Enrico Martin

63 Treatment and survival in the Netherlands decrease morbidity. This is of special interest for tumors situated in extremities and the retroperitoneum. To date, no rationale has yet been proven for treating MPNSTs differently from other STS when using chemotherapy. 15 In localized disease there may be a role for neoadjuvant chemotherapy in high-risk MPNSTs. 15,16 In individual cases neoadjuvant administration of chemotherapy may help initially deemed irresectable tumors to become resectable. 22,29 As retroperitoneal STS are more difficult to treat because of their relation to critical organs and structures, only recently guidelines have stated macroscopically complete resections to be necessary and just. 30 This study also supports the survival benefit of such resections. Neither radiotherapy nor chemotherapy has yet shown a significant benefit for survival in retroperitoneal STS. 31–33 Several ongoing trials are currently however still investigating the exact role of chemotherapy in retroperitoneal STS. 34 As retroperitoneal MPNSTs have one of the highest risks for local and distant recurrence and early death, the additional value of multimodal treatment is especially of interest in these patients. 35,36 Strengths and limitations Limitations are inevitable as in part only registry data was available. As NF1 status is not routinely registered in the NCR, the total amount of NF1 patients is possibly underestimated. However, the incidence rate in this study is in concordance to other series. 3–5,10 Furthermore, tumor grade could not be analyzed because of heterogeneity in reporting. However, the definition of low-grade tumors has only recently been assessed in a consensus meeting. 37 Unfortunately, local recurrence and distal metastasis rates were not recorded either, hindering further analyses for the role of multimodal treatment in localized MPNST. Nevertheless, this study is to the authors’ knowledge the first nationwide study on MPNSTs. This design makes the data and models more generalizable as there is no form of selection or referral bias. As such, a model for a relatively homogenous group of localized adult non-retroperitoneal MPNSTs could be constructed specifically. The SEER database also allows for analyses of large patient cohorts, but lacks data on NF1 status, tumors within neurofibromas, R0/R1/R2 resection margins, the use of chemotherapy, and pathology review. 24 As STS patients present as a very heterogeneous group of patients, research on a single histological subtype level is necessary to aid in tailoring ideal treatment and outcomes and to increase our knowledge of their behavior. Especially as there may be important clinical variety within a single entity such as in MPNSTs, like NF1 patients, malignant transformation within neurofibromas, or tumors associated with large nerve bundles such as the brachial and sacral plexus. However, complete excision is necessary in all of these patients, yet R1 resections may suffice in order to preserve functionality, as MPNSTs have reported rates of motor deficits in over 30%. 38 Further understanding of ideal patient-tailored approaches in rare STS such as MPNSTs can only be made possible by large international collaborations including all medical specialties involved in their multimodal treatment. 3