Clinical Impact of Preoperative Magnetic Resonance Imaging in Breast Cancer

Breast cancer is the most common malignancy affecting women worldwide. ¹ Contrast-enhanced breast MRI (CE-MRI) may often be used for the purposes of staging breast cancer following diagnosis. ² It is highly sensitive and specific for detecting additional sites of disease (including in the contralateral breast), as well as better characterizing the distribution of disease to guide medical and surgical management.^2,3 It can often detect sites of disease that are occult on mammography and breast ultrasound. However, the impact of disease staging with CE-MRI on clinical outcomes in individuals with breast cancer is debated. ²

The recently published systematic review and meta-analysis by Eisen et al ² sought to address this debate. This study summarized the evidence on the effect of preoperative CE-MRI in individuals with newly diagnosed breast cancer on surgical management, need for re-excision, rates of recurrence, and detection of contralateral disease. ² The systematic review included a total of 51 studies, which included 8 randomized controlled trials, 1 prospective cohort study, and 42 retrospective studies. ² It provided a comprehensive dataset of clinical outcomes in individuals with breast cancer with and without preoperative CE-MRI. Although the overall evidence of included studies was considered of moderate to low quality, a large number of studies with consistency in results across different types of study designs helped inform the conclusions of this systematic review and meta-analysis.

Eisen et al ² found multiple improved clinical outcomes with the use of preoperative CE-MRI in individuals diagnosed with breast cancer. Reoperation rates, which encompass re-excision or conversion to mastectomy, were decreased in individuals with preoperative CE-MRI compared to those without it (odds ratio [OR] = 0.73, 95%-confidence interval [CI] 0.63-0.85). Similarly, re-excision rates were also reduced in individuals with preoperative CE-MRI (OR = 0.63, 95%-CI 0.45-0.89). Furthermore, the rate of breast cancer recurrence was also lower in individuals who underwent CE-MRI (hazard ratio [HR] = 0.77, 95%-CI 0.65-0.90). ²

Eisen et al ² found no significant difference in overall survival (OS) and recurrence-free survival (RFS) in breast cancer patients with and without CE-MRI. To put this into context, advances in the management of breast cancer, including systemic therapy, radiation therapy, and the ability to re-treat recurrent disease, have contributed to significantly improved OS rates. Furthermore, several of the included studies in the systematic review reported OS rates >95%, meaning a very large sample size would be required to detect a very small difference in OS between the 2 groups. As a result, the lack of difference in OS rates in the 2 groups is expected.

In line with the findings of this study by Eisen et al, multiple major group guidelines/targets emphasize clinical outcomes related to the need for reoperation, rather than OS. The American Society of Breast Surgeons states the goal of breast cancer care should be “to minimize the number of operations a patient requires. . .to optimize their oncologic outcomes and minimize local recurrence.” ⁴ The United Kingdom National Health Service Breast Screening Programme has set a reoperation rate target no more than 10% for incomplete excision. ⁵ The European Society of Breast Cancer Specialists (EUSOMA) have also established a minimum standard of 80% and target of 90% for the proportion of individuals diagnosed with invasive breast cancer should receive a single breast operation, excluding reconstruction. ⁶

Eisen et al ² identified an increase in the detection of synchronous contralateral breast cancers, as well, which led to a reduction in metachronous contralateral breast cancers (HR = 0.71, 95%-CI 0.59-0.85). This was in line with prior literature, with another meta-analysis of 22 studies reporting an incremental contralateral breast cancer detection rate of 4.1% compared to conventional imaging. ⁷ In some cases, the mammographically occult contralateral malignancy is larger or more advanced than the index lesion, which would have otherwise gone undetected and untreated if a CE-MRI was not performed. ⁷ Moreover, mammographically occult ipsilateral lesions may also be larger than the index tumour in approximately 1 in 5 cases, and these may be missed for surgical management unless incidentally found during the operation. ²

Overall, the study by Eisen et al was comprehensive in summarizing the available literature on the utility of preoperative CE-MRI in individuals with a new diagnosis of breast cancer. Although advancements in treatment have improved OS and RFS to such a degree that CE-MRI may not provide a significant marginal benefit in this regard, other valuable clinical outcomes may benefit including reductions in reoperation and recurrence rates, as well as improved detection of synchronous breast malignancies.