Enrico Martin

55 Treatment and survival in the Netherlands Figure 1 Relative age distribution of neurofibromatosis type 1 (NF1) and sporadic patients Treatment of localized adult MPNST Surgical resection was performed in 88% of localized MPNSTs ( Table 2 ). Surgical margin involvement did not differ significantly between retroperitoneal and non- retroperitoneal tumors (p>0.05). Overall, a microscopically radical resection (R0) was achieved in 66.3% of the patients, while R1 and R2 resections were present in 27.5% and 6.1% respectively. Overall, additional radiotherapy was administered in 44.2% of the patients and less frequently in patients with a retroperitoneal MPNST (29.6%, p<0.05). Postoperative administration was more common than preoperative administration of radiotherapy (88.4%), but overall, postoperative radiotherapy use was not more common after R1 resections (42.5%) compared to R0 (39.9%, p>0.05). Preoperative use of radiotherapy is becoming more common at the end of the study period; in patients receiving radiotherapy after 2006, preoperative administration was performed in 22.7%. In surgically treated patients, chemotherapy was more commonly administered in retroperitoneal MPNST (18.5% vs. 6.1%, p<0.05). In patients who were not operated, radiotherapy and chemotherapy were administered in 33.3% and 24.0% of the patients respectively. No differences were present between non-retroperitoneal and retroperitoneal MPNST (both p>0.05). 3