Evaluation of a breast cancer nomogram for predicting risk of ipsilateral breast tumor recurrences in patients with ductal carcinoma in situ after local excision

Abstract

Purpose: Prediction of patients at highest risk for ipsilateral breast tumor recurrence (IBTR) after local excision of ductal carcinoma in situ (DCIS) remains a clinical concern. The aim of our study was to evaluate a published nomogram from Memorial Sloan-Kettering Cancer Center to predict for risk of IBTR in patients with DCIS from our institution.

Patients and methods: We retrospectively identified 794 patients with a diagnosis of DCIS who had undergone local excision from 1990 through 2007 at the MD Anderson Cancer Center (MDACC). Clinicopathologic factors and the performance of the Memorial Sloan-Kettering Cancer Center nomogram for prediction of IBTR were assessed for 734 patients who had complete data.

Results: There was a marked difference with respect to tumor grade, prevalence of necrosis, initial presentation, final margins, and receipt of endocrine therapy between the two cohorts. The biggest difference was that more patients received radiation in the MDACC cohort (75% at MDACC v 49% at MSKCC; P < .001). Follow-up time in the MDACC cohort was longer than in the MSKCC cohort (median 7.1 years v 5.6 years), and the recurrence rate was lower in the MDACC cohort (7.9% v 11%). The median 5-year probability of recurrence was 5%, and the median 10-year probability of recurrence was 7%. The nomogram for prediction of 5- and 10-year IBTR probabilities demonstrated imperfect calibration and discrimination, with a concordance index of 0.63.

Conclusion: Predictive models for IBTR in patients with DCIS who were treated with local excision are imperfect. Our current ability to accurately predict recurrence on the basis of clinical parameters alone is limited.

Fig 1.

Kaplan-Meier failure and cumulative incidence plots demonstrating association between predictor variables of ipsilateral breast recurrence after breast-conserving treatment for ductal carcinoma in situ. Association of adjuvant endocrine therapy with Kaplan-Meier (A) failure plot and (B) cumulative incidence; and association of initial mode of presentation with Kaplan-Meier (C) failure plot and (D) cumulative incidence. P value (log-rank test) is provided for each comparison.

Fig 2.

Calibration plots for the nomogram: (A) 5-year nomogram; (B) 10-year nomogram. Patients were grouped by octiles of predicted risk. The x-axis is the nomogram-predicted probability of ipsilateral breast recurrence (IBTR). The y-axis is the observed probability of IBTR (Kaplan-Meier estimates). Dashed line represents the ideal nomogram; circles represent apparent predictive accuracy, calculated by plotting the mean Kaplan-Meier estimate for each octile versus the mean nomogram-predicted probability for patients in each octile.