|
|
|
|
|
|
|
|
|
|
|||||||
 |
 |
 |
|||||||||
|
Neuroendocrine TumorsBy Joe Munch
“There is an old saying in medicine,” says James Yao, M.D., an associate professor in M. D. Anderson’s Department of Gastrointestinal Medical Oncology: “‘When you hear hoofbeats, think horse, not zebra.’” But in the realm of cancer care, Dr. Yao has his ears perked for zebras—and there may be more of them than once thought. Dr. Yao specializes in treating neuroendocrine tumors (NETs), a group of tumors that includes carcinoid tumors, islet cell tumors, medullary thyroid carcinomas, and pheochromocytomas, all of which arise from hormone-releasing cells in the body. Although most NETs are slow-growing and more indolent than tumors arising from the epithelium, some NETs can be highly malignant and resistant to therapy. NETs were once believed to be extremely uncommon. However, said Dr. Yao, “There are data suggesting that these tumors are not nearly as rare as people think.” For example, in two large autopsy series of more than 15,000 people each, carcinoid tumors were found in about 1% of the people. Another autopsy series examined the occurrence of islet cell tumors, which form in the pancreas. “Islet cell tumors were once thought to be exceedingly rare, with an incidence in the range of 2–3 cases per million per year in the United States,” Dr. Yao said, “but if you look at the autopsy series, you’ll find an incidence of about 1 in 1,000 cases.” To examine the prognostic factors for and the epidemiology of NETs, Dr. Yao and his colleagues identified NETs from the Surveillance, Epidemiology, and End Results Program registries and used associated population data for incidence and prevalence analysis. What they found was surprising: the annual age-adjusted incidence of NETs increased significantly over time, from about 1 in 100,000 in 1973 to more than 5 in 100,000 in 2004. Furthermore, the researchers found that, owing to the tendency of patients to live a long time with slow-growing NETs even after the disease has metastasized, the prevalence of NETs was steadily increasing as well. Dr. Yao said, “If you look at prevalence within the realm of gastrointestinal neoplasms, neuroendocrine tumors are second only to colon cancer. They are actually more common than stomach cancer, pancreatic cancer, esophageal cancer, and hepatobiliary tumors.” In 2000, 197 new patients with NETs were treated at M. D. Anderson; by 2007, that number had more than doubled, to more than 450. According to Dr. Yao, more patients with NETs are coming to M. D. Anderson because of the availability of clinical trials. Currently, the main goal of therapy for NETs is to control hormonal symptoms and tumor growth. NETs should be surgically resected if possible, but there are no data supporting adjuvant therapy, and there is no established standard of post-resection follow-up. “For many decades now, the management of these diseases has been based on small case series and anecdotal data,” Dr. Yao said. “Our main interest is to generate data in terms of how to manage these patients, and that would involve some almost unprecedented efforts in this area, such as doing clinical trials that involve hundreds to thousands of patients.” Such trials have already started. Nearly 300 patients are being enrolled in a phase III trial of bevacizumab (Avastin) for NETs, and nearly 1,000 patients are being enrolled in several ongoing clinical studies of RAD001 (everolimus), a mammalian target of rapamycin inhibitor. “We’re really deeply involved with generating reliable data for the management of these patients,” Dr. Yao said. “That’s one of the reasons we’ve put in a significant effort in terms of raising awareness of the disease by doing these epidemiological studies and really showing that the disease is not nearly as rare as people thought.”
For more information, contact Dr. Yao at 713-792-2828. Other articles in OncoLog, March 2009 issue: Home/Current Issue | Previous Issues | Articles by Topic | Patient Education ©2009 The University of Texas M. D. Anderson Cancer Center |
||||||||
TOP