Enrico Martin

281 General discussion and future perspectives How oncological and functional outcomes in MPNST could be balanced Preservation of function As oncological MPNST treatment generally follows STS guidelines, we have observed a tendency to resect all MPNSTs with wide margins. Chapter 10 showed us that surgeons are well aware of the functional deficits caused by such an approach and some feel the need that functional status should be taken into account preoperatively. Nevertheless, both Chapter 10 and literature reviews Chapter 8 and 9 show that the reconstruction of lost function in MPNST and other extremity STS are rarely performed. Previously, few studies have been published on functional status after resection of MPNSTs. One study reported a 30% prevalence motor deficits, 23 which is almost in line with the 37% prevalence reported by surgeons in Chapter 10. Another study of 33 extremity MPNSTs, reported 21/33 MPNSTs arising from major nerves, of which 8 underwent complete nerve excision and 8 an amputation. 24 Chapter 11 indeed proved that serious functional deficits are common after MPNST resections, including both motor and critical sensory deficits. Ideally, preventing functional deficits should initially be preferred over reconstruction. As stated earlier, R1 resections have not been associated with impaired survival in any MPNST. 1,3,21 Safety of planned close margin surgery also implies that epineural dissection can be performed in any MPNST. Whenever the MPNST does not encompass more than 50-75% of a nerve’s circumference, epineural dissection could be considered, thus preserving nerve function. 25,26 This technique is important in brachial and lumbosacral plexus tumors as the resection of more nerves decreases function further and limits reconstructive options. Nerve tissue preservation is also important in sciatic nerve tumors. As observed in Chapter 9, sciatic nerve defects are difficult to restore and rarely result in motor function recovery when nerve reconstructions are performed. Moreover, low-grade MPNSTs are known have a very low rate of local recurrences and rarely metastasize even when performing R1 resections. 27 Likewise, benign atypical neurofibromas rarely recur after marginal resections. 27,28 The ability to reliably distinguish both these tumors from high-grade MPNSTs may therefore result in less aggressive surgical treatment overall. As suggested before based on Chapter 6 , a new diagnostic algorithm would help in identifying patients at risk of malignant transformation based on imaging. Concurrently, for certain benign tumors the need for possibly harmful biopsies could be obviated and those requiring resection could be performed directly. Uncertain tumors, those exhibiting insufficient characteristics for high-risk or benign characterization, would still require biopsies. One could advocate that if the resulting biopsy is benign in a symptomatic lesion, a marginal resection should definitely be performed further reducing unnecessary morbidity. Reconstruction of function loss Still, many MPNSTs will require the complete resection of their originating nerve leading to serious morbidity. Fortunately, Chapter 11 as well as Chapter 8 and 9 show us 12