Stage-specific incidence of breast cancer before the beginning of organized screening programs in Italy.

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.