incidence rates according to age, stage at diagnosis, mean sojourn time, and incidence rates for contralateral cancer

Abstract

2102 women over 55 years of age from breast cancer kindreds as clinically defined were examined with annual clinical examination and mammography every second year. Initially, all family histories were obtained and all women were invited for genetic counselling. During screening, 37 infiltrating cancers (CA) and 9 carcinomas in situ (CIS) were found. Annual incidence rates for CA or CIS were calculated to be 0.82% for those aged 30 years or more. Annual incidence rate for contralateral cancer among those who had contracted one cancer was 6%. In the first round, 17 of 23 cancers (74%) were without spread, and this increased to 20 of 23 (87%) during follow-up. Two of 23 cancers (18%) were CIS at the first round, increasing to 7 of 23 (30%) at follow-up visits. CIS was diagnosed at a younger age than CA. Employing figures for mean sojourn time from sporadic cancer to calculate the annual incidence rate underlying the observation in the first round gave the same incidence as observed during actual follow-up. This indicates that inherited breast cancer progression is comparable with that of sporadic cancer.