Enrico Martin

37 Treatment and survival differences across tumor sites survival of the 141 primary intracranial MPNSTs presented in this paper seems to be better than currently suggested in the literature. This difference could be the result of different grades of tumors included, treatment modalities used, and extent of resection achieved. On the other hand, lymphatic metastases have not been reported in intracranial MPNSTs, which may be associated with improved prognosis for this site of origin. 29,30 It is assumed that metastases from intracranial MPNSTs mainly occur as a consequence of cerebrospinal fluid dissemination that result in drop metastases. 29 Head & Neck MPNST MPNSTs arising from extracranial head and neck sites have previously been associated with a worse prognosis, but this rarely reached statistical significance, mainly due to small population sizes. 10,11,14,32 This is in line with findings of this study suggesting that they have worse survival compared to limb and intracranial sites. 5-year survival rates have been reported to vary from 20% to 47%. 14,32–34 Unlike intracranial MPNSTs, these tumors have been reported to metastasize to lymph nodes, but also to lungs. 34,35 Spinal MPNST Reports about spinal MPNSTs are as rare as those about intracranial tumors. Small case series have shown that survival in spinal tumors is generally unfavorable. 20,36–38 Reported 5-year survival rates vary from 16% to 44%. 20,37,38 Generally, MPNSTs of spinal origin are considered difficult to resect completely, because of close vital structures adjacent to the tumor site. 20,37,38 Although radiotherapy is recommended for local control in spinal MPNSTs, it has not been shown to have an effect on survival. 36,37 Likewise, this study did not find an additional benefit for radiotherapy in spinal tumors. Radiotherapy as a monotherapy was significantly associated with worse overall survival independent of tumor and patient specific characteristics. Since large amounts of radiation may induce myelopathy, 37,39 tumor control using radiotherapy must be executed in cases where tumor invasiveness causes symptoms. Core MPNST Core tumors are among the most frequent MPNSTs; prevalence reported in large series vary from 34-55%. 4,9–11,14,32,40 This is consistent with the SEER data which shows a prevalence of 40%. This location is more frequently affected in NF1 patients compared to sporadic MPNSTs. 4,40 Although generally seen as tumors with a less favorable outcome, only three large institutional studies have previously shown this difference to be significant. 11,14,32 This study supports their findings that core site tumors tend to have a worse prognosis. Extremity MPNST Extremities are also a common tumor site for MPNSTs with a prevalence in large series varying between 35% and 57%. 4,9–11,14,15,32,40 MPNSTs arising from extremities tend to be more easily completely resected compared to other tumor locations. 4,9,11,14,32 Therefore, 2