MRI screening associated with improved survival in women at high risk for breast cancer

Screening with magnetic resonance imaging (MRI) along with mammography and clinical breast exams may improve survival rates in women at high risk for breast cancer, a new study has found.

Researchers in the Netherlands analyzed long-term results of the Dutch MRI Screening Study to evaluate the effects of screening for breast cancer in four different risk groups: women with a BRCA1 mutation, women with a BRCA2 mutation, women at high cumulative lifetime risk (CLTR) due to family history (30% to 50%), and women at moderate CLTR due to family history (15% to 30%). All women in the study received biannual clinical breast exams plus annual mammography and MRI. The study results were published early online Nov. 15 by the Journal of Clinical Oncology.

Data were analyzed for 2,157 women, 599 of whom carried a BRCA mutation. Ninety-seven cases of primary breast cancer were detected. MRI was more sensitive than mammography for invasive cancer (77.4% vs. 35.5%; P<0.00005) but not for ductal carcinoma in situ (DCIS) (38.5% vs. 69.2%; P=0.388). Patients with BRCA1 mutations were more likely than those in the other three risk groups to have lower mammography sensitivity, larger tumors (>1 cm) at diagnosis, a lower proportion of DCIS, a higher proportion of interval cancer, and a higher proportion of cancer diagnosed before age 30. Rates of cumulative distant metastasis-free and overall survival at six years in BRCA1 and BRCA2 carriers with invasive breast cancer were 83.9% (95% CI, 64.1% to 93.3%) and 92.7% (95% CI, 79.0% to 97.6%), respectively. Both survival rates were 100% in women with invasive cancer in the familial risk groups. Overall, 42.7% of breast cancer cases were detected only on MRI. Although randomization was not possible due to ethical reasons, the authors analyzed results from 26 historical cohorts and found a median overall survival rate of 74.5% (range, 50% to 95%) over five years.

The current study confirmed earlier results in this cohort suggesting that intensive surveillance, including MRI, can detect breast cancer earlier in women at high risk, the authors concluded. Of particular importance, they noted, was the large difference in mammography sensitivity in women with BRCA1 mutations compared with BRCA2 mutations (25.0% vs. 61.5%; P=0.04).

The authors concluded that the sensitivity of MRI is "strongly superior" to that of mammography and that their findings affirm the American Cancer Society's recommendation of annual MRI screening in women with a 20% to 25% CLTR for breast cancer. They also noted that BRCA1 carriers might need more frequent screening, different treatments or different preventive measures given the unfavorable clinical characteristics associated with this mutation.

Another study published early online Nov. 18 by The Lancet Oncology found a benefit in screening mammography for moderate-risk women before age 50. A total of 6,710 U.K. patients younger than 50 who were at moderate risk for breast cancer but who were unlikely to have a BRCA mutation received mammography annually for four years, beginning at study enrollment between Jan. 16, 2003 and Feb. 28, 2007 until Nov. 30, 2009. One hundred thirty-six were diagnosed with breast cancer; of these, 77% were diagnosed at screening, 21% were diagnosed symptomatically between screenings, and 2% were diagnosed symptomatically after missing a scheduled mammogram. Data from two other trials were used for comparison, one the control group of a trial of average-risk women followed for up to 10 years and one a study of women with a family history of breast cancer.

The authors found that cases of invasive cancer in their study were smaller and had a more favorable grade than those in the average-risk comparison group, and were less likely to be node positive than those in either the average-risk or family history comparison group. Predicted 10-year mortality rate was also statistically significantly lower in the current study than in the average-risk comparison group. The authors concluded that yearly mammograms are likely to prevent breast cancer deaths in women at moderate familial risk.