Clinical benefit of nomogram for predicting positive resection margins in breast conserving surgery

Defining the relevance of surgical margins. Part two: Strategies to improve prediction of recurrence risk

Due to the complex nature of tumour biology and the integration between host tissues and molecular processes of the tumour cells, a continued reliance on the status of the microscopic cellular margin should not remain our only determinant of the success of a curative-intent surgery for patients with cancer. Based on current evidence, relying on a purely cellular focus to provide a binary indication of treatment success can provide an incomplete interpretation of potential outcome. A more holistic analysis of the cancer margin may be required. If we are to move ahead from our current situation - and allow treatment plans to be more intelligently tailored to meet the requirements of each individual tumour - we need to improve our utilisation of techniques that either improve recognition of residual tumour cells within the surgical field or enable a more comprehensive interrogation of tumour biology that identifies a risk of recurrence. In the second article in this series on defining the relevance of surgical margins, the authors discuss possible alternative strategies for margin assessment and evaluation in the canine and feline cancer patient. These strategies include considering adoption of the residual tumour classification scheme; intra-operative imaging systems including fluorescence-guided surgery, optical coherence tomography and Raman spectroscopy; molecular analysis and whole transcriptome analysis of tissues; and the development of a biologic index (nomogram). These techniques may allow evaluation of individual tumour biology and the status of the resection margin in ways that are different to our current techniques. Ultimately, these techniques seek to better define the risk of tumour recurrence following surgery and provide the surgeon and patient with more confidence in margin assessment.

A Randomized Controlled Trial for Doing vs. Omitting Intraoperative Frozen Section Biopsy for Resection Margin Status in Selected Patients Undergoing Breast-Conserving Surgery (OFF-MAP Trial)

Purpose

Intraoperative frozen section biopsy is used to reduce the margin positive rate and re-excision rate and has been reported to have high diagnostic accuracy. A majority of breast surgeons in the Republic of Korea routinely perform frozen section biopsy to assess margins intraoperatively, despite its long turnaround time and high resource requirements. This study aims to determine whether omitting frozen section biopsy for intraoperative margin evaluation in selected patients is non-inferior to performing frozen section biopsy in terms of resection margin positivity rate.

Methods

This study is a phase III, randomized controlled, parallel-group, multicenter non-inferiority clinical trial. Patients meeting the inclusion criteria and providing written informed consent will be randomized to the “frozen section biopsy” or “frozen section biopsy omission” group after lumpectomy. Patients with clinical stage T1–T3 disease who are diagnosed with invasive breast cancer by core-needle biopsy and plan to undergo breast-conserving surgery will be included in this study. If a daughter nodule, non-mass enhancement, or microcalcification is identified on preoperative imaging, these features must be within 1 cm of the main mass for inclusion in the trial. The target sample size is 646 patients per arm. The primary endpoint will be the resection margin positive rate, and the secondary endpoints include the reoperation rate, operating time, residual cancer after reoperation, residual cancer after re-excision according to the frozen section biopsy result, resection volume, patient quality of life, and cost-effectiveness.

Discussion

This is the first randomized clinical trial utilizing frozen section biopsy for intraoperative margin evaluation and aims to determine the non-inferiority of omitting frozen section biopsy in selected patients compared to performing frozen section biopsy. We expect that this trial will help surgeons perform the procedure more efficiently while ensuring patient safety.

Trial Registration

ClinicalTrials.gov Identifier: NCT03975179; Clinical Research Information Service Identifier: KCT0004606

Validated prediction model for positive resection margins in breast-conserving surgery based exclusively on preoperative data

Background

Positive margins after breast-conserving surgery (BCS) and subsequent second surgery are associated with increased costs and patient discomfort. The aim of this study was to develop a prediction model for positive margins based on risk factors available before surgery.

Methods

Patients undergoing BCS for in situ or invasive cancer between 2015 and 2016 at site A formed a development cohort; those operated during 2017 in site A and B formed two validation cohorts. MRI was not used routinely. Preoperative radiographic and tumour characteristics and method of operation were collected from patient charts. Multivariable logistic regression was used to develop a prediction model for positive margins including variables with discriminatory capacity identified in a univariable model. The discrimination and calibration of the prediction model was assessed in the validation cohorts, and a nomogram developed.

Results

There were 432 patients in the development cohort, and 190 and 157 in site A and B validation cohorts respectively. Positive margins were identified in 77 patients (17.8 per cent) in the development cohort. A non-linear transformation of mammographic tumour size and six variables (visible on mammography, ductal carcinoma in situ, lobular invasive cancer, distance from nipple–areola complex, calcification, and type of surgery) were included in the final prediction model, which had an area under the curve of 0.80 (95 per cent c.i. 0.75 to 0.85). The discrimination and calibration of the prediction model was assessed in the validation cohorts, and a nomogram developed.

Conclusion

The prediction model showed good ability to predict positive margins after BCS and might, after further validation, be used before surgery in centres without the routine use of preoperative MRI.

Presented in part to the San Antonio Breast Cancer Symposium, San Antonio, Texas, USA, December 2018 and the Swedish Surgical Society Annual Meeting, Helsingborg, Sweden, August 2018.

Predicting initial margin status in breast cancer patients during breast-conserving surgery

Background

We sought to develop and validate a model for prediction of initial margin status during breast-conserving surgery (BCS).

Methods

We included eligible breast cancer patients receiving BCS in Sun Yat-sen Memorial Hospital from January 2003 to December 2014. All patients received intraoperative frozen-section analysis for initial margin assessment. We used univariate and multivariate logistic regression analyses to screen for predictors. A nomogram was developed in the training cohort (n=1,193) from the south branch of the hospital and externally validated in the validation cohort (n=499) from the north branch. We used the area under the receiver-operating characteristic curve and Hosmer–Lemeshow tests to assess the discrimination and accuracy of the nomogram.

Results

The initial margin-positivity rates were 19.5% and 25.2% in the training and validation cohorts, respectively. Preoperative tumor size, preoperative lymph-node status, suspicion of multifocality, hormone-receptor status, and HER2 status were significantly associated with margin status. The model included these five variables. The discrimination and calibration of the model were considered acceptable in both cohorts.

Conclusion

The nomogram can predict the likelihood of having positive initial margins during BCS and may be useful for clinical decision-making in the surgical treatment of breast cancer patients.