Purpose: The WHO classification for well-differentiated pancreatic endocrine neoplasms (PENs) incorporates both stage and grade. This study compares the prognostic value of a simplified staging and grading system with the WHO system in a large single-institution study.
Patients and methods: A prospective database (1982 to 2005) identified 183 patients who underwent operative treatment for PENs. Tumors were staged (< 2 cm primary, >/= 2 cm primary, or metastases) and graded (low grade: no necrosis and < two mitoses/50 high-powered fields [HPF]; or intermediate grade: necrosis and/or >/= two mitoses/50 HPF) with a simplified schema. Influence of stage and grade on recurrence and disease-specific survival (DSS) was determined. Prognostic strength was assessed with the concordance index (CI).
Results: Median age of the 183 patients was 56 years, and 53% were women. Median follow-up time was 44 months (range, 1 to 226 months). Classification identified 28 patients (15%) with WHO 1.1 disease, 74 (41%) with 1.2 disease, and 81 (44%) with 2.0 disease. Classification by stage identified 35 patients (19%) with tumors less than 2 cm, 96 (52%) with tumors >/= 2 cm, and 52 (29%) with nodal or distant metastases. Tumors were low grade in 102 patients (56%). Earlier stage tumors were more likely to be low grade (< 2 cm, 83%; >/= 2 cm, 61%; metastases, 28%; P < .001). The WHO classification, tumor stage, and grade were associated with 5-year DSS (P < .001). Tumors >/= 2 cm or metastases are stratified by grade (5-year DSS rate for low v intermediate grade: >/= 2 cm, 97% v 80%, respectively; P < .001; metastases, 93% v 62%, respectively; P = .05). The CI was 0.72 for WHO, 0.71 for stage, 0.66 for grade, and 0.76 for stage combined with grade.
Conclusion: Accurate prognostic information can be obtained by combining tumor size and metastases with simple grading information based on necrosis and mitotic rate.