Breast‑conserving therapy versus mastectomy in malignant phyllodes tumor of the breast: a propensity score-matched survival analysis and prognostic nomogram

Malignant phyllodes tumor of the breast (MPTB) is rare but aggressive fibroepithelial neoplasms. This study aimed to compare long-term survival outcomes between Breast-conserving therapy (BCT) and mastectomy in patients with stage T1‑3N0M0 MPTB and to develop a prognostic nomogram. METHODS: We identified 683 female patients with stage T1‑3N0M0 MPTB from the SEER database (2010‑2017). Overall survival (OS) and breast cancer‑specific survival (BCSS) were analyzed using Kaplan‑Meier and Cox regression. A nomogram predicting 3‑ and 5‑year OS was constructed and validated. RESULTS: After matching, 282 patients remained in each group. In unadjusted Kaplan‑Meier analysis, BCT was associated with significantly better BCSS (P = 0.0048) and OS (P = 0.017) compared with mastectomy. However, multivariate Cox regression revealed that BCT was not an independent predictor of BCSS (P = 0.355) or OS (P = 0.789). Independent adverse prognostic factors for OS included age ≥ 50 years and T3 stage. The nomogram showed moderate discrimination, with a C‑index of 0.706 (95% CI: 0.524-0.888) in the training cohort and 0.764 (95% CI: 0.543-0.984) in the validation cohort. Although overall prediction error was low in both cohorts, calibration drift was observed in the validation cohort. CONCLUSIONS: After adjusting for confounding factors, BCT was not independently associated with inferior long-term survival compared with mastectomy. When negative margins can be achieved, BCT is a reasonable surgical option. The proposed nomogram may assist in individualized risk assessment, but requires further external validation before clinical implementation.