The influencing factors and prognosis analysis of positive initial margin in intraoperative frozen section during breast-conserving surgery

Abstract

Objectives

A critical measure to reduce the risk of ipsilateral breast tumor recurrence after breast-conserving surgery (BCS) for patients with early invasive breast cancer (BC) is ensuring negative margins through frozen section intraoperative margin assessment (FSIMA).This study aims to evaluate the influencing factors and prognosis associated with positive initial margins in FSIMA.

Methods

The clinical data of 436 BC patients treated with BCS were retrospectively analyzed, and long-term follow-up outcomes were evaluated.

Results

Among the 436 patients, approximately 90.8% (396/436) underwent successful BCS, while 71.8% (313/436) exhibited initial negative margins based on FSIMA. A total of 123 patients (28.2%) had positive initial margins, following additional excisions in some cases, 89 patients achieved negative margins. Univariate and multivariate analyses revealed significant differences between the positive and negative margin groups in tumor diameter, distance from the tumor to the nipple, and axillary lymph node metastasis (P < 0.05). No significant differences were observed in disease-free survival or overall survival between the two groups (P > 0.05).

Conclusions

The findings suggest that tumor diameter, the distance between the tumor and nipple, and axillary lymph node metastasis may influence the determination of positive initial margins in FSIMA. Positive initial margins do not appear to influence disease-free survival (DFS) or overall survival (OS) among BC patients treated with BCS.

Introduction

Early stage BC patients undergoing BCS exhibited no clinically significant differences in disease-free survival (DFS) and overall survival (OS) compared to those who underwent mastectomy [1, 2]. Furthermore, BCS can preserve the natural shape of the breast, mitigate psychological trauma resulting from mastectomy, and enhance the quality of life for patients. Consequently, BCS has emerged as the standard surgical approach for early stage breast cancer. However, BCS, as opposed to mastectomy, is associated with a significantly higher risk of local recurrence. Following BCS, the ipsilateral BC recurrence rate for patients with positive margins was at least twice that of those with negative margins, and it could not be eliminated through adjuvant endocrine therapy and tumor bed boost radiotherapy [3, 4]. The key to reducing the ipsilateral BC recurrence risk after BCS is ensuring all margins are negative. Internationally, negative margins are established as a pathological standard, meaning no ink on the tumor. The cavity margin evaluation method defines negative margins as the absence of in situ carcinoma or invasive carcinoma in the margin tissue [5]. Literature surveys indicate that approximately 20–30% of individuals diagnosed with BC experience a recall for surgical intervention when surgical margins were not evaluated intraoperatively, and subsequent examination of the tissue through paraffin pathology reveals the presence of positive or inadequate margins [6, 7]. Accurate assessment of the intraoperative margin can address many of these issues. The use of frozen sections, while it reduces the recurrence rate after BCS, has limitations in terms of sensitivity and can lead to longer operation times [8,9,10]. Thus, a negative initial margin in FSIMA is particularly significant. By examining samples from 436 patients treated with BCS, the study aims to explore the factors influencing a positive initial margin in intraoperative frozen sections during BCS, and to assess its impact on prognosis.

Patients and methods

Patients and eligibility criteria

The retrospective investigation was executed at the Guangdong Women and Children Hospital, focusing on patients who underwent BCS between January 1, 2012, and December 31, 2018.The study was approved by the Ethics Committee at Guangdong Women and Children Hospital (No. 202001092). It was designed with the following inclusion criteria: (i) patients who were pathologically diagnosed with BC at TNM cT1–2 N0–1M0 stage were included during the study period and (ii) surgical margins were evaluated using intraoperative frozen section. The exclusion criteria included: (i) multicentricity; (ii) diffuse calcification; (iii) inability to complete postoperative adjuvant therapy (radiotherapy, chemotherapy, endocrine therapy, or targeted therapy) as per treatment specifications; and (iv) previous history of BC or other malignant tumors before undergoing BCS. A total of 436 patients met the inclusion criteria and participated in the study.

BCS was conducted on all 436 patients, and the post-treatment regimen, which included conventional radiotherapy or adjuvant therapies, such as hormone therapy, chemotherapy, and anti-Her-2 targeted therapy, was determined by the disease stage and the clinical presentation of each patient. The recorded data encompassed patient age, histological grade, axillary lymph node status, estrogen receptor (ER) status, Her-2 status, Ki-67 index, and other relevant factors. All data collected from the participants were anonymized and stored in a prospective database managed by the Breast Disease Center. Supplementary information was sourced from the medical records of the Breast Disease Center.

Procedure for breast conservation

During the operation, the breast tumor was widely excised with a 1.0 cm macroscopic margin. A cavity shave margins excision was also performed. Incisions were made to ensure five specimen margins, approximately 5 mm thick, from the residual cavity (superior, inferior, medial, lateral, and base). The margin specimens were oriented using sutures and transported as frozen sections to the pathology department for intraoperative pathologic analysis. A successful breast conservation surgery is declared when all the intraoperative frozen sections reveal that all resection margins are negative. To localize the tumor bed, titanium clips were placed in the superior, inferior, medial, lateral, and base directions of the residual cavity. If positive margins are noted, an additional 5 mm of tissue is excised to take another margin or mastectomy is performed, depending on the condition.

Pathological evaluation of surgical margins

The tissue intended for freezing was affixed to a cryostat chuck using a tissue freezing medium and subsequently positioned within the cryostat. Sections measuring approximately 10 µm in thickness were obtained, transferred onto slides, and subjected to staining with haematoxylin and eosin (H&E). These slides were then meticulously examined under a microscope by two seasoned pathologists. The median duration of the frozen section procedure amounted to 20 min. A positive margin indicates either in situ carcinoma or invasive carcinoma. All specimens subjected to routine paraffin sectioning are preceded by frozen pathology evaluation. The margin status determined through paraffin sectioning is regarded as the definitive standard.

Follow-up

The cases were subjected to follow-up through outpatient review or telephone until March 31, 2024, achieving a follow-up rate of 97.7%. Disease-free survival (DFS) is defined as the interval between the date of surgery and the identification of tumor recurrence or metastasis (the initial event); overall survival (OS) is defined as the interval between the date of surgery and the date of death attributed to the tumor.

Statistical analysis

The data was subjected to statistical analysis using SPSS version 26.0 software. The evaluation of initial margin positivity in the intraoperative frozen section during BCS was conducted through univariate analysis, employing the chi-square test. Logistic regression was utilized for multivariate analysis, and the Kaplan–Meier method was used for survival analysis. The threshold for statistical significance was set at an alpha level of 0.05 (α = 0.05).

Results

Margins by frozen section during BCS

Of the 436 patients who participated in the study and underwent BCS, 71.8% (313/436) had negative initial margins as indicated by intraoperative frozen section analysis, while 28.2% (123/436) had initial margin-positive outcomes. Within the group that initially had negative margins, 6 individuals showed positive margins upon examination of paraffin sections and subsequently underwent a second BCS operation. Of the patients who initially had margin-positive results, 4 proceeded directly to mastectomy, while the remaining 119 underwent additional resection to achieve negative margins. Ultimately, 89 patients successfully achieved negative margins (see Fig. 1).

Fig. 1

Margins status during BCS

Ultimately, the success rate of BCS was determined to be 90.8% (396/436), with 9.2% (40/436) requiring mastectomy due to positive margins. Approximately 4.4% (19/436) of patients underwent a secondary operation after the intraoperative frozen section analysis indicated negative margins, but the postoperative paraffin section analysis revealed a positive result.

Univariate analysis of initial margin positivity in intraoperative frozen section during BCS

No statistically significant differences were identified in terms of age, menopausal status, pathological nipple discharge, calcification status, preoperative breast magnetic resonance imaging (MRI), histological grade, pathological stage and type, ER status, Her-2 status, and Ki-67 index between patients with positive initial margins and those with negative margins as assessed by intraoperative frozen section (P > 0.05). However, significant differences were noted in tumor diameter, distance from the tumor to the nipple, and axillary lymph node metastasis (P < 0.05, Table 1).

Table 1 Univariate analysis of initial margin positivity in intraoperative frozen section during BCS

Multivariate analysis of initial margin positivity in intraoperative frozen section during BCS

Utilizing positive initial margins as the dependent variable, indicators that demonstrated statistical significance in the univariate analysis—including the distance from the tumor to the nipple, tumor diameter, and axillary lymph node metastasis—were incorporated into a multivariate Logistic regression analysis as independent variables. The findings revealed that the distance from the tumor to the nipple, tumor diameter, and axillary lymph node metastasis were the independent factors affecting initial margin positivity in intraoperative frozen sections during BCS (P < 0.05) (Table 2).

Table 2 Multivariate analysis of initial margin positivity in intraoperative frozen section during BCS

Prognostic evaluation of positive and negative initial margins

The observation period ranged from 37 to 147 months, with a median of 93 months. A total of 42 patients experienced recurrence or metastasis. The DFS rate for the entire cohort was 90.1%, and no statistically significant difference in DFS was observed between patients with negative and positive initial margins (90.8% vs. 88.5%, P = 0.250). The overall local recurrence rate was 5.9%, and there was no significant difference in this rate between the two groups (4.9% vs. 8.2%, P = 0.275). The OS rate  for all patients was 97.7%, and no significant difference in OS was noted between those with negative and positive initial margins (97.7% vs. 97.5%, P = 0.880). (Refer to Table 3, Fig. 2 and 3 for further details).

Table 3 Prognostic evaluation of positive and negative initial margins

Fig. 2

Disease-free survival curves of patients with negative and positive initial margins

Fig. 3

Overall survival curves of patients with negative and positive initial margins

Discussion

A significantly elevated risk of local recurrence has been noted among BC patients who undergo BCS compared to those who undergo mastectomy, a phenomenon that may predominantly be attributed to the presence of residual cancerous cells at the surgical margins [3]. Studies have shown that after BCS, the average treatment duration for BC patients readmitted to the hospital due to positive or inadequate surgical margins identified in paraffin pathology was extended by 26.6 ± 17.9 days, ranging from 9 to 180 days. This not only resulted in increased costs, with an additional approximate expenditure of $2,360 (excluding anesthesia, imaging assessments, and pathology expenses), but also required an extra hour of surgery per patient [11]. It has been globally reported that surgeries assessed using frozen sections for surgical margins are more time-consuming but lead to fewer mastectomies compared to those assessed using paraffin Sects. (48.9 ± 17.3 min vs. 42.9 ± 13.6 min, P < 0.0001) (5.9% vs. 9.7%, P = 0.0202) [12]. In the current study, by evaluating multiple selective margins intraoperatively via frozen section within the residual cavity, it was discovered that 28.2% of patients initially had positive margins, necessitating a second resection. Following the intraoperative frozen section evaluation of surgical margins, only 4.4% of patients required a secondary surgical intervention. Furthermore, this approach reduces the financial burden on patients and is in line with China's national conditions.

A previous investigation substantiated the correlation between positive surgical margins and the presence of metastasis in axillary lymph nodes, as well as the size of the tumor [13]. In the present study, a statistical assessment of the data through univariate and multivariate analyses indicated that tumor diameter, the distance from the tumor to the nipple, and axillary lymph node metastasis could all be factors influencing positive initial margins as determined by intraoperative frozen section analysis. Lombardi, A., et al. have suggested that age might exert an influence on the incidence of positive initial margins [14]; however, the current study indicated that there is no correlation between positive initial margins and age. Mastectomy is commonly recommended for individuals with nipple discharge to ensure complete tumor excision [13, 15]. However, this study found no correlation between pathological nipple discharge and positive initial margins. Although there is a significant risk of recurrence in BC patients who have undergone BCS and present with calcification [16], limited breast calcification did not indicate an increased probability of positive initial margins in strictly selected cases. Bae, M.S., et al., have suggested that the use of a MRI scan before BCS could aid in identifying potential multicentric lesions, thereby decreasing the likelihood of reoperation following BCS [17]. A Phase III randomized, open-label, single-center trial has demonstrated that the implementation of preoperative MRI increased mastectomy rates by 8%. The use of preoperative MRI did not influence local relapse-free survival, overall survival, or reoperation rates [18].In this study, we revealed that prior examination of breast MRI may not affect the positivity of the initial margins. The findings also rejected any association of menopausal status, histological grade, pathological type, ER status, Her-2 status, Ki-67 index and pathological stage with initial positive margins. In terms of prognosis analysis, there was no difference in DFS and OS between the positive initial margin group and the negative initial margin group.

It can be inferred that although the intraoperative frozen section extends the duration of BCS, it effectively reduces the likelihood of reoperation, thereby lowering medical expenses and facilitating subsequent adjuvant treatment. A higher positive rate of initial margins was observed in patients when the distance from the tumor to the nipple was less than 2 cm, the tumor diameter was 3 cm or greater, and there was the presence of positive axillary lymph nodes. BCS should be performed with caution in patients with these conditions, and appropriate expanded resection may ensure a negative initial margin. In the end, positive initial margins do not ultimately affect DFS and OS in patients with BC. This investigation is subject to certain limitations, primarily the insufficient duration of the follow-up period. In general, individuals who opt for breast-conserving surgery are in the early stages of their condition, and recurrence and metastasis events typically manifest several years post-surgery. Therefore, with a follow-up period that is not sufficiently extensive, it is challenging to discern variations in DFS and OS. Even in this study, a trend in mortality differences may be observed after 5 years.