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

Abstract

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.

Development and Validation of a Prediction Model for Positive Margins in Breast-Conserving Surgery

“…Previous studies have reported several models ( 13 – 18 ) ( Table 4 ). However, most previous models were based on the definition of a positive margin proposed earlier than 2014.…”

“…To date, only two models have been constructed using the revised definition ( 13 , 18 ). However, the conclusion obtained from Ellbrant’s study may be not applicable to Chinese patients because breast density and size varies from foreign to Chinese women ( 26 ).…”

“…For example, accurate axillary nodal stage relays on pathological methods and is only obtained after surgery. Several nomograms exist that can predict the breast-conserving margins using preoperative massage ( 13 – 18 ), however, most nomograms are based on the prior definition of “positive margin” that was revised in 2014 ( 19 ). Therefore, this study aims to identify the preoperative predictors of margin status to develop a nomogram for predicting operative margins.…”

Evaluating the relevance of surgical margins. Part one: The problems with current methodology

“…Currently, there are very few publications that are directed at influencing or directing appropriate surgical dosing, or at providing the surgeon with objective information to determine the optimal treatment strategy for an individual patient prior to a surgery being performed. 108,116,117 Most of the existing literature on prognostic markers has focused on providing stratification of outcome for a surgery that has already been performedproviding information in hindsight of a treatment that has been completed.…”

Updates and Debate Concerning Margin Adequacy and Management following Breast-Conserving Surgery

“…Numerous predictors of surgical margin involvement following BCS have been proposed. Various prediction models (i.e., nomograms) have been designed, demonstrating an impressive ability to predict positive margins after BCS and thereby reduce the reintervention rate [107,108]. However, there is lack of agreement on their routine use in clinical practice [109,110].…”