A Novel Prognostic Nomogram for Predicting Risks of Distant Failure in Patients with Invasive Breast Cancer Following Postoperative Adjuvant Radiotherapy

Abstract

Purpose: This study aimed to identify predictors for distant metastatic behavior and build a related prognostic nomogram in breast cancer.

Materials and methods: A total of 1,181 patients with non-metastatic breast cancer between 2003 and 2011 were analyzed. To predict the probability of distant metastasis, a nomogram was constructed based on prognostic factors identified using a Cox proportional hazards model.

Results: The 7-year overall survival and 5-year post-progression survival of locoregional versus distant recurrence groups were 67.6% versus 39.1% (p=0.027) and 54.2% versus 33.5% (p=0.043), respectively. Patients who developed distant metastasis showed early and late mortality risk peaks within 3 and after 5 years of follow-up, respectively, but a broad and low risk increment was observed in other patients with locoregional relapse. In multivariate analysis of distant metastasis-free interval, age (≥ 45 years vs. < 45 years), molecular subtypes (luminal A vs. luminal B, human epidermal growth receptor 2, and triple negative), T category (T1 vs. T2-3 and T4), and N category (N0 vs. N1 and N2-3) were independently associated (p < 0.05 for all). Regarding the significant factors, a well-validated nomogram was established (concordance index, 0.812). The risk score level of patients with initial brain failure was higher than those of non-brain sites (p=0.029).

Conclusion: The nomogram could be useful for predicting the individual probability of distant recurrence in breast cancer. In high-risk patients based on the risk scores, more aggressive systemic therapy and closer surveillance for metastatic failure should be considered.

Keywords: Adjuvant radiotherapy; Breast neoplasms; Neoplasm metastasis; Nomogram; Prognosis.

Fig. 1.

Survival time according to the initial patterns of failure after postoperative radiotherapy: overall survival (A) and post-progression survival (B).

Fig. 2.

Baseline hazard function plot of overall survival according to the initial pattern of failure after postoperative radiotherapy.

Fig. 3.

Nomogram predicting distant metastatic failure. LA, luminal A; LB, luminal B; HER2, human epidermal growth factor receptor 2; TN, triple negative; DMFI, distant metastasis-free interval.

Fig. 4.

Calibration plot for comparison of predicted and observed 10-year rates of distant metastasis-free interval.

Fig. 5.

Comparison of risk scores according to different metastatic sites (dotted lines: median values).