LAnreotide in Metastatic Pheochromocytoma / PARAganglioma (LAMPARA)

The objectives of this study are: * To assess the efficacy of lanreotide given every 4 weeks in participants with advanced or metastatic paraganglioma/ pheochromocytoma. * To assess the toxicity and safety of lanreotide in participants with advanced or metastatic paraganglioma/ pheochromocytoma. * To document the effects of lanreotide on markers of biochemical activity in participants with advanced or metastatic paraganglioma/ pheochromocytoma. Primary endpoints: • Assess efficacy by estimating the tumor growth rate while a patient is enrolled on study and comparing the growth rates on lanreotide to the pre-enrolment growth rate. Secondary endpoints include measurement of: * Overall survival (OS) * Progression-free survival (PFS) * Overall response rate (ORR) according to RECIST defined as partial response (PR) + complete response (CR) * Magnitude of reduction in levels of 24-hour urinary metanephrines, catecholamines and magnitude of reduction in serum chromogranin A, evaluated every two months while enrolled on study.