Dr Riechelmann on the Management of Refractory Carcinoid Syndrome in Functional GI NETs

"It's important for clinicians to evaluate the aggressiveness of the disease and to evaluate patients with small bowel NETs for the secretion of serotonin. It's important to screen these patients with a 24-hour urinary 5-HIAA [test], and if it is elevated, then that patients has to continue with a somatostatin analogue."

Rachel Riechelmann, MD, PhD, head of the Gastrointestinal Oncology Division at the A.C. Camargo Cancer Center in São Paulo, Brazil, shared key clinical guidance for the management of refractory carcinoid syndrome in patients with functional gastrointestinal (GI) neuroendocrine tumors (NETs).

Carcinoid syndrome is a collection of symptoms that could be encountered by patients with GI NETs. Somatostatin analogs are a standard treatment option for these patients; however, treatment standards for refractorycarcinoid syndrome are not as clear.

During the 2025 ESMO Gastrointestinal Cancers Congress, Riechelmann emphasized the importance of assessing serotonin secretion in patients with small bowel NETs, noting that all patients should undergo screening via a 24-hour urinary 5-hydroxyindoleacetic acid (5-HIAA) test. Detection of elevated 5-HIAA confirms the presence of a hormonally functional tumor and guides the initiation and continuation of symptom-directed therapy.

According to Riechelmann, patients who demonstrate serotonin hypersecretion should begin treatment with a somatostatin analog and remain on this therapy indefinitely, given the chronic nature of carcinoid syndrome and the ongoing risk of symptom recurrence and carcinoid-related complications.

Riechelmann noted that disease aggressiveness, tumor burden, and associated complications should guide subsequent treatment sequencing following somatostatin analog initiation. These clinical parameters help determine when to escalate therapy and which systemic options to consider, including peptide receptor radionuclide therapy (PRRT), everolimus, or cytotoxic chemotherapy in select patients.