In Argentina, ASR of osteosarcoma is similar to that in high-income countries, but survival is lower in all regions. Future work will focus on identification and reduction of causes of preventable treatment failure.

Background: Information on the epidemiology of pediatric liver tumors in Latin America is limited. Purpose: To describe the incidence of liver tumors in a pediatric registry in Argentina according to geographic region, national trends over 16 years, and survival related to stage, age, sex, and care center. Methods: Newly diagnosed liver tumors cases are registered in the Argentine Pediatric Oncology Hospital Registry (ROHA) with an estimated coverage of 91% of national cases. Age-standardized incidence rate per millon (ASR) was calculated based on the National Vital Statistics Reports. Five-year overall survival (OS) was estimated using the Kaplan-Meier method. The log-rank test was used to compare subgroup survival. Results: Two hundred seven cases of hepatoblastoma (HB) and 73 of hepatocellular carcinoma (HCC) were identified. ASR of liver tumors was 1.8/million (95% confidence Interval [CI], 1.6-2.0) per year. ASR was 1.4 (1.2-1.6) for HB and 0.4 (0.3-0.5) for HCC. For HB, the highest incidence was found in the northwest region including the Altiplano. OS was 60.4% (53.4-66.8) for HB and 36.1% (25.2-47.2) for HCC. Five-year survival rate of children with metastatic HB treated at liver transplant hospitals (LTH) was 54.2% (30.3-73.0) compared to 13.3% (2.2-34.6) for those seen at other hospitals (OH)

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10074 Background: Studies comparing survival between adult and paediatric population with osteosarcoma are scarce and contradictory. Generally adults were excluded from analysis in historical series. End Point: evaluate age as prognostic factor in ostosarcomas IIb treated exclusively by a multidisciplinary group in a single institution. Methods: 132/278 patients with histological diagnosis of osteosarcoma IIb were selected. All were treated exclusively in our hospital from July 1988 until December 2010. Patients 17 years old or younger were considered paediatric. They all received presurgical chemotherapy with the same scheme: ifosfamide + doxorrubicin + high dose methotrexate. Univariate analysis was made (Fischer exact test). Survival was calculated wih Kaplan-Meier actuarial method. Curves were compared with log rank test. Multivariate Cox analysis was made. Results: Median age was 19.6 years (std: 9,1; range 5-58). Adults: 77, children: 55. No differences were detected between the two age groups regarding: elevated alkaline phosphatase, kind of surgery (amputation vs. limb sparing), relapse site (lung, local, other), necrosis greater than 90% or number of lung resections. There was a tendency towards axial localization in adults (p=0.05). No paediatric patient had inadequate medical intervention, but it was present in 14.3% of adults (p=0.002). 5 year Overall survival (5y OS) in children was 85,2% compared with 61,8% in adults (p=0.005); Disease free survival (DFS) had a non significant tendency to be better in children (69.6% vs. 51,3%). Variables associated with worse OS were: axial location (p=0.01), elevated alkaline phosphatase (0.003), amputation (p=0.008), local relapse or systemic non-lung metastasis (p= 0.001), necrosis less than 90% (0.001). Multivariate Cox analysis showed association between OS and paediatric population (p=0.01) and necrosis greater than 90% (p=0.001), while DFS was associated with necrosis greater than 90% (p=0.01) and elevated alkaline phosphatase (p=0.05). Conclusions: Paediatric population presents better survival compared to adults in our institution. Differences in tumour biology and in the mode of presentation related to age may be the explanation.

Background: The GATLA Collaborative Group has a 50 year (y) long experience of running cooperative trials for lymphomas in Argentina. Aim: Describe the outcome of pediatric patients(pts) treated according to the international cooperative work with AHOPCA and St. Jude Children's Research Hospital (11-EHP-12) adopting OEPA/COPDAC strategy for High Risk (HR) pts and ABVD for Intermediate (IR) and Low Risk (LR) pts. Methods: 11-EHP-12: Risk assignment according Stanford/Danna Farber/ SJCRH Consortium classification. LR: ABVD x 4± IFRT (20 Gy). IR: ABVD x 6 ± IFRT (20 Gy). HR: OEPA-COPDAC+IFRT (20/25 Gy). Response evaluation: LR after 4th cycle, IR and HR after the 2nd cycle. Complete Remission (CR): response > 80% reduction and PET negative. Partial Remission (PR): response >50% and <80% reduction and/or PET positive. 170 pediatric patients (pts) were enrolled since November 2012. 133 evaluable pts. 37 on treatment and/or a follow up of less than 5 years. Sex: M/F: 85 (63,9%) /48. Median age: 13 y (range 4-18 y). Histology: nodular sclerosis 91 (68,4%), mixed celularity 31 (23.3%), lymphocyte rich 1 (0,7%), lymphocyte depleted 1 (0,7%), nodular lymphocyte predominant 8 (6,9%). Stage: I :16 (12%), II: 51 (38.4%), III: 27 (20.3%), IV: 39 (29.3%). B Symptoms: 66 (49.6%). Interim evaluation: PET/TC: 109/133 (82%), TC: 24. Distribution by risk groups: HR pts.: 77 (57,9%), IR: 35 (26,3%), LR: 21 (15,8%). Results: 5 y OS was 94% (100% for LR and IR, and 91% HR) and 5y EFS was 88% (100% for LR, 91% IR, and 84% HR). 95% of the LR pts and 72% of the IR pts did not undergo radiotherapy. 70% of the HR pts achieved CR after the 2nd OEPA and received 20 Gy IFRT. According PR or CR after 2nd OEPA, the 5y EFS in HR pts was 84% and 90% respectively. Conclusion: Thanks to this international cooperation We could significantly improve the results in Argentina compared to our previous experience (7-PHD-96: COPP-ABV x 6 + IFRT Bulky disease or PR (20/25Gy): 5yOS:85%, 5yEFS:67%), reduce the number of patients who required radiotherapy and reproduce the Euronet experience for HR pts in a different context. Figure Disclosures No relevant conflicts of interest to declare.