To investigate the prognostic factors in patients with malignant phyllodes tumors of the breast (MPTB), and establish a predictive nomogram.

In accordance with the inclusive and exclusive criteria, the data of 1 363 patients diagnosed with MPTB in the Surveillance, Epidemiology and Results (SEER) database of the U. S. National Cancer Institute were analyzed in this study. The Kaplan-Meier survival analyses were performed to evaluate the cause-specific survival (CSS) of MPTB patients. The log-rank test was used to explore the relationship between clinicopathological characteristics and CSS. Multivariate analysis by Cox proportional hazards regression model was performed to analyze the prognostic factors from the variables with a significant difference in univariate analysis. The nomogram was developed to predict the CSS of the MPTB. The C-index and calibration plots were generated to evaluate the accuracy of the nomogram.

(1) The 1-year, 2-year, 5-year, and 10-year CSS of 1 363 patients were 97%(1322/1 363), 94%(1 285/1 363), 91%(1250/1 363), and 89%(1 234/1 363), respectively. (2) Univariate analysis found that age, tumor size, tumor stage, marital status, and regional lymph node status were related to CSS of MPTB patients(χ²=55.135, 120.215, 249.650, 5.230, 215.208, all P<0.050). (3)Multivariate analysis showed that the independent factors for the prognosis of MPTB patients were as follow: age (≤45 years vs 45-68 years: HR=2.490, 95%CI: 1.466-4.229, P=0.001; ≤45 years vs ≥68 years: HR=5.296, 95%CI: 2.890-9.704, P<0.001), tumor size(≤59 mm vs 59-115 mm: HR=2.187, 95%CI: 1.421-3.366, P=0.002; ≤59 mm vs ≥115 mm: HR=3.846, 95%CI: 2.395-6.174, P<0.001), tumor stage (local vs regional: HR=2.353, 95%CI: 1.409-3.929, P=0.001; local vs distant metastasis: HR=10.195, 95%CI: 5.187-20.038, P<0.001) and positive regional lymph node (HR=4.830, 95%CI: 1.883-12.387, P=0.001). (4) The four factors (age, tumor size, tumor stage and regional lymph node status) were used to generate a nomogram predicting the CSS of patients diagnosed with MPTB. The C-index was 0.82. The calibration plots showed a good predictive ability of the model.

MPTB patients at advanced age or with large tumors, local progression and metastasis have a poor prognosis, and early detection and treatment is important for MPTB patients.