Development and validation of nomograms of outcomes for first-line platinum-based chemotherapy for metastatic triple-negative breast cancer: patient-level analysis of five prospective clinical trials in China.

Background: Platinum-based chemotherapy has demonstrated superior efficacy as a first-line treatment for metastatic triple-negative breast cancer (mTNBC), at a cost of higher toxicity. Reliable prognostic tools are needed to refine risk stratification and facilitate individualized treatment discussions. Objectives: To develop and validate prognostic nomograms for overall survival (OS) and progression-free survival (PFS) in patients with mTNBC receiving first-line platinum-based chemotherapy. Design: Patient-level pooled analysis of prospective trial data, with internal and external validation. Methods: Individual patient-level data of 777 mTNBC patients from 5 prospective clinical trials were collected. In total, 445 patients who received first-line platinum-based chemotherapy at our center were included as the PFP-TNBC cohort, which was randomly divided (7:3) into training and validation sets. An independent real-world cohort of 216 mTNBC patients was used for external validation. Multivariable Cox regression was used to construct OS and PFS models based on clinical characteristics, laboratory biomarkers, and regimen choice. Model performance was evaluated using concordance index (C-index), time-dependent area under the curve (AUC), calibration, and decision curve analysis. Results: Both nomograms included the number of metastatic sites and the choice of platinum combination agent. The OS model additionally incorporated baseline cancer antigen 125 and lactate dehydrogenase; the PFS model included liver metastasis, baseline pain, and CA153 and carcinoembryonic antigen. For OS, the C-indexes were 0.67, 0.66, and 0.65 in the training, internal validation, and external cohorts, with AUCs of 0.71-0.74, 0.71-0.75, and 0.69-0.71 for 1-, 2-, and 3-year OS. For PFS, the C-indexes were 0.66, 0.62, and 0.61 in the training, internal validation, and external cohorts, with AUCs of 0.69-0.80, 0.66-0.74, and 0.63-0.72 for 6-, 12-, and 24-month PFS, respectively. Both models demonstrated good calibration and risk stratification identified groups with significantly different survival outcomes (log-rank Conclusion: The PFP-TNBC-OS and PFP-TNBC-PFS nomograms provide practical tools to estimate outcomes in mTNBC patients treated with first-line platinum chemotherapy. While C-index values indicated modest discrimination, time-dependent AUCs showed good accuracy at clinically relevant intervals. These models may aid risk stratification, patient counseling, and shared decision-making in chemotherapy-only settings. Future studies are warranted to evaluate their applicability in the evolving era of chemoimmunotherapy.