Clinical Newswire December 10, 2009 (San Antonio USA) - Annual MRI screening may detect breast cancer at an earlier stage in women with BRCA mutations, according to results of a prospective trial presented at the 32nd Annual San Antonio Breast Cancer Symposium.*
Women with BRCA mutations have a 45% to 70% increased risk of developing breast cancer by age 70. An earlier study by lead researcher Ellen Warner, MD, MS.c. of Toronto-Sunnybrook Regional Cancer Centre, Toronto found that the sensitivity and specificity of MRI screening in women with high breast cancer risk were 75% and 96%, respectively, compared to 32% and 99% with mammography. When used together, MRI plus mammography yielded a sensitivity of 84% and specificity of 95%. The aim of this study was to determine if adding MRI to mammography surveillance reduces mortality for high risk women.
The MRI cohort consisted of 445 women who were screened with MRI, mammography, and other conventional screening methods, while the control cohort of 830 women were screened with mammography and conventional screening methods only. The MRI patients were from the Toronto-Stonybrook Centre and the control patients were recruited from 13 centers across north America. All subjects had BRCA1 or BRCA2 mutations. In the MRI cohort, 20% of the women had previous breast cancer compared with 44% of controls. The primary endpoints were distant recurrence rates and overall survival. The secondary endpoints were breast cancer incidence and stage. The cumulative incidences of ductal carcinoma in situ (DCIS) and invasive cancer were estimated at 6 years.
At 6 years, 41 (9.2%) women in the MRI cohort and 76 (9.2%) in the control cohort had been diagnosed with breast cancer. Among these women, 12% in the MRI cohort and 34% in the control cohort had previous breast cancer. The cumulative incidence of DCIS was 2.2% in the MRI cohort and 1.1% in the control cohort (p=0.08).
Among women with invasive cancer, in the MRI cohort tumor size was 0-5 mm in 29%, 6-10 mm in 45%, 11-20 mm in 23%, and >20 mm in 3%. In the control cohort, tumor size was 0-5 mm in 8%, 6-10 mm in 27%, 11-20 mm in 36%, >20 mm in 29% (p=0.002 vs MRI cohort), and size data were missing in 8%. The mean tumor size was 9 mm in the MRI cohort versus 18 mm in the control cohort (p=0.0001). In the MRI cohort, 13% of cases were node positive versus 40% in the control cohort (p=0.009).
The cumulative incidence of stage II-IV breast cancers at 6 years was 2.0% in the MRI cohort versus 7.1% in the control cohort (p=0.02). Adjusted hazard ratios in the MRI cohort were 5.72 for DCIS (p=0.007), 1.01 for invasive cancer (p=0.95), 3.02 for stage I cancer (p=0.0002), and 0.27 for ≧stage II cancer (p=0.005).
According to Dr. Warner, limitations of the study included the high proportion of women with previous cancer, the lack of randomization, and differences in the MRI cohort. This study shows that MRI surveillance results in a significantly favorable stage shift in women with BRCA mutations. This finding supports the likelihood that MRI surveillance lowers breast cancer mortality. Longer follow-up of the unaffected subset of each cohort is needed. Dr. Warner concluded that breast surveillance is a reasonable option for women with BRCA1 or BRCA2 mutations.
*Warner E, Hill KA, Causer P, et al. A prospective study of breast cancer incidence and stage distribution in women with a BRCA1 or BRCA2 mutation under surveillance with and without MRI. SABCS 2009. Abstract 26.
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