SDHB mutation status and tumor size but not tumor grade are important predictors of clinical outcome in pheochromocytoma and abdominal paraganglioma

Background. A staging/prognostic system has long been desired to better categorize pheochromocytoma/paraganglioma which can be very aggressive in the setting of SDHB mutations. Methods. A retrospective analysis was conducted of clinical characteristics and outcomes including results of genetic testing, tumor recurrence/metastasis, Ki67/MIB1% staining, and tumor mitotic index in patients with pheochromocytoma/paraganglioma. Results. Patients with SDHB mutation presented at younger age (33.0 years old vs 49.6 years old, P < .001), had increased local recurrence and distant metastases (47.6% vs 9.1 %, P < .001, and 56.3% vs 9.1 %, P < .001, respectively), and lesser median disease-free interval (89.8 months, 95% confidence interval 36.0-96.4 vs not reached, P < .001). SDHB mutation, greatest tumor diameter, and open operative resection were associated with a greater rate of local recurrence and distant metastases (P < .006 each). SDHB mutation and tumor diameter were independent risk factors for local recurrence (P <= .04 each) and metastases. Ki67 % and mitotic index were not associated with SDHB mutation (P >= .09 each), local recurrence (P = .48, P = .066, respectively), metastases (P >= .22 each), or disease-free interval (P >= .19 each). Conclusion. SDHB status and primary tumor size are more predictive of patient outcome than Ki67 % or mitotic index and should be part of any clinically relevant, prognostic scoring system.