The impact of Adjuvant radiotherapy on Borderline and Malignant Phyllodes Tumors of The Breast

Background: Borderline and malignant phyllodes tumors (PTs) are rare fibroepithelial neoplasms of the breast and have a high local recurrence rate (LRR). The use of adjuvant radiation therapy (RT) for local control has increased in recent decades, but its impact on outcomes remains uncertain. We aim to assess the efficacy of radiotherapy and define the factors that are associated with local recurrence. Material and Methods : The study provides a retrospective review of all patients with borderline and malignant phyllodes tumors of the breast who underwent surgery between 2012 and 2021 at our institute. Medical records were examined for clinical data, tumor characteristics, treatment factors, and follow-up status. The primary endpoint was LRR. Kaplan-Meier and Cox regression models were conducted to determine LRRs and the risk factors correlated with an increased risk of LR. Results: The median follow-up was 4.3 years. A total of 102 patients were analyzed: 50 with borderline and 52 with malignant PTs. Patients who are in the malignant group tend to have a larger tumor size (larger than 10 cm) (63.5% vs. 22% of the borderline, p<0.001). The majority of patients with malignant PT underwent mastectomy (TM) (75% vs. 11% of borderline, p<0.001) and had adjuvant RT (78.9% vs. 8% of borderline, p<0.001). There were two borderline patients who had LR, which occurred after 5 years of follow-up. For malignant PTs, all of those recurred before the 5-year follow-up period. Among patients who did not have adjuvant RT, those with malignant PTs experienced a significantly greater rate of LR compared to those with borderline PTs (36.4% vs. 4.4%, p < 0.010). In patients with malignant subtypes, adjuvant RT was associated with a lower local recurrence rate however, the difference was not statistically significant (12.2% vs. 36.4% without RT, p=0.081). The 5-year LRRs of patients with malignant PTs who underwent breast-conserving surgery (BCS), BCS with RT, TM, and TM with RT were 33.3%, 20%, 37.5%, and 9.1%, respectively (p=0.286). In multivariate analysis, the subtype of the tumor (borderline vs. malignant) was the only risk factor that was associated with LR in all patients (p=0.011). Age, tumor size, type of surgery, receiving adjuvant RT, and resection margin were not shown to be correlated with LR in patients with malignant subtypes. For patients who have malignant PTs and underwent adjuvant RT, the timing of RT after surgery (later than 12 weeks) was the only risk factor associated with LR (p=0.009). The use of different radiation techniques (3D vs. intensity modulated radiation therapy), radiation doses (50–60 Gy vs. 60–66 Gy), or the application of a bolus did not show an evident association with LR in this group of patients. Conclusion: This is to confirm that patients with malignant PTs had a higher LRR compared to borderline PTs. In our study, a statistically significant benefit of adjuvant RT was not observed in either borderline or malignant PTs. However, there was a trend toward the efficacy of adjuvant RT in reducing the incidence of LR in cases of malignant PTs.