Breast cancer screening – time to move forward

Evaluation of service mammography screening impact in Italy. The contribution of hazard analysis

12,987 invasive breast cancer cases were diagnosed in women aged 50-69 upto the year 2001 in nine Italian areas where a screening programme was active. Cases were followed up in 2005 for a total of 1921 breast cancer failures. The 10-year survival rates were 85.3% for the invited group against 75.6% for the non-invited. A time dependent analysis was performed using 5-year intervals. Crude hazard ratios for the invited group in comparison to the not invited group were 0.52 and 0.64 respectively in the (0-5) year and [5-10] year time windows. Hazard ratio adjusted for tumour characteristics was 0.96 in the [5-10] year time window, suggesting minimal or any length bias. Consistent with the results of randomised trials, these analyses of service screening data document a mortality reduction of 36% at 5-10 years after diagnosis.

Overdiagnosis and overtreatment of breast cancer: overdiagnosis and overtreatment in service screening

Screening mammography has been shown to be effective for reducing breast cancer mortality. According to screening theory, the first expected consequence of mammography screening is the detection of the disease at earlier stages and this diagnostic anticipation changes the population incidence curve, with an observed increase in incidence rates at earlier ages. It is unreasonable to expect that the age-specific incidence will ever return to pre-screening levels or to anticipate a significant reduction of incidence at older ages immediately after the first screening round. The interpretation of incidence trends, especially in the short term, is difficult. Methodology for quantification of overdiagnosis and statistical modelling based on service screening data is not well developed and few population-based studies are available. The overtreatment issue is discussed in terms of appropriateness of effective treatment considering the question of chemotherapy in very early stages and the use of breast conserving surgery.

Early diagnosis, not differential treatment, explains better survival in service screening

Italian population-based breast cancer screening programmes with 2-year, high-quality mammography started in the cities of Florence and Turin in the early 1990s. Breast cancer cases from the local Tumour Registry were classified by method of detection and tumour characteristics (size, nodal-status and grade). Follow-up was at December 2001. In total, 4444 breast cancer cases were analysed. The Hazard Ratio comparing before and after-invitation breast cancer cases indicated a 27% reduction (HR=0.73; 95%CI: 0.61-0.87) in the risk of dying for the disease. After adjustment for tumour characteristics, survival rate was comparable by invitation status, whereas the proportion of early cancer was 33.7% and 46.6% in the before and after-invitation group. Survival rates by tumour characteristic subgroups was comparable by invitation status. Late stage and grade 3 were indicators of poor prognosis. Adjustment for tumour characteristics confirmed screening and not differential treatment as the most important reason for the observed survival benefit. The survival analysis by specific subgroups did not support the hypothesis that the difference in prognosis was attributable to differential treatment.