Breast phyllodes tumors (PT) are rare fibroepithelial neoplasms originating from stromal tissue and account for less than 1% of all breast tumors. The World Health Organization (WHO) classifies PT into benign, borderline, and malignant subtypes based on pathological features such as mitotic activity, cellular atypia, tumor margin invasion, and stromal composition 1. The presence of malignant heterologous elements characterizes the tumor as malignant 2. Surgery is the primary treatment. However, even after R0 resection, borderline phyllodes tumors (BoPT) and malignant phyllodes tumors (MPT) patients remain face a high risk of local recurrence, with rates of 15%-20% and 25%-30%, respectively. Moreover, metastases occur almost merely in MPT, with a distant metastasis rate reaching 22%.

Adjuvant radiotherapy has attracted attention for its potential to improve local control and reduce recurrence, but the role after R0 resection in PT patients remains unclear. Radiotherapy significantly reduces local recurrence rates in BoPT and MPT but shows no substantial benefit in benign cases. However, a meta-analysis by Yu et al. found that this effect is limited to MPT. Additionally, the effect of radiotherapy on survival rates in PT remains controversial. Most existing studies are retrospective and face limitations such as small sample sizes. The rarity of PT and conflicting evidence of impact of radiotherapy necessitate further study. While prospective trials are difficult due to limited cases, well-designed retrospective studies can offer valuable insights. In this study, the investigators also analyzed prognostic factors and identified subgroups to provide a clinical reference for the application of postoperative radiotherapy in BoPT and MPT patients.

Inclusion Criteria:

• patients who were initially diagnosed with BoPT or MPT and underwent R0 resection surgery

Exclusion Criteria:

• patients who had their initial surgery at other hospitals without accurate baseline data
• patients who received radiotherapy before surgery
• those presenting with initial distant metastasis before treatment
• patients lost to follow-up after treatment
• patients with a history of or concurrent breast cancer or precancerous lesions in the ipsilateral breast or with breast cancer in the contralateral breast

Patients pathologically diagnosed with BoPT and MPT who underwent surgery at three medical institutions in China: Sun Yat-sen Memorial Hospital of Sun Yat-sen University, Sun Yat-sen University Cancer Center, and the Third Affiliated Hospital of Nanchang University.

no plan to make individual participant data available to other researchers.