574P Clinical impact of the GAPP score and SDHB negativity in patients with pheochromocytoma/paraganglioma

Abstract

Background: Pheochromocytoma (PCC) and paraganglioma (PGL) are rare tumors occurring in the adrenal medulla and extra-adrenal tissues, respectively. The clinicopathological features have not been fully elucidated, especially in Asian cohorts. Methods:We retrospectively reviewed 65 patients with PCC/PGL between 1983 and 2020. Patient characteristics and clinical outcomes (overall survival [OS] and relapsefree survival [RFS]) were analyzed based on the medical records. Morphological assessment and immunostaining of Ki-67 and succinate dehydrogenase complex subunit B (SDHB) were performed in the available specimens. Subsequently, the influence of the grading system for pheochromocytoma and paraganglioma (GAPP) score and SDHB negativity on the clinical outcomes was evaluated.Results: The median age of the patients was 51 years, and PGL accounted for 69% of the cases. Initial stage was localized disease in 83% of the patients, and the major primary lesions were in the adrenal gland (31%), retroperitoneum (24%), and bladder (15%). Fifty-three patients with localized disease underwent curative resection, and six and two patients with metastatic disease underwent surgery and chemotherapy, respectively. Morphologically, the GAPP score was 0-2 (low-risk) in nine, 3-6 (intermediate-risk) in 33, and 7-10 (high-risk) in three specimens. SDHB immunostaining was performed in 41 specimens, and the negativity rate was 19%. The 3-year OS rate in all 65 patients was 95%, and was significantly better in patients with localized than metastatic disease (3-year OS 98% vs. 80%, P ¼ 0.008). The 3-year RFS rate in the 53 patients with localized disease was 87%. The rate was significantly different among patients in the low-risk, intermediate-risk, and high-risk groups (3-year rate 100% vs. 96% vs. 33%, P < 0.0001), and between those in the SDHB-positive and SDHBnegative groups (3-year rate 100% vs. 57%, P ¼ 0.03).Conclusions: While the general outcome of PCC/PGL was favorable, our analysis suggested that high-risk GAPP score and SDHB negativity were predictors of subsequent relapse in patients with localized disease who underwent resection. The correlation between lack of SDHB expression and SDH-related mutations should be assessed in future studies.Legal entity responsible for the study: The authors.