Phyllodes tumors of the breast: Adjuvant radiation therapy revisited

BACKGROUND: Phyllodes tumors (PT) are rare entity and surgical resection is the cornerstone of treatment. No standard of care exists regarding adjuvant treatment especially radiation therapy (RT). PATIENTS AND METHODS: We analyzed all patients with non-metastatic, resected phyllodes tumors who presented to our institution from January 2005 through December 2019. Primary study endpoints included local recurrence free survival (LRFS) and overall survival (OS). RESULTS: One hundred and eight patients were analyzed (patients with incomplete treatment and follow up data were excluded). Fifty patients had benign phyllodes, 26 patients had borderline and 32 patients had malignant phyllodes. In the benign group, no significant difference in LRFS was observed between patients who received adjuvant RT (n = 3) and those who did not (5-year LRFS 100% vs. 85% respectively, p = 0.49). The 5 year OS for patients who received RT was 60% vs. 89% for those who did not (p 0.40). In the borderline/malignant group, adjuvant RT significantly improved five year LRFS (90% in the RT group vs. 42% in the no RT group, p = 0.005). The 5 year LRFS in patients treated with margin negative breast conserving surgery and RT was 100% vs. 34.3% in patients who did not receive RT (p 0.022). Patients treated with mastectomy and RT had a 5 year LRFS of 100% vs. 83% for patients who did not receive RT (p 0.24). On multivariate analysis, radiation therapy was independently associated with decreased hazard of local failure (HR 0.21, CI 0.05-0.89, p = 0.03). No difference in OS was found between the RT and no RT groups (5-year OS was 52% vs. 45% respectively, p 0.54). CONCLUSION: The results of the current study confirm the excellent prognosis of benign phyllodes tumors; warranting no further adjuvant treatment after margin-negative surgical resection. For patients with borderline/malignant phyllodes tumors, adjuvant radiation therapy significantly improved LRFS after margin negative wide local excision; however, patients treated with mastectomy did not attain the same benefit from adjuvant irradiation.