Nomograms for Estimating Cause-Specific Death Rates of Patients With Inflammatory Breast Cancer: A Competing-Risks Analysis

Abstract

Purpose: Inflammatory breast cancer (IBC) is a rare, aggressive and special subtype of primary breast cancer. We aimed to establish competing-risks nomograms to predict the IBC-specific death (BCSD) and other-cause-specific death (OCSD) of IBC patients.

Methods: We extracted data on primary IBC patients from the SEER (Surveillance, Epidemiology, and End Results) database by applying specific inclusion and exclusion criteria. Cumulative incidence function (CIF) was used to calculate the cumulative incidence rates and Gray's test was used to evaluate the difference between groups. Fine-Gray proportional subdistribution hazard method was applied to identify the independent predictors. We then established nomograms to predict the 1-, 3-, and 5-year cumulative incidence rates of BCSD and OCSD based on the results. The calibration curves and concordance index (C-index) were adopted to validate the nomograms.

Results: We enrolled 1699 eligible IBC patients eventually. In general, the 1-, 3-, and 5-years cumulative incidence rates of BCSD were 15.3%, 41.0%, and 50.7%, respectively, while those of OCSD were 3.0%, 5.1%, and 7.4%. The following 9 variables were independent predictive factors for BCSD: race, lymph node ratio (LNR), AJCC M stage, histological grade, ER (estrogen receptor) status, PR (progesterone receptor) status, HER-2 (human epidermal growth factor-like receptor 2) status, surgery status, and radiotherapy status. Meanwhile, age, ER, PR and chemotherapy status could predict OCSD independently. These factors were integrated for the construction of the competing-risks nomograms. The results of calibration curves and C-indexes indicated the nomograms had good performance.

Conclusions: Based on the SEER database, we established the first competing-risks nomograms to predict BCSD and OCSD of IBC patients. The good performance indicated that they could be incorporated in clinical practice to provide references for clinicians to make individualized treatment strategies.

Keywords: SEER; cause-specific death; competing-risks analysis; inflammatory breast cancer; nomogram.

Figure 1.

Nelson-Aalen curves for each characteristic. (A)-(K) for BCSD, (L)-(Q) for OCSD.

Figure 2.

Competing-risks nomograms for predicting 1-, 3- and 5-year cumulative incidence probabilities for BCSD and OCSD in patients with inflammatory breast cancer. (A) BCSD; (B) OCSD.

Figure 3.

Calibration curves for 1-, 3- and 5-year prediction. (A)-(F) for BCSD; (A)1-year, (B) 3-year, (C)5-year for internal validation; (D) 1-year, (E) 3-year, (F)5-year for external validation. (G)-(L) for OCSD; (G) 1-year, (H) 3-year, (I) 5-year for internal validation; (J) 1-year, (K) 3-year, (L)5-year for external validation.