Chronic Use of Long-Acting Somatostatin Analogues (SSAs) and Exocrine Pancreatic Insufficiency (EPI) in Patients with Gastroenteropancreatic Neuroendocrine Tumors (GEP-NETs): An Under-recognized Adverse Effect.

Background: Somatostatin Analogues (SSAs) are used to treat Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and acromegaly. Side effects of SAAs usually include biliary disorders, gastrointestinal disorders, injection-site pain and hyperglycemia. Exocrine Pancreatic Insufficiency (EPI) is often misdiagnosed as disease progression or failure to SAAs or diagnosed after a delay in patients receiving SAAs. We present our experience with EPI developing in patients following use of SAAs. Methods: We reviewed chart and pharmacy records of 110 GEP-NETs patients who received SSAs. Data was collected including demographics, pathology, stage, dose/duration of long and short-acting SA, use of antidiarrheal, pancreatic enzyme replacement (PER), proton pump inhibitors (PPI) or H2 blockers). Laboratory data include chromogranin-A (CgA), urine 5-HIAA and quantitative fecal fat test (QFFT) or fecal elastase test (FE). EPI was defined by a FE below normal level OR by a reduction of ≥ 21.2% or steatorrhea on QFFT. Patients who were identified to develop EPI were treated with pancreatic exocrine replacement therapy (PERT). Results: Among, 110 GEP-NETs patients, 104 received LA Octreotide and 6 Somatuline Depot Injection. Of these, 23 received short-acting SSA for worsening diarrhea, 96 had intensification of antidiarrheal and 1 got telotristat ethyl. QFFT confirmed EPI in 19, 11 based on clinical symptoms, and 16 had sample error or refusal to collect specimen. CTCAE 4.0 grades of EPI were: grade 2(69%), grade 3(22%) and grade 4(9%). Median time to development of EPI was 12 months (95%CI 3 - 23). Except 1, all patients received PERT either with concomitant PPI (13) or later if no improvement with PERT (6) and 2 on H2 blockers. 37% of the patients had improvement in EPI within 4-8 weeks. Deficiency of vitamins and trace elements was found in 11 of 19 patients, who received supplementation. Conclusions: Our experience constitutes the first and the largest study addressing EPI as a rare but serious complication of chronic use of SAAs. Although SAAs are used to treat diarrhea, paradoxically they can worsen diarrhea secondary to EPI. Early recognition and diagnosis of this under-diagnosed and under-reported side effect of SAAs, such as EPI, can improve not only diarrhea and weight loss in these patients but also can reduce cost of using short-acting SAAs and antidiarrheal.