Hi and welcome to HCM.
The next course should be surgical procedure again if tumor is localized. Surgery, if feasible, is the only curative therapy. Symptoms can be treated by octreotide
but this is just symptomatic therapy. It is neuroendocrine tumor
and are considered as malignant but not as much as adenocarcinomas. Also it can but rarely metastase.
Wish you good health.