ESTRO 2022 - Abstract Book

S143

Abstract book

ESTRO 2022

Conclusion We demonstrated the potential clinical benefit of reduced neurocognitive impairment based on robustly optimized HS IMPT plans, with marginal effect to target coverage and thereby estimated tumor control. Our results suggest that any dose reduction to the hippocampus could have valuable impact in terms of cognitive function for pediatric patients treated with CSI.

PD-0166 Nasopharyngeal Carcinoma in Children and Adolescents: Result of Patients Treated with 61,2-63 Gy

M. Da ğ delen 1 , S. Kanat 1 , T. Kurt Çatal 1 , H. Yıldırm 1 , E. Sedef Akovalı 2 , S. Çavdar Karaçam 1 , Ö. Uzel 1

1 Istanbul University- Cerrahpasa, Cerrahpasa Medical Faculty, Department of Radiation Oncology, Istanbul, Turkey; 2 Istanbul University- Cerrahpasa, Cerrahpasa Medical Faculty, Department of Radiation Oncology,, Istanbul, Turkey Purpose or Objective Nasopharyngeal Carcinoma (NPC) in childhood was seen rarely; the incidence rate was less than 1% among all childhood tumors. Although treatment was similar, tumor control (LC) and overall survival (OS) rates were better when compared with adults’ NPC. However, the toxicities were observed more frequently than adults. In this study; we retrospectively reported results in adolescence and childhood NPC patients previously treated with 61,2-63 Gy intensity modulated radiation therapy ( IMRT). Materials and Methods Between 2010-2020, 14 patients were included in our study. The median age was 16 and the female/ male ratio was 3:11. The primary tumor stage was T4 in 42,9%, and the nodal stage was N2 in 71,4%. TPF (Docetaxel-5FU-Cisplatin) was given for induction chemotherapy (ICT) before 2019 whereas GP (Gemcitabine-Cisplatin) was given for ICT after 2019. Twelve patients received ICT (TPF or GP) before chemoradiotherapy (10patients) or radiotherapy (2 patients), 2 patients were treated with only chemoradiotherapy. PTV 61,2 (complete or good partial response) -63Gy (partial response) included the primary tumor and metastatic lymph node for high-risk volume. PTV 54Gy included both the whole nasopharynx and whole involved nodal level. For low-risk volume; PTV 45Gy was covered high-risk regions and elective bilateral cervical lymph nodes. Survival analyses were made by Kaplan-Meier method. Results The median follow-up time was 80,5months (range:7-139). All patients had complete responses after chemoradiotherapy. The 5-year locoregional controls (LRC), disease-free survival (DFS), and OS were 100%. One patient developed distant metastasis (bone) 62 months after treatment. Grade 3 acute side effects were observed as mucositis 14%, dysphagia 14%, dermatitis 21%. There were no grade 4 acute side effects. Chronic side effects; there were grade 2 xerostomia in 50% and hearing impairment in 28%. Fibrosis was observed in only one patient, while hypopituitarism was observed in one patient. Radiation-induced trismus, cranial nerve palsy, aspiration, and alopecia were not observed. Conclusion Using the IMRT technique with dose reduction was compared with the historical series. Although lower dose radiotherapy was administered, local-regional control was higher and the rate of side effects was lower in our study. Prospective multicenter studies are needed for further dose reduction, especially in patients with complete response after induction chemotherapy. 1 The Christie NHS foundation Trust, Clinical Oncology, MANCHESTER, United Kingdom; 2 The Christie NHS foundation Trust, Radiotherapy Physics, MANCHESTER, United Kingdom Purpose or Objective To report acute and early late toxicities and early clinical outcomes following proton beam therapy (PBT) for paediatric/adolescent head and neck (HN) malignancies treated at our institute. Materials and Methods We retrospectively analysed prospectively maintained electronic records for all patients <25 years of age treated with PBT at our institute for HN malignancies between 2018-2020. All patients were treated with pencil beam scanning PBT with daily cone-beam CT (CBCT). Toxicity was assessed weekly on treatment and then at regular follow-up and graded according to CTCAE v5. All patients had post-treatment imaging to assess response at 12 weeks and repeat imaging was performed in those with suspicion of clinical recurrence. Results 48 patients <25 years of age were treated with PBT at our institute for HN malignancies during the study period. The median age at treatment was 14 years (range: 1-25 years). Patient, disease, and treatment characteristics are highlighted in table 1. After a median follow-up of 18 months (Range: 8-34 months), the actuarial 1-year overall survival, local control, and distant control rates for the entire cohort were 92%, 89%, and 94%, respectively. Five patients experienced an isolated local failure (3 RMS, 1 ES, and 1 other). Only 1 patient had a nodal recurrence and was surgically salvaged. Isolated distant failure PD-0167 Acute, late toxicities & early outcomes in children after proton therapy for head & neck malignancy A. Pilar 1 , D. Saunders 1 , S. Pan 1 , S. Gaito 1 , F. Charlwood 2 , M. Lowe 2 , E. Smith 1 , A. Mcpartlin 1 , N. Thorp 1