Adverse skeletal related events in patients with bone-metastatic pheochromocytoma/paraganglioma

Metastatic pheochromocytomas and paragangliomas (PPGLs) are frequently associated with skeletal complications. Primary objective: to describe the frequency of adverse skeletal related events (SREs) in PPGL patients with bone metastases (BMs). Secondary objectives: to 1) identify predictive and prognostic factors for SREs and 2) obtain information on the effectiveness of bone resorption inhibitors in reducing SRE risk and improving outcomes in term of survival and SREs time onset. In this retrospective multicenter, multinational study, 294 PPGL patients were enrolled. SREs occurred in 90 patients (31 %). Fifty-five patients (19 %) had bone fractures, 47 (16 %) had spinal cord compression, and 11 (4 %) had hypercalcemia. Twenty-two patients (7 %) had more than one SRE. Sixty-four patients (22 %) underwent surgery, and 136 (46 %) underwent radiotherapy. SREs occurred a median of 4.4 months after diagnosis of BM (range, 0-246.6 months). Independent factors associated with reduced risk of SREs in multivariable analysis were I-131-MIBG radionuclide therapy (hazard ratio [HR], 0.536 [95 % CI, 0.309-0.932]; P = .027) and absence of liver metastases (HR, 0.638 [95 % CI, 0.410-0.992]; P = .046). The median overall survival duration was 5.3 year. In multivariable analysis, age younger than 48 years at PPGL diagnosis (HR, 0.558 [95 % CI, 0.3877-0.806]; P = .002), absence of liver metastases (HR, 0.618 [95 % CI, 0.396-0.965]; P = .034), treatment with bisphosphonates or denosumab (HR, 0.598 [95 % CI, 0.405-0.884]; P = .010), and MIBG radionuclide therapy (HR, 0.444 [95 % CI, 0.274-0.718]; P = .001) were associated with a reduced risk of death. SREs occur frequently and early in bone-metastatic PPGL patients but do not negatively impact survival. MIBG radionuclide therapy and treatment with bone resorption inhibitors are associated with favorable outcome.