Objective: To measure stage-specific geographic and time variability of breast cancer in seven Italian areas before the onset of organized screening programs.
Methods: All invasive cancers (8689 cases) arising in women aged 40-79 years during the pre-screening period 1985-1997, were considered. Multiple Poisson regression analysis was performed.
Results: About 39% of the cases were classified as "early," 52% as "advanced," and 9% as "unspecified" stage. Age-adjusted incidence rates showed a significant geographic variation for early but not for advanced cancers (range: 58-103 cases/100,000 and 104-125 cases/100,000, respectively). The result was confirmed in the multiple regression analysis after adjustment for year of diagnosis and age. Early breast cancer risk adjusted for age and registry showed a significant increase over time (+3.9% per year for all ages, and +6.2% per year for age category 50-79). In contrast, a decreasing time trend was observed for advanced cancer of 3 cm or over in women aged less than 60.
Conclusions: In our study, early breast cancer incidence varied both by geographic area and time before the commencement of screening. The differences in early-stage incidence may well be related to differences in availability of "spontaneous" mammography. Late-stage incidence decreased over time in younger women and for very advanced cases, but not in the older ones, nor for cancers less than 3 cm. Early detection outside organized screening was only partially efficient in reducing advanced breast cancer incidence. The trend of incidence of advanced disease, as previously proposed, is confirmed to be a valid early indicator of effectiveness of screening.