We report the 5- and 10-year survival rate of women diagnosed with breast cancer in the context of an annual MRI-based surveillance program. In 2001, as part of a national initiative, women in Norway with a BRCA1 mutation were offered annual screening with breast MRI in addition to mammography. 802 women with a BRCA1 mutation were screened one or more times and followed for a mean of 4.2 years. As of December 2011, 68 of 802 women in the screening program were diagnosed with DCIS or invasive breast cancer (8.5 %), including eight prevalent, 50 incident screen-detected and eight interval cancers. Two latent cancers were detected at prophylactic mastectomy. Sixty-three of the cancers were invasive and five were in situ.

The mean tumour size was 1.4 cm (range 0.2-4.5 cm), and 85 % of the patients were node-negative. Ten of the 68 patients died of cancer in the follow-up period. The 5-year breast cancer-specific survival for women with cancer was 75 % (95 % CI 56-86 %) and the 10-year survival was 69 % (95 % CI: 48-83 %). The 5-year survival for women with Stage 1 breast cancer was 82 % compared to 98 % in the population. The 5- and 10-year survival of women with a BRCA1-associated breast cancer detected in a national MRI-based screening program in BRCA1 mutation carriers Norway was less than anticipated. The benefit of annual MRI surveillance on reducing breast cancer mortality in BRCA1 mutation carriers remains to be proven.