Discussion
tumor, death, breast cancer, carcinoma, tumors
RECURRENCES, TUMOR, RECURRENCE, BREAST CANCER, DCIS, CARCINOMA, TUMORS
Our results show that preoperative breast MRI did not change the local recurrence and overall survival rates in breast-conserving surgery candidates. Additionally, preoperative breast MRI increased the mastectomy rates and did not reduce reoperation rates.Only a few studies have examined the long-term outcome effects of preoperative MRI. A previous systematic review that included 3169 patients with published studies until 2012 demonstrated that 8-year disease-free survival did not differ between the MRI (89.0%) and no-MRI (93.0%) groups (Despite local recurrence-free survival early data with 6-year follow-up in our trial, it corroborates with those data. These results may be due to the benefit of radiotherapy in treating undetected findings in the control group and due to the benefit of adjuvant systemic treatment as described in the multivariate analysis of this cohort study where radiotherapy and endocrine therapy were independent factors to prevent local recurrence with a benefit of 86% varying 93% to 70% according to the confidence interval for both treatments. In this cohort, there was an increase in the percentage of adjuvant chemotherapy in the MRI group, explained by the largest median tumor in this group, although this fact did not have an impact on the local recurrence rate (RR 0.9; 95%IC 0.49–1.59) [The criteria for modifying the surgical management based on additional findings in MRI are different in prospective and retrospective studies published until now. There is an increase in mastectomy rates in most previously published studies when preoperative staging with breast MRI is performed with percentages from 7 to 20% [The core issue about the MRI exam to pre-operatory staging is the unnecessary mastectomies, due to false positive findings. Three out of five clinical trials performed the correlation between breast MRI and histopathological findings [In this trial, no difference in reducing reoperation rates between the MRI and control groups was observed, which remains controversial in the literature. Although retrospective studies showed robust evidence in reducing repeated surgeries [Clinical trial summaries available until 2023Benign diseaseIC and DCIS**IC invasive carcinoma; DCIS: Ductal in situ carcinoma*The author not described the stage tumor**The author included B3, B4 and B5 at breast exam. In the MRI group were 39 IC and 39 DCIS, and 38 IC and 41 DCIS***The author included neoadjuvant treatment and did not describe the stage tumorThere are five randomized studies evaluating the impact of conservative surgery on surgical planning, all of them had objective final mastectomy rates and repeat surgery [The design of our trial has two novel strengths. To the best of our knowledge, the BREAST-MRI trial is the first to use randomized stratification based on mammographic density to evaluate the performance of breast MRI in different subgroups. Furthermore, the selection of a measurable threshold to change surgical indication contributes to the literature by adding an objective criterion to the subjective choice of individual surgeons. Occasionally, the definition of 50% larger may favor breast MRI performance without having any clinical relevance in very small tumors. However, the median tumor size for DCIS and invasive carcinoma in breast MRI was 2.9 cm with an interquartile range of 1.5 cm, and the tumor-to-breast volume ratio was always taken into account when making a decision. So, we believe that there was a real impact when it comes to planning conservative surgeries. As potential strengths of our study, we collaborated with breast radiologists with more than five years of experience that interpreted all imaging exams, and we followed patients rigorously, so there were only four losses on follow-up.This trial's main limitations were the unbalance between groups regarding the use of adjuvant chemotherapy, the lack of the allocation concealment procedure, and unblinding evaluators' outcomes and low rate of local recurrence. Nevertheless, the clinical stages were similar between groups; the protocol for chemotherapy treatment in our institution is based on clinical features, including a tumor size of more than 2.0 cm, which could have led to an increase in this treatment in the MRI group. Despite the lack of allocation concealment procedure, only two patients refused to perform MRI in the intervention arm, and this is very unlikely to impact the outcome. Regarding unblinding evaluators’ outcomes, the mastectomy rates are likely to be influenced, and trying to avoid the detection bias we had 3 senior breast surgeons to perform this decision. The other outcomes (all local recurrences were confirmed by biopsy, death, and reoperation rate) are very objective and unlikely to increase the detection bias. Another issue is the time from randomization to surgery; there is a statistical difference between groups showing ten days more in the MRI group, which is explained by the need for additional biopsy. In both groups, time took at least two months to undergo surgery. This prolonged time may happen due to our institution's characteristic, the biggest tertiary hospital in Brazil, with a massive number of patients with low-quality imaging studies before the referral; this incurs due to the necessity to repeat most of the exams after their first visit at ICESP. The low rate of local recurrence probably occurred due to the sample size calculation was based on a study with 20y-follow-up, to achieve 80% of power in this period, we need almost 5800 participants [As for implications in clinical practice, MRI is widely used in preoperative breast cancer patients leading to higher mastectomy rates with no strong evidence that it could avoid a local recurrence. Our trial has an increase of almost 8% in surgical change to mastectomies and, our early results showed that the use of breast MRI did not impact oncological outcomes. In daily practice, its use should be based on shared decisions with breast cancer patients.Regarding future research, in the era of treatment de-escalation and based on the scientific GAP about local recurrence protection, we believe that the publication of the interim analysis is of essential importance to guide other groups and can also be used as a basis for multicentric studies since this the first trial with local recurrence-free survival as a primary outcome. We also believe that further analysis to assess the cost-effectiveness of breast MRI according to the number of unnecessary biopsies or surgeries must be planned.