S1058
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
Digital Poster 5112
localized PMES is debatable. Material/Methods:
Phyllodes Tumors and Recurrence Risk: Durable Local Control after Postoperative Radiotherapy with Moderate Dose Escalation Beatriz Alvarez, Angel Montero, Raquel Ciervide, Jeannette Valero, Mariola Garcia-Aranda, Xin Chen- Zhao, Rosa Alonso, Ovidio Hernando, Mercedes Lopez, Emilio Sanchez, Raquel Sanchez, Bruno Zambrana, Carmen Rubio Radiation Oncology, HM Hospitales, Madrid, Spain Purpose/Objective: Phyllodes tumors (PTs) are rare breast neoplasms with a risk of local recurrence and metastasis, particularly in borderline and malignant cases. Postoperative radiotherapy (RT) has been suggested for high-risk of recurrence PTs, but its efficacy remains underexplored due to the rarity of these tumors and the lack of randomized controlled trials. This study evaluates the outcomes of postoperative radiotherapy with moderate dose-escalation for PTs at risk of recurrence. Material/Methods: We present a retrospective review of 20 women diagnosed with PTs between 2015 and 2024 and with a minimum follow-up of 12 months. Tumors were classified as benign (20%), borderline (40%), and malignant (40%). Postoperative radiotherapy was delivered to the whole breast or chest wall with a median biologically effective dose (BED) of 92.7 Gy (range 90.0–102.6 Gy). Follow-up ranged from 12 to 125 months, and acute and late toxicities were assessed. Indications for post-operative radiotherapy included: close/positive margins no candidates to re- excision (20%) or borderline/malignant tumors (80%). Results: No local or distant recurrences were observed during a median follow-up of 5.5 years. Acute skin toxicity occurred in all patients, with 35% reporting grade 1, 50% grade 2, and 15% grade 3. One patient developed grade 2 fibrosis. Analysis revealed no significant correlations between the severity of toxicity and tumor size, surgical approach, or radiation planning.
This is the retrospective analysis of patients of PMES treated across two institutes of Tata Memorial Centre, Mumbai from 2008 to 2024 as a part of the INSTINCT Study (Ewing’s Sarcoma with intradural involvement- An Ambispective Study). The diagnosis of PMES – meningeal origin (radiological characteristics + intra- operative assessment) and histological confirmation, was ratified in a multi-disciplinary tumor board. All patients were radiologically evaluated with local MR + spine screening and PET-CT. Localized PMES was treated with Ewing’s sarcoma chemotherapy regimen (VAC/IE based) and focal radiotherapy (RT), while CNS disseminated PMES was treated with similar chemotherapy and CSI. Results: Forty-three patients were eligiblefor the study with a median age of 21 years (IQR:13-28) and 25 patients were male. Majority (76.7%, 33 patients) of the cohort had PMES of the spinal region (thoracolumbar - 18). All patients underwent debulking surgery. MRI spine screening and PET-CT was performed in 55.8% and 81.4% of patients. Three patients (6.9%) had CNS dissemination at presentation, while no patients had any systemic metastases Six patients (who were paraplegic at presentation and did not have any clinical improvement after surgery) defaulted after surgery, while two patients succumbed on induction chemotherapy and two patients progressed after induction chemotherapy. Definitive RT was focal in all patients except one patient with CNS dissemination. Survival outcomes were reported on 33 patients who completed treatment. Fifteen patients (45%) had a disease relapse of which the major pattern was CNS dissemination in nine patients followed by local relapse in three and combined relapse in another three. At time of analysis, 20 patients were alive with no evidence of disease, 4 were alive with disease and 9 had succumbed. The 3- year Progression-free survival (PFS) and overall survival (OS) was 58.8% and 75.4%. Conclusion: MR spine imaging has incremental value over PET-CT in PMES metastatic workup. As CNS dissemination was seen in a significant proportion at relapse of PMES, the role of CSI at presentation should be investigated in this rare tumor. Keywords: Ewing's sarcoma, cranio-spinal irradiation
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