Tumour characteristics and survival in patients with invasive interval breast cancer classified according to mammographic findings at the latest screening: a comparison of true interval and missed interval cancers

The aim of this study was to investigate whether different mammographic cat egories of interval cancer classified according to findings at the latest s creening are associated with different distributions of prognostic factors or with different survival rates The series consisted of all patients with invasive interval cancer detected from May 1978 to August 1995 (n = 544). T he tumours were evaluated with regard to age, radiological category, interv al between the latest screen and diagnosis and tumour characteristics at th e time of diagnosis. We investigated possible relationships between the sur vival rate of patients with interval cancer and the interval between the la test screen and diagnosis, tumour characteristics and radiological category of the interval tumours. The study focused on Comparison of patients with true interval and missed interval cancer. Women with mammographically occul t tumours were younger than those in the other radiological categories. Com parisons of true interval cancers with overlooked or misinterpreted tumours showed equal distributions of age, tumour size, TNM stage and lymph node s tatus. The overlooked or misinterpreted tumours showed significantly higher proportions of grade-I tumours (22 vs 11%), tumours with low S-phase fract ion (SPF: 44 vs 24%) and oestrogen receptor (ER) positive tumours (72 vs 57 %). However, analyses of survival rates disclosed no clear differences betw een the two radiological categories. Radiological category and interval bet ween the latest screen and diagnosis were not genuine predictors of the pro gnosis in patients with Invasive interval breast cancer. No certain prognos tic difference existed between true interval cancers and overlooked or misi nterpreted interval breast cancers, despite higher proportions of grade-I t umours, ER positive tumours and tumours with low SPF in the latter group.