Newswise — Researchers at University of California, San Diego School of Medicine have determined that certain gastrointestinal stromal tumors (GISTs) are more deadly than previously reported in medical literature. Findings are published online in the Journal of Gastrointestinal Surgery.

“While GISTs are rare, we have found that certain groups of these tumors result in a much higher mortality than expected,” said Jason Sicklick, MD, assistant professor of surgery at UC San Diego School of Medicine and a surgical oncologist at UC San Diego Health. “The 5-year mortality rate for malignant GISTs of less than 2 centimeters is 12.1 percent. This finding may be helpful in creating new guidelines for the treatment of these tumors.”

GISTs are most commonly found in the stomach and small intestine and have significant variability in terms of size and malignant behavior. Sicklick noted that up to 30 percent of patients have GISTs less than 2 centimeters in size, or slightly more than one-half inch. More than 79 percent of patients have localized disease, while 11.4 percent have regional or distant metastatic disease. Previously, researchers did not expect any disease to have spread.

“For this study, we identified 378 patients with malignant GISTs of less than 2 cm between 2001 and 2011 from the SEER database,” said Taylor M. Coe, first author and fourth-year medical student at UC San Diego School of Medicine. “While the distribution of disease was almost equal between men and women, African-Americans are 2.1 times more likely than Caucasians to develop GISTs. The reasons are unknown and need to be further evaluated.”

Sicklick added that further studies are needed to develop novel risk assessments for patients with these small tumors and to determine appropriate indications for surgery and/or medical therapy.

Previous research by Sicklick and researchers at UC San Diego Moores Cancer Center newly defined the epidemiology of GISTs, including at-risk populations in the United Stated, incidence rates, survival trends, risk factors for GISTs and associations with the occurrence of other cancers.

This study was funded in part by the National Institutes of Health (TL1 TR001443, KL2 RR031978, K08 CA168999).

Co-authors include Katherine E. Fero, Paul Fanta, Robert Mallory, Chih-Min Tang, and James Murphy, all of UC San Diego.