ESTRO 38 Abstract book

S458 ESTRO 38

Results All pts received the planned TMI dose (95% of PTV received almost 90% of prescription dose) with a good Organ At Risk (OAR) sparing (the dose at OAR was < 50% of prescription dose); all pts, after the transplant, achieved engraftment with no secondary graft failure. No grade 3- 4 extra-hematological toxicity has been registered in the first 30 days. Five deaths have occurred, 2 due to TRM and 3 due to progression disease. With a median follow-up time of 39 months, 3-yr PFS was 38% and 3-yr OS was 48%. Day +100 incidence of grade II-IV aGVHD was 36%; grade III-IV 9%; 1-year incidence of cGVHD was 39%. 3-year relapse incidence was 39%. 7 pts have experienced an extensive/severe cGvHD with significant involvement the lower legs and ankles. This toxicity seems more evident for patients treated with higher doses (>10 Gy), probably correlated also to the skin higher dose delivered with HT technique, in particular at the pretibial level for patients with poor adipose pannicle. The combination effect with the type of cTreoCT and with the type of used GvHD prophylaxis regimen should be better investigated. Conclusion These data show that TMI addition to cTreoCT is feasible and has not demonstrated an addition of at least short- term toxicities. The late toxicity found in the limbs leads us to find solutions to avoid such side effects in patients irradiated at doses above 12 Gy, such as reviewing the PTV contouring at the tibia level or as using different techniques in legs irradiation (like tomodirect) and as improving GvHD prophylaxis regimen. PO-0869 Reducing pulmonary and renal toxicity in children receiving TBI with forward planned IMRT M. Bishr 1 , E. Nicholson 2 , E. Durie 3 , M. Potter 2 , M. Ethell 2 , C. Anthias 2 , C. Messiou 4 , I. Johnson 5 , S. Eagle 3 , W. Ingram 3 , F. Saran 3 , H. Mandeville 5 1 Children's Cancer Hospital Egypt, Department of Radiotherapy, Cairo, Egypt ; 2 Royal Marsden NHS Foundation Trust, Department of Haematology, London, United Kingdom ; 3 Royal Marsden NHS Foundation Trust, Department of Radiotherapy, London, United Kingdom ; 4 Royal Marsden NHS Foundation Trust, Department of Radiology, London, United Kingdom ; 5 Royal Marsden NHS Foundation Trust, Children and Young People's Unit, London, United Kingdom Purpose or Objective Total body irradiation (TBI) is an integral part of conditioning regimens prior to haematopoietic stem cell transplantation (HSCT). However, there is a risk of both short term and long term side effects, especially in children. This study evaluates the pulmonary and renal toxicity of a novel forward planned (FP) intensity modulated radiation therapy (IMRT) TBI technique. Material and Methods We retrospectively identified 65 paediatric patients (≤ 16 years old) who received TBI-based full intensity allogeneic HSCT between July 2009 and March 2018. The whole body was the specified target volume and the dose was prescribed to the 100% with a reduction of the median lung dose by approximately 15% compared to the whole body. All dose modulations were multi-leaf collimator-based and treatment was delivered twice a day using 10 MV photons and a dose rate of 14-19cGy/min. Pulmonary toxicity was subdivided into infective pneumonia (IP), based on the identification of a causative agent in blood or broncho- alveolar lavage, and idiopathic pneumonitis syndrome (IPS) when no organism could be detected. The estimated glomerular filtration rate (eGFR) was calculated using Schwartz’s formula and chronic kidney disease (CKD) was defined as eGFR <60 mL/min/1.73m 2 for ≥ 3 months. Poster: Clinical track: Paediatric tumours

Results All patients were treated for haematopoietic malignancies, most commonly acute lymphoblastic leukemia (78.5%), at a median age of 8.7 years (range 2- 16). TBI doses were 14.4Gy (63%), 13.2Gy (5%) or 12Gy (32%). Patients were followed up for a median of 1.7 years (range 13 days – 8.3 years) and the mean overall survival (OS) was 58 months (95% CI 45.9 – 70). The 2-year OS was 68% (95% CI 54 – 78) and the 2-year progression-free survival (PFS) was 54% (95% CI 40 – 66). The 100 day non- relapse mortality (NRM) in our patients was 14% (95% CI 7 – 23) and 2-year NRM was 23% (95% CI 13 – 35). None of the patients developed CKD at 5 years and a total of 31 patients (47.7%) developed pulmonary toxicity. Only one patient (1.5%) developed grade 1 IPS, while 30 patients (46.2%) had IP, of whom five patients died accounting for 41.6% of NRM. One patient developed bronchiolitis obliterans organizing pneumonia (BOOP) 4 months post- HSCT and another patient developed pulmonary inflammatory myofibroblastic tumor 6.4 years post-HSCT. Compared to males, females had a lower risk of developing pulmonary toxicity (OR 0.25, p-vale 0.037). Patients who were cytomegalovirus (CMV)-mismatched from their donors exhibited 3.4-times higher risk of developing pulmonary toxicity as compared to CMV- matched recipients with a trend for significance (p-value 0.08). Conclusion Compared to parallel opposed technique in literature, our novel FP-IMRT-TBI technique for paediatric full intensity HSCT yields lower rates of renal and pulmonary toxicity, specifically IPS. This favourable safety profile supports the adoption of highly conformal radiotherapy techniques to further improve quality of life of long-term survivors after HSCT in childhood. PO-0870 Treatment Outcomes for Pediatric Basal Ganglia Germinomas: A single institute experience in Taiwan Y. K ang 1 , S. Lin 2 , Y. Lee 3 , F. Chang 4 , M. Liang 3 , H. Chen 3 , Y. Liu 1 , T. Wong 3 , Y. Chen 1 1 Taipei Veterans General Hospital, Division of Radiation Oncology- Department of Oncology, Taipei, Taiwan ; 2 National Yang-Ming University, Faculty of Medicine, Taipei, Taiwan ; 3 Taipei Veterans General Hospital, Division of Pediatric Neurosurgery- Neurological Institute, Taipei, Taiwan ; 4 Taipei Veterans General Hospital, Department of Radiology, Taipei, Taiwan Purpose or Objective Pediatric basal ganglia germinoma is a rare and unique disease. Our purpose was to evaluate the clinical outcomes of pediatric basal ganglia germinomas after treatment. Material and Methods The medical records of 33 children with pediatric basal ganglia germinomas treated at Taipei Veterans General Hospital between 1994 and 2015 were retrospectively reviewed. There were 1 female (3.03%) and 32 males (96.97%) with a median age at diagnosis of 12.18 years (range, 7-19 years old). Age, sex, symptoms, pathological findings, treatment modalities, recurrence patterns, recurrence date, death date, and toxicities were recorded. Survival curves were estimated with the Kaplan- Meier method, and univariate Cox proportional hazards models were used to identify possible risk factors. Results The median overall survival was 7.77 years (range, 1.76- 24.28 years), with 2- and 3-year disease-free survival rates of 97% and 94%, respectively. Thirty patients (90.9%) were treated successfully without recurrence. Three patients (9.1%) suffered from recurrence during follow up, and all of them were treated successfully by salvage treatment. Only one patient (3.0%) died during follow-up because of radiotherapy related sarcoma over scalp. Focal irradiation