Radiation therapy for malignant phyllodes tumor of the breast: An analysis of SEER data

Malignant phyllodes tumor of the breast (MPTB) accounts for less than 1% of whole breast neoplasm. Surgery is regarded as the primary treatment of choice in patients with MPTB, but the necessity of postoperative radiation therapy (RT) has been a subject of debate. Our aim was to evaluate effects of postoperative RT for MPTB using a large population database.

Using the Surveillance, Epidemiology, and End Results Program (SEER) database (1983-2013), clinico-pathologic prognostic factors were evaluated. Postoperative RT, tumor extent, grade, and lymph node (LN) metastasis were included in the analysis. Univariate and multivariate Cox proportional hazards regressions were performed to evaluate prognostic power of variables on cancer specific survival (CSS).

A total of 1974 patients with MPTB were reviewed. Of these, 825 (42%) and 1149 (58%) patients underwent mastectomy and breast conserving surgery (BCS), respectively. In each group, 130 (16%) and 122 (11%) patients received postoperative RT. For patients with adverse risk factors including high grade and large tumor size, postoperative RT was more likely to be performed. In multivariate analysis, age, ethnicity, tumor size, tumor extension and LN status were correlated with prognosis in mastectomy group, while postoperative RT did not affect CSS. In BCS group, age and grade were significant prognostic factors on CSS, meanwhile postoperative RT did not impact CSS in multivariate analysis.

Although patients with more adverse prognostic factors underwent postoperative RT, RT groups were not inferior to non-RT group on CSS regardless of surgery (mastectomy or BCS).