Background: Factors associated with rectal NENs prognosis are poorly investigated. Aim: To evaluate the prognostic role of the ENETs staging and grading systems in rectal NENs. Methods: Tertiary referral, multicenter, retrospective study. Factors associated with OS and PFS were investigated by Cox-regression analysis, with best size cut-offs calculated by ROC analysis. Results: Of 100 patients (mean age 55, 45% male, mean size 16.2 mm) 62, 5, 10 and 23 were TNM stage 1 to 4, and 63, 15 and 22 were G1, G2 and G3. Primary treatment was endoscopic snare resection in 62%, endoscopic mucosal resection/endoscopic submucosal dissection in 10%, surgery in 20% and medical treatment in 8%. The best size cut-offs to predict OS and PFS were 10 and 12 mm. During a mean follow-up of 40.7 months 12% died and 26% progressed. The 5-year OS and PFS were 79.5% and 65.2%. Stage IV and G3 were associated with worse OS (HR 8.16; p = 0.002; HR 15.57; p = 0.0004) and PFS (HR 14.26 p < 0.0001; HR 6.42; p = 0.0007). Conclusion: Both staging and grading accurately predict rectal NENs prognosis. Size alone has limited accuracy as 26% of patients with stage IV and 16% with G3 have a primary tumour≤10 mm.
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