Positive margins prediction in breast cancer conservative surgery: Assessment of a preoperative web-based nomogram

•Nomograms in oncology commonly lack results in external validation.•cN1 was found to be a predictive factor of positive margins.•BreastConservation! nomogram is not appropriate for the BC-CHSJ population.

Margin status of the surgical specimen has been shown to be a prognostic and risk factor for local recurrence in breast cancer surgery. It has been studied as a topic of intervention to diminish reoperation rates and reduce the probability of local recurrence in breast conservative surgery (BCS).This study aims to validate the Dutch BreastConservation! nomogram, created by Pleijhus et al., which predicts preoperative probability of positive margins in BCS.Patients with diagnosis of breast cancer stages cT1-2, who underwent BCS at the Breast Center of São João University Hospital (BC-CHSJ) in 2013-2014, were included. Association and correlation were evaluated for clinical, radiological, pathological and surgical variables. Multivariable logistic regression and ROC curves were used to assess nomogram parameters and discrimination.In our series of 253 patients, no associations were found between margin status and other studied variables (such as age or family history of breast cancer), except for weight (p-value = 0.045) and volume (p-value = 0.012) of the surgical specimen.Regarding the nomogram, a statistically significant association was shown between cN1 status and positive margins (p-value = 0.014). No differences were registered between the scores of patients with positive versus negative margins. Discrimination analysis showed an AUC of 0.474 for the basic and 0.508 for the expanded models.We cannot assume its external validation or its applicability to our cohort. Further studies are needed to determine the validity of this nomogram and achieve a broader view of currently available tools.