A multi-institutional German research group has shown that the drug octreotide LAR can slow tumor progression in patients with malignant neuroendocrine tumors of the midgut according to research presented at the sixth annual Gastrointestinal Cancer Symposium.

The findings were presented at the sixth annual Gastrointestinal Cancer Symposium, co-sponsored by the American Gastroenterological Association (AGA) Institute, the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO) and the Society of Surgical Oncology (SSO).

Octreotide LAR is a peptide that mimics the hormone somatostatin, which regulates the endocrine system and also affects cell proliferation and neural communication. Other studies have indicated that octreotide LAR may be effective for treating malignant neuroendocrine tumors (NETs), but this is the first placebo-controlled trial to test this therapy.

"While malignant neuroendocrine tumors of the midgut are relatively rare, these findings are very good news for patients.

We believe our study will change the way that this disease is treated, providing the first drug option for patients who cannot be cured by surgery," said Rudolf Arnold, MD, a professor of internal medicine at Philipps University in Marburg, Germany, and the lead author of the study. "Looking ahead, we are also evaluating the ability of octreotide LAR to slow cancer progression in pancreatic and other neuroendocrine tumors. We are also investigating the molecular make-up of these tumors to determine why some patients do not respond to the drug."

NETs of the digestive tract can occur in the stomach, pancreas, and large intestine as well as the midgut; they can be either malignant or benign. For patients with malignant midgut tumors that are still localized, the median survival is more than 10 years; for patients whose tumors have metastasized, most often to the liver, median survival is about five years.

The standard treatment for these tumors is surgery; other therapeutic options include hepatic embolization, in case of liver metastases, or radioligand therapy, though both approaches carry significant side effects. Previous research has shown that chemotherapy and radiation are not effective.

The current study was a placebo-controlled, double-blind, randomized trial that enrolled 85 patients with newly-diagnosed disease. About 70 percent of the patients had surgery before enrollment in the trial to remove the primary tumor; the remainder had more advanced, inoperable disease. In total, 86 percent of participants had liver metastases. After six months of treatment, 64 percent of patients who received the drug experienced stable disease, versus 37.2 percent of patients who received the placebo. The median time to tumor progression in the octreotide LAR group was 14.3 months, compared with 6 months in the placebo group. Researchers also found that patients with localized disease responded to the drug better than patients with many metastases; about 30 percent of patients in the trial did not respond to the drug.

Because the majority of the patients are still alive, it is too early to determine an overall survival benefit.

The side effects seen in the study were not severe and have been well-established. They include diarrhea, fatigue, fever, and bile stones. Five patients discontinued this trial because of side effects.