Methods of reducing the likelihood of carcinoid heart disease in patients with neuroendocrine tumors

A method of treating or managing a human patient with a newly diagnosed neuroendocrine tumor, wherein the human patient with the newly diagnosed neuroendocrine tumor has not been diagnosed with carcinoid syndrome or carcinoid heart disease, comprising

• at least quarterly, after newly diagnosing the neuroendocrine tumor, measuring a level of 5-hydroxyindoleacetic acid (5-HIAA) in a plasma or urine sample from the patient, and
• daily administering a therapeutically effective amount of telotristat ethyl or a pharmaceutically acceptable salt thereof to a patient having an initial level of 5-HIAA at least two times greater than the upper limit of normal (ULN), wherein the initial level of 5-HIAA is a level prior to administration of telotristat ethyl,
• wherein the ULN is about 22 ng/ml for the plasma sample or 8 mg/24 hours for the urine sample, and
• wherein administering telotristat ethyl or the pharmaceutically acceptable salt thereof to the patient delays or reduces the likelihood of the development of carcinoid heart disease in the patient.