Early assessment of a population-based breast cancer screening program

Abstract

1018 Background: The reduced mortality rate from breast carcinoma among women offered screening mammography is usually observed after 10 years of follow-up. However, the assessment of 5-year overall and event-free survival could represent an earlier measure of the efficacy of mammography screening. Methods: All cases of breast cancer diagnosed in the Province of Modena between years 1996 and 2000 in women aged from 50 to 69 years, identified through the Modena Cancer Registry were linked to the data-base of the screening mammographic program (SMP), allowing the identification of cases with invasive or in situ breast cancer diagnosed in women attending or not the SMP. Stage of disease and treatment information were obtained from clinical records. All the events occurred up to June 30, 2003 were retrieved by experienced monitors. Five-year overall and event-free survival were the principal end-points of the study. Results: Between January 1,1996 and December 31, 2000, 1058 new breast cancer were detected among women aged 50–69 residents in the Province of Modena. 55% of cases were detected through the screening program. The screen-detected tumors had smaller size (13 vs 19 mm, p<0.0001) were more likely to have a pathologically confirmed negative nodal status (81% vs 62%, p<0.0001), a low histologic grade (25% vs 21%, p< 0.0001), a low proliferative activity (74% vs 61%, p<0.0001), and a positive hormonal status (84% vs 73%, p=0.02). In addition, breast conservative surgery was performed in 75% of SMP participants and in only 54% of non participants. The 5-year estimated survival rate was 94% for women with screen-detected breast cancer and 84% for those with not screen-detected breast cancer (p=0.0001). The rate of 5-year event free survival was 89% and 75% for the SMP attenders and non attenders, respectively (p=0.0001). Conclusions: Our data demonstrate a better prognosis of screen-detected breast cancers in terms of five-year overall and event-free survival, which represent an earlier measure of the efficacy of a population based breast cancer screening program. Finally, a population-based cancer registry is a relevant tool in the evaluation of the program itself. No significant financial relationships to disclose.