Screen-detected breast cancer: does presence of minimal signs on previous mammograms predict staging/grading of cancer?

The previous mammograms of 148 patients with screen-detected breast cancer were examined at Breast Test Wales, Cardiff. Women who showed 'minimal signs' on previous screen mammograms formed the study group. Age, average size of tumour, tumour characteristic, grade and lymph node status were compared to a control group, which had normal previous mammograms. Student t-test and chi-square test were used, with P-value < 0.05 being taken as significant. Images were interpreted first by a senior registrar and then by a breast radiologist who was blinded to the results of current mammograms.

The average age of all the patients was 68.9 years and the mean interval between the two screening mammograms was 44.75 months; 17.56% showed minimal signs at the site of the tumour on previous screen mammograms and formed the study group. There was no statistically significant difference between the two groups with respect to age, average size of tumour, grade or lymph node status, with P-values being 0.609, 0.781, 0.938 and 0.444, respectively. The only statistically significant difference was more microcalcifications seen in the study group (P = 0.003). Five patients in the study group showed positive lymph node or were greater than 2 cm and, therefore, may have had possible gain from earlier diagnosis.

This study did not demonstrate a statistical difference in grading/staging between cancers with minimal signs on previous mammograms and those with normal previous mammograms.