ESTRO 2024 - Abstract Book

S474

Clinical - Breast

ESTRO 2024

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 < 0.01). For patients with malignant subtypes, there was a noticeable tendency for a lower occurrence of LR in those who underwent adjuvant RT (12.2% vs. 36.4% without RT, p 0.08). 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.