Interval cancers in the beginning years of the breast cancer screening programme in the Belgian province of Limburg

Objective To assess the occurrence of interval breast cancers among those women who attended the mammography screening programme in the Belgian province of Limburg. Interval cancers are tumours that are being diagnosed before the next scheduled screening round and are related to the sensitivity and the screening interval. Methods Biennial screening is provided to all women aged 50-69. The records of the screening programme were linked to those of the cancer registry. The interval cancer rate, expressed as a proportion of the underlying (expected) breast cancer incidence rate was calculated. The observed interval cancer incidence is the number of interval cancers per 10,000 'negative' screening tests. Results The interval cancer rate in the first year was 25.37% for all cancers (ductal carcinoma in situ included) and 21.7% when the analysis was restricted to invasive tumours. Proportional incidence of interval cancer in the second year after screening was 12.02% for all cancers. Conclusion In conclusion, the interval cancer rates in the Belgian province of Limburg were compatible with the European guidelines. However, increasing the recall rate in our programme and systematically reviewing the interval cancers may improve the quality of the programme even further.