Background. Malignant phyllodes tumors of the breast have traditionally been treated with surgical excision. Recently, the use of adjuvant radiotherapy has been advocated to reduce the risk of local recurrence; however, this recommendation is controversial in the absence of consistent outcome data. We hypothesize that there has been a trend toward increased utilization of adjuvant radiotherapy for malignant phyllodes tumors despite its uncertain effect on outcomes. Methods. Using the National Cancer Data Base, predictors of radiotherapy utilization were examined for women with malignant phyllodes from 1998 to 2009. Kaplan-Meier and Cox regression models were generated to determine the effect of radiotherapy on local recurrence (LR), disease-free survival (DFS), and overall survival (OS). Results. Of the 3,120 patients with malignant phyllodes, 57 % underwent breast conservation surgery and 42 % underwent mastectomy. Overall, 14.3 % of women received adjuvant radiotherapy. Utilization of radiotherapy doubled over the study period (9.5 % in 1998-1999 vs. 19.5 % in 2008-2009, p < 0.001). Women were significantly more likely to receive radiotherapy if they were diagnosed later in the study, were age 50-59 years old, had tumors >10 cm, or had lymph nodes removed. For the 1,774 patients with available recurrence data, overall recurrence was 14.1 %, and LR was 5.9 %. In adjusted models, adjuvant radiotherapy reduced LR (aHR 0.43, 95 % CI 0.19-0.95) but did not impact DFS or OS after 53 months' median follow-up. Conclusions. Utilization of adjuvant radiotherapy for malignant phyllodes doubled from 1998 to 2009. Radiotherapy significantly reduced LR but had no effect on DFS or OS.
ASJC Scopus subject areas