TREATMENT MODALITIES FOR ADVANCED METASTATIC VIPOMA

A CASE REPORT

Abstract

INTRODUCTION
Pancreatic neuroendocrine tumors (pNET) secreting vasoactive intestinal peptide (VIP) are rare tumors, with an annual incidence of 1 per 10 million individuals. The diagnosis is made based on a combination of laboratory evaluation (serum VIP level), imaging findings [functional positron emission tomography-computed tomography (PET-CT)] and histological analysis. The first line of treatment is still surgical excision in benign and nonmetastatic disease. However, there is no accepted standard management for patients with metastatic disease, which is seen in 60 to 80% of cases.

METHODOLOGY
We present a case that highlights the challenges in managing metastatic unresectable VIPoma. This is also the first case report in Malaysia using peptide receptor radionuclide therapy (PRRT) as the treatment for metastatic unresectable VIPoma.

RESULTS
We present a case of 62-year-old Chinese gentleman who presented with chronic diarrhoea since 2014. Initial investigation revealed a pancreatic mass at the tail of the pancreas measuring 6.5 cm x 5.2 cm. He underwent distal pancreatectomy and splenectomy. Histopathology report showed a grade 1 pNET with a Ki67 index of <2% and negative margins. He remained asymptomatic postsurgery until 2017, when surveillance CT scan showed a local recurrence at the body of pancreas measuring 2.0 cm x 2.2 cm with multicentric liver lesions, the largest of which measured 4.5 cm x 3.1 cm in segment VIII and 3.6. cm x 3.9 cm in segment IVa. Trans-arterial hepatic chemoembolization was deemed unsuitable. Since March 2018, the patient had multiple hospitalisations for profuse watery diarrhoea, severe electrolyte imbalance and metabolic acidosis. A trial of short-acting Sandostatin was able to alleviate the symptoms temporarily. He was then started on Octreotide LAR 30 mg every 4 weeks, which dramatically improved his diarrhoea. Unfortunately, the effect of Octreotide LAR was transient. In view of refractory diarrhoea despite the combination of shortand long-acting somatostatin analogues, systemic therapy via PRRT was started in October 2018.

CONCLUSION
PRRT offers a step-change in the therapeutic options for functioning pancreatic neuroendocrine tumour. However, data on the efficacy of this treatment on individual functional pNET secreting VIP is still lacking