1. In patients with newly diagnosed breast cancer, preoperative bilateral breast magnetic resonance imaging (MRI) was associated with a decreased risk of contralateral recurrence compared to patients who had not undergone the procedure.
2. While overall disease free survival was improved after imaging, neither unilateral nor bilateral preoperative breast MRI was associated with improvements in local-regional or distant recurrence, limiting the benefit to a reduction of contralateral recurrence.
Evidence Rating Level: 2 (Good)
Study Rundown: Although mammography is the standard modality for breast cancer screening, false negatives may still occur, particularly in women with dense breasts. As magnetic resonance imaging (MRI) may better characterize breast tissue and evaluate abnormalities on a mammogram, it is increasingly considered an important complementary modality in the evaluation of breast cancer. Despite agreement on the increased sensitivity of breast MRI over conventional methods of breast cancer detection, the results of prior studies have disagreed on the potential benefit of such a multimodal approach in preoperative evaluation of the breast. The current study sought to investigate the effect of preoperative breast MRI utilizing the newest imaging techniques in a matched-cohort analysis with a specific comparison of the risk reduction for recurrent disease between unilateral and bilateral imaging. Cohorts were formed of women with newly diagnosed breast cancer who underwent curative surgery matched for age, grade, stage and molecular features differing only in their receipt of preoperative breast MRI. The authors found that patients who had underwent preoperative imaging showed a significant reduction in overall recurrence rates and a lengthened disease-free survival period than those who had not undergone preoperative breast MRI. Specifically, bilateral imaging reduced the incidence of metachronous cancer in the contralateral breast in women with unilateral breast cancer, but no changes in local-regional disease free recurrence were noted with either unilateral or bilateral imaging.
The statistical power of the study was limited by a relatively small sample size, with all subjects drawn from a single academic hospital thereby restricting the generalizability of its findings. Additional limitations included a lack of cohort matching for the type of surgery, chemotherapy or radiotherapy received by subjects, and a lack of granularity in the age grouping between patients limiting control for potential age-related effects. Future studies are necessary before widespread adoption of this staging method for patients with breast cancer, with particular expansion and stratification among patients who are receiving breast conserving surgery versus mastectomy across all surgically amenable cancer stages.
In-Depth [retrospective cohort]: A total of 3440 consecutive patients with newly diagnosed breast cancer who had underwent curative surgeries with preoperative breast MRI were selected from a single academic medical center, excluding those with a prior breast cancer history, metastases at diagnosis, or who underwent neoadjuvant therapy. Patients were then matched to those who did not receive preoperative breast MRI on the basis of 11 covariates (including age, grade, stage, estrogen and progesterone receptor status, Ki-67 status and molecular subtype). Patients received either unilateral or bilateral breast MRI based on institutional standard protocols in place during specific time periods. A total of 371 patients pairs were collected during the unilateral imaging period and 97 patient pairs during the bilateral imaging period. Kaplan-Meier survival curves revealed an increase in overall disease-free survival among patients who underwent preoperative breast MRI (Hazard Ratio 0.03; 95% CI 0.04-0.21; p < 0.001). Bilateral breast MRI was associated with an 85% risk reduction for recurrence (p < 0.001), stemming mainly from contralateral breast recurrence risk reduction (p < 0.001). While no overall difference was noted regarding local-regional recurrence (p = 0.180) or distant recurrent (p = 0.178) between the study groups, the group that underwent unilateral breast MRI showed an improvement in local-regional recurrence (Hazard Ratio 0.33, p = 0.032) which was not observed among the bilaterally imaged group (Hazard Ratio 0.26, p = 0.180), believed to be due to differences in spatial resolution between the imaging protocols. No overall significant differences were found in the matched data generated during the unilateral imaging period.
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