Intercontinental collaborative experience with abdominal, retroperitoneal and pelvic schwannomas

Background Schwannomas are rare tumours that pose a significant management challenge in the abdomen, retroperitoneum and pelvis. No data are available to inform management strategy. Methods A collaborative international cohort study, across specialist sarcoma units, was conducted to include adults presenting between 2000 and 2017 with histopathologically confirmed schwannomas within the abdomen, retroperitoneum or pelvis. Results Of 485 patients across 12 centres, 38 (7 center dot 8 per cent) were discharged without follow-up, 199 (41 center dot 0 per cent) underwent early resection and 248 (51 center dot 1 per cent) had radiological monitoring. Of these 248 patients, 96 (38 center dot 7 per cent) eventually had surgery, giving an overall resection rate of 60 center dot 8 per cent (295 of 485). At baseline, median tumour volume was 90 center dot 1 (i.q.r. 26 center dot 5-262 center dot 0) cm(3). The estimated growth rate was 10 center dot 5 (95 per cent c.i. 9 center dot 4 to 11 center dot 6) per cent per year, and was consistent in the short term (within 2 years of diagnosis) and long term (beyond 2 years) (rho = 0 center dot 405, P = 0 center dot 021). A decision to operate was more common in symptomatic patients (P < 0 center dot 001) and for rapidly growing tumours (growth rate more than 20 per cent per year) (P = 0 center dot 025). R0/R1 resection was achieved in 91 center dot 6 per cent of patients (263 of 287). Kaplan-Meier long-term recurrence rates after R0/R1 resection were 2 center dot 3 and 6 center dot 7 per cent at 3 and 5 years respectively. Conclusion Specific recommendations include: indications for early surgery, prediction of growth from radiological monitoring, promotion of selective submacroscopic resection and cessation of postoperative imaging surveillance.