To quote the abstract
BACKGROUND: Malignant phyllodes tumor is a rare and potentially aggressive breast neoplasm. Little information is available regarding the optimal management of these lesions and rarer still are data regarding survival. The current study used a large population database to determine prognostic factors that predict cause-specific survival (CSS). METHODS: Data were obtained from the Surveillance, Epidemiology, and End Results Program (SEER) for the years 1983-2002. Women receiving resection for primary nonmetastatic malignant phyllodes tumor of the breast were included (n = 821). Analyses of patient, pathologic, and treatment characteristics were performed using univariate and multivariate Cox regression analyses for the CSS endpoint. RESULTS: With a median follow-up of 5.7 years, CSS was 91%, 89%, and 89%, at 5, 10, and 15 years, respectively. Mastectomy was performed in 428 women (52%) and wide excision or lumpectomy in 393 (48%). Women undergoing mastectomy were significantly older (P = .004) and had larger tumors (P = .009). Wide excision was associated with equivalent or improved CSS relative to mastectomy on univariate and multivariate analyses. Older age predicted for cause-specific mortality on multivariate analysis. Adjuvant radiotherapy (RT) predicted for worse CSS when implemented compared with surgery alone. CONCLUSIONS: Mastectomy was not found to provide a benefit in CSS compared with wide excision in malignant phyllodes tumor of the breast. Women undergoing wide excision had at the minimum similar cancer-specific mortality compared with those who received mastectomy. The role of adjuvant RT is uncertain and requires further investigation. (c) 2006 American Cancer Society.

Few References for Bed time reading

1. http://www.ncbi.nlm.nih.gov/pubmed/18234448

A large retrospective study of patients with malignant phyllodes tumors treated with surgical resection alone revealed suboptimal five-year local control rates (79 percent in 169 patients treated with wide excision and 91 percent in 207 patients treated with mastectomy). The authors concluded that for patients with malignant phyllodes tumors, particularly over 2 cm in diameter and treated with wide excision alone, adjuvant RT should be strongly considered. One important limitation of this study is the lack of information about margin status.

2. http://www.ncbi.nlm.nih.gov/pubmed/17931796
In a study of 443 women treated for phyllodes tumor, RT was associated with a superior local control rate at 10 years, from 59 percent to 86 percent for borderline and malignant phyllodes tumors.

3.http://www.ncbi.nlm.nih.gov/pubmed/19424757
In a prospective multi-institutional study of adjuvant RT in 46 patients with borderline malignant or malignant phyllodes tumors treated with breast conserving surgery followed by RT, there were no local recurrences with a median follow up of 56 months. Two patients with malignant phyllodes tumor died of metastatic disease.

Taken together, these results indicate that adjuvant RT appears to be effective in decreasing recurrences after breast conserving resection for borderline or malignant phyllodes tumors. Most agree that adjuvant RT is appropriate when it is not possible to obtain a wide margin of ≥1 cm of resection. It is also important to remember that, for some tumors a 1 cm margin may not be possible even with a total mastectomy, due to size or location. In such patients, radiation may be indicated even after a mastectomy.

There is less agreement about the role of adjuvant RT when wide margins ≥1 cm can be obtained. Further studies are needed to determine when adjuvant RT should be advised in the treatment of phyllodes tumors