Enrico Martin

73 Treatment and survival in pediatric MPNST Methods Data Source Data were obtained from the nationwide Netherlands Cancer Registry (NCR), which is managed by the Netherlands Comprehensive Cancer Organisation (IKNL). The NCR is a population-based registry that gets notified of all newly diagnosed malignancies in the Netherlands by automated pathological archive (PALGA) and the National Registry of Hospital Discharge Diagnosis (LMR). Patient and tumor characteristics and initial treatment information are routinely extracted from medical records. Their quality is high due to thorough training of the registration team and computerized consistency checks at both regional and national levels. Full pathological reports were also requested from PALGA. 22 Cases were matched to PALGA by means of a trusted third party. Malignant peripheral nerve sheath tumors (ICD-O-3: 9540, 9560, 9561) from any site were obtained. Cases from the NCR were obtained from 1989-2017. The data requested was approved by the scientific and privacy committees of IKNL. Covariates Covariates extracted for analysis were: year of diagnosis (1989-2005/2006-2017), sex, age (pediatric ≤18 years vs. adult >18 years), NF1 status, tumor site, tumor stage (metastasis/no metastasis at diagnosis), tumor size (≤5/>5cm), tumor depth (superficial/ deep to the fascia), tumor morphology, resection margin (R0/R1/R2/biopsy only), other treatment modalities, and sequence of treatment. A cut-off between 2005 and 2006 was chosen because of the publication of the Italian and German Soft Tissue Sarcoma Cooperative Group in 2005 showing highest treatment effect of doxorubicin and ifosfamide regimens. 6 NF1 status was extracted based on pathology reports. The diagnosis was concluded either when explicitly reported in the pathological reports or whenever a pathology reports existed of previous plexiform neurofibroma resections or two or more neurofibromas. Tumor sites were recoded into: head and neck, extremities, trunk (including thorax, abdomen, and pelvis), retroperitoneal, and not otherwise specified (NOS). Resection margins were classified as tumor-free (R0), microscopically positive (R1, less than 1mm margins), and macroscopically positive (R2). Tumor grade was not obtained as it is not registered in the NCR and pathological reports inconsistently report it. Vital status and date of death are routinely obtained from municipal demographic registries in the Netherlands. Statistical analysis All pathological reports of a patient registered in the NCR were screened for the final diagnosis of MPNST; all cases with doubtful diagnoses were excluded. Demographical differences were compared between adult and pediatric MPNSTs and in pediatric patients between NF1 and non-NF1 MPNST. Treatment modalities were compared between NF1 and non-NF1 pediatric patients excluding those who presented with metastatic disease. 5-year survival rates were estimated using the Kaplan-Meier 4