Is full field digital mammography equivalent in performance to screen film mammography? UK perspective

Abstract

Aim: The purpose of this project was to compare the performance of full-field digital imaging (FFDM) with screen film mammography (SFM).

Methods: Data from 24,876 and 32,142 women in SFM and FFDM group respectively was collected retrospectively and comparison was made of the recall rate, breast cancer detection rate and positive predictive value (PPV) for the recalls for the two screening modalities, screen film mammography (SFM) and full field digital mammography (FFDM). Difference in radiologic characteristics of the tumours and tumour type (Ductal carcinoma in situ {DCIS} versus invasive) was also evaluated. Statistical software SPSS (PASW18) was used for data analysis with Pearson chi-square and Mann-Whitney-U test used to compare the two groups. A p value of less that 0.05 was considered to indicate a statistically significant difference.

Results: In the year 2008-2009(SFM group), there was a recall rate of 4.5% and a cancer detection rate of 7.5/1000 in the recalled group. For the year 2009-2010 (FFDM group), there was a recall rate of 4.9% and cancer detection rate of 8.8/1000 in the recalled group. There was no statistically significant difference between the recall rate and cancer detection rate between the two groups (p = 0.157). Within the digital group, there was 88(88%) invasive cancer and 12(12%) non-invasive cancer, whereas within the analogue group, there were 74 (92.5%) invasive cancer and 6(7.5%) non-invasive cancer. Most of the non-invasive cancers in the FFDM group were high grade with only one mixed low-intermediate grade. In the analogue group, 50% were high grade, rest being low or intermediate grade. The histological distribution of cancer between two groups was not found to be statistically significant (p = 0.108).

Conclusion: Our study demonstrated FFDM was similar to SFM in terms of cancer detection rate, recall rate and positive predictive value for recalls.