Relationship between the method of detection and prognostic factors for breast cancer in a community with a screening programme

Objectives To analyse and compare the prognostic factors of breast cancer in the target population of our community-screening programme as a function of the method of detection and to analyse the differences in the prognostic factors as a function of the patient's age and the screening episode. Setting A Breast Cancer-Screening Programme (BCSP) in Northeast Spain. Methods Observational study of all primary malignant breast lesions diagnosed in a woman between 50 and 69 years of age between 18 October 1995 and 31 December 2002. The 16 centres that women from the target population might have attended were contacted. Results A total of 225 (37.2%) of the lesions included were diagnosed through the BCSP, 59 (9.7%) interval cancers were detected, and 321 (53.1%) were detected through other circuits. Node involvement was significantly lower in the lesions detected at screening (32%) in comparison to the interval cancers (41.8%) and those detected through other circuits (47.5%). A significantly larger percentage of the interval tumours (28.6%) and the lesions diagnosed outside the BCSP (22.1%) scored > 5.4 on the Nottingham Prognostic Index (NPI) than those diagnosed within the programme (10.9%). The relation between the NPI and the detection method was only statistically significant in the 65-69-year-old age group. The NPI score of the tumours detected by the BCSP showed a statistically significant association with age. Conclusion This analysis has shown notable differences in some prognostic factors for breast cancer according to the method of detection. Association between age and the a priori prognosis of the malignant lesions arises.