Journal of Clinical Oncology, 2005 ASCO Annual Meeting Proceedings.
Vol 23, No 16S (June 1 Supplement), 2005: 520
© 2005 American Society of Clinical Oncology

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Abstract

Screening in women at genetic risk of breast cancer: Results of the UK multicentre study of magnetic resonance imaging (MRI) and X-ray mammography (XRM)

The Institute of Cancer Research, Surrey, United Kingdom

520

Background Genetically predisposed women have an increased risk of breast cancer at an earlier age where dense breasts may reduce the sensitivity of XRM. A multicentre study to evaluate the sensitivity of MRI compared to XRM commenced in the UK in 1997. Methods Women at high risk (>0.9%pa) of breast cancer, based on testing, family history or affected relatives, were recruited from 22 centres. Women were enrolled aged 35 to 49 and offered annual MRI and XRM. Exclusion criteria included previous breast cancer or symptoms of breast cancer. MRI measurement and evaluation followed a published protocol with a defined scoring scheme. Cancers were verified histologically. The 2-view XRM followed national standards. MRI and XRM were independently double read. 838 women were screened for between 2 and 7 years. Results A total of 1861 women-years with both MRI and XRM resulted in 35 detected cancers: 19 by MRI, 6 by XRM, 8 by both, 2 interval. Significantly more cancers were detected by MRI than by XRM (P=0.01). The difference was most marked for women with a BRCA1 mutation (P=0.004). Adding MRI to XRM increases the sensitivity from 40% to 94%. Average invasive tumour size was 15 mm. The number with DCIS and with grades 1–3 were 6, 3,7 and 19 respectively. Biopsy rates per 1000 woman-years were 12.9 (benign) and 17.7 (malignant). Cancer detection rates were 27.1 (prevalence) and 13.0 (incidence). 5/26 were node positive. Conclusions MRI was significantly more sensitive than XRM in cancer detection in both the entire cohort and specifically in the sub-group of BRCA1 carriers. Specificity for both procedures was acceptable. Despite a high proportion of grade 3 tumours, tumours were small and few women were node positive. Annual screening combining MRI and XRM would detect most tumours in this risk group. The high biopsy rates reflect the cancer detection rate and the high level of concern in this population.

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Abstract presentation from the 2005 ASCO Annual Meeting