Objectives: The study analyzes the relationship between the incidence trends of breast carcinoma in situ (CIS) and the spread of mammography screening in the Italian area of Florence (about 608,000 female residents).
Setting: In this area, since the seventies, a mammographic screening by personal invitation was performed by the Center for Cancer Prevention (CSPO) in some rural municipalities. After 1990, the municipality of Florence and other municipalities were involved in the screening.
Methods: The study included all cases of female breast carcinomas in situ reported to the population-based Tuscany Cancer Registry between 1985 and 1995. On the basis of information from the CSPO files, the cases were categorized into: "screen-detected", "self-referrals", and "other" (CSPO cases diagnosed in symptomatic women or at periodic check up after breast cancer plus hospital cases).
Results: Overall, 332 women with breast carcinoma in situ (CIS) were registered between 1985 and 1995. The CIS incidence rate increased from 2.39/100,000 women in 1985-87 to 6.22/100,000 in 1994-95. The largest increase was observed for the ductal carcinoma in situ (2.9 times) and in women aged 50-69 years (3.8 times). In this age group, cases diagnosed at the screening by personal invitation accounted for 69% of the rise in CIS incidence. The proportion of mastectomy lowered from 41% before 1990 to 25% after 1990.
Conclusion: In the Florence area the CIS incidence trend, showing a marked increase beginning in 1991, was mainly explained by the spread of the mammographic screening by personal invitation. The period during which mammographic screening became widespread coincided with a change in the treatment policy of breast cancer, with a high proportion of breast conserving surgery also for CIS. Therefore, the rise in CIS incidence rates correlated with the widespread use of mammographic screening did not substantially increase the number of women treated by mastectomy.