OGTT testing may help counsel patients before total pancreatectomy with islet autotransplantation

Last Updated: 2016-12-06

By Will Boggs MD

NEW YORK (Reuters Health) - Lower oral glucose tolerance test (OGTT) glucose values and higher beta-cell function predict insulin independence after total pancreatectomy with islet autotransplantation (TPIAT) for chronic pancreatitis, researchers report.

"Our study suggests that preoperative glucose status as assessed by OGTT is related to the requirement for insulin therapy 1 year after TPIAT and should be considered in the diagnostic work-up prior to surgery," Dr. Rita R. Kalyani from Johns Hopkins University in Baltimore, Maryland, told Reuters Health by email.

Up to 50% of patients who undergo TPIAT for refractory abdominal pain secondary to chronic pancreatitis achieve insulin independence, Dr. Kalyani and colleagues note in The Journal of Clinical Endocrinology & Metabolism, online November 21. But the average one-year insulin independence rate appears to be closer to 28%, they add.

The team sought to identify preoperative glycemic predictors of insulin independence (as defined by no requirement for insulin therapy and a hemoglobin A1c <6.5%) one year after TPIAT among 34 patients without baseline diabetes.

At one year, 10 patients (29%) were completely insulin independent, the researchers found.

All patients who had preoperative impaired fasting glucose or impaired glucose tolerance were insulin-dependent at one year, as were all five patients with preoperative HbA1c >5.7% (39 mmol/mol).

In regression analyses, normal preoperative glycemic status (compared with prediabetes) was a significant predictor of one-year insulin independence.

OGTT predictors of insulin independence included lower fasting glucose and lower one-hour and two-hour glucose values.

Beta-cell function (HOMA-beta of at least 140.8%) was the best predictor of insulin independence, whereas one-hour glucose on OGTT (>=119 mg/dL) was the best predictor of insulin dependence.

"Preoperative glycemic predictors offer the promise to identify those most likely to have insulin independence long-term," the researchers conclude. "Though further studies are needed, our results support the potential utility of OGTT in pre-surgical evaluation as a low-cost and potentially very useful preoperative diagnostic assessment to improve selection and counseling of TPIAT candidates regarding postoperative insulin independence."

"If patients have an impaired glucose state preoperatively, our results suggest that they should be counseled on the potentially higher likelihood of postoperative diabetes and need for insulin therapy long-term when considering whether to pursue TPIAT," Dr. Kalyani concluded.

Dr. Melena Bellin, director of research at the University of Minnesota's islet autotransplant program in Minneapolis, told Reuters Health by email, "While we often focus on insulin or C-peptide levels to measure beta-cell function, in this case fasting and OGTT stimulated glucose levels were more significant than insulin or C-peptide levels at distinguishing patients who were insulin independent vs. dependent after surgery, although a lower HOMA-beta - a measure which incorporates both insulin and glucose measurements - also predicted insulin dependence."

"Providers should realize that a simple fasting glucose and oral glucose tolerance test with 1 and 2 hour glucoses can provide important prognostic information for likelihood of achieving insulin independence after TPIAT," said Dr. Bellin, who was not involved in the new work. "Such measures can be easily incorporated to assessing and counseling patients on their specific diabetes risk when TPIAT is considered."

"While risk of diabetes is most often a secondary consideration (to pain control/quality of life) in selecting patients for TPIAT, it is very important that patients are provided a realistic expectation of outcomes in preoperative counseling," she concluded. "Some patients may choose not to undergo TPIAT knowing that their testing before surgery puts them at very high risk for lifelong insulin dependence after surgery."

Dr. Yvette C. Tanhehco from Columbia University Medical Center in New York, who recently reviewed the use of pancreatic islet autotransplantation for malignant and nonmalignant indications, said that "whether someone is predicted to be insulin independent or dependent after TPIAT should not be the deciding factor in proceeding with the procedure."

"While these findings are interesting and the study was well done, the total sample size was small and the study was only done at one institution," she told Reuters Health by email. "I think further studies involving multiple institutions and a larger sample size should be performed to see if their findings will hold true."

SOURCE: http://bit.ly/2h0NTRj

J Clin Endocrinol Metab 2016.