Screening breast MR diagnoses cancer in women with history of LCIS

Women with a history of biopsy-proven lobular carcinoma in situ (LCIS) appear to benefit from the addition of MRI to mammography for annual breast cancer screening. A retrospective study from Memorial Sloan-Kettering Cancer Institute presented Sunday at the 2010 RSNA meeting indicates the application of screening MRI for this at-risk population can double the cancer detection rate. 

LCIS is associated with a 7% to 12% increased relative risk of developing breast cancer, according to the study’s presenter, Dr. Janice Sung. Its presence increases the lifetime risk from 20% to 30%. The time between the original diagnosis of LCIS and subsequent cancer can be long; it’s more than 15 years in half of all susceptible patients.

Few studies have investigated the efficacy of breast MRI screening in this population, however. American Cancer Society guidelines state there is not enough evidence to recommend for or against MRI screening for this population, Sung said.

The Memorial Sloan-Kettering study evaluated the diagnostic history of 226 women with LCIS who underwent annual screening breast MRI and screening mammography at the institute between 2003 and 2008. Of 860 breast MRI procedures performed on the study population, 693 were screening exams.

About one-third of the subjects had an additional risk factor. These included 28% with a family history of breast cancer and six patients with a personal history of breast cancer. Ages of the subjects ranged from 25 to 76 years, with a median age of 47 years. The median time from diagnosis of LCIS to the first MR screening exam was two years with a range of less than one year to 19 years.

Overall, 17 cases of cancer were detected in 14 patients. Twelve were detected on MRI only, representing a 4.4% malignancy detection rate for the modality, Sung said. Five were detected on mammography only, and no malignancy was identified on both modalities.

Of the 12 cancers in 10 patients detected on MRI, four represented incidental cancers seen first on screening breast MR. The patients ranged in age from 39 to 59 years at the time of diagnosis, with a mean of 52 years. Two of the 10 patients diagnosed with breast cancer had an additional risk factor for the disease. In both instances, the additional risk factor was a family history of breast cancer. Mean time interval from the original diagnosis of an LCIS to the detection of a malignancy was five years.

The invasive cancers detected with MRI were small, ranging in size from 0.05 to 1.3 cm with a mean of 0.9 cm. Three patients had axillary nodal involvement.

Calcifications were present in all five cases missed with screening MRI. Three of the five had an additional, family history, risk factor for breast cancer. And the mean time interval from original diagnosis of LCIS to the detection of cancer was four years.

More biopsies were recommended on the basis of suspicious findings on MRI than on mammography. During the study period, more than 25% of patients had a recommendation for a biopsy at some point.

The positive predictive value of biopsy was similar between the two groups. The sensitivity of MRI was higher than mammography’s (70% versus 35%). But MRI had a lower specificity rate. This pattern of higher sensitivity and lower specificity has been seen previously in studies examining MRI’s value for screening general populations, Sung said.

In response to a question from moderator Dr. Jay A. Baker, division chief of breast imaging at Duke University, Sung admitted to possible patient selection bias to explain the high cancer rate among women with a history of LCIS participating in the study. Despite this limitation and the need for more studies, the findings suggest to Sung and her colleagues that screening breast MRI should be considered for women with a history of LCIS.