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SOURCE: Medscape Medical News

FDG-PET May Have Prognostic Value in Malignant Pleural Mesothelioma

Emma Hitt, PhD

June 4, 2003 (Chicago) - A fluorodeoxyglucose-positron emission tomography (FDG-PET) standardized uptake value (SUV) of more than four may help predict survival in patients with malignant pleural mesothelioma, and the value may predict survival better than histology type in these patients, new research suggests.

"Currently, histology and tumor stage are widely accepted as the best predictors of survival," said Raja M. Flores, MD, from Memorial Sloan-Kettering Cancer Center in New York City.

"CT [computed tomography] and MRI [magnetic resonance imaging] are inaccurate in predicting preoperative stage, and approximately 20% to 25% of patients undergoing attempted surgical resection are found to have undetected disease at the time of surgery," Dr. Flores noted here during his presentation at the 39th annual meeting of the American Society of Clinical Oncology on Monday.

Dr. Flores and colleagues previously found that FDG-PET was useful in identifying patients with occult metastatic disease undetected by CT scan; therefore, they hypothesized that SUV values derived from FDG-PET might predict survival.

The researchers used FDG-PET to evaluate 65 patients with pathologically proven mesothelioma. Patients fasted and received a minimum of 10 mCi of fluorodeoxyglucose. Of the patients, 46 had epithelioid, 17 had mixed, and two had sarcomatoid histology. The corresponding median SUV values were 6.5, 6.8, and 3.8, respectively.

Based on an exploratory statistical analysis, a cut-off SUV of four was chosen to classify patients as low vs. high SUV. For the high-SUV group, median survival was 14 months (n = 52) compared with 24 months for the low-SUV group (n = 13) (P < .04).

High SUV and nonepithelioid histology were associated with the worst prognosis, the researchers found. Patients with SUV greater than four were 3.3 times more likely to die than those with SUV of four or less (P = .03); likewise, those with nonepithelioid histology were 3.2 times more likely to die than those with epithelioid histology (P = .03). In contrast, surgery, age, and sex were not predictive of survival.

"PET SUV and histology may help select patients for treatment in clinical trials, although confirmation in larger studies is warranted," Dr. Flores concluded.

"Up until recently our ability to classify mesothelioma patients into prognostic groups has been limited to retrospective analyses," said Harvey L. Pass, MD, from the Karmanos Cancer Institute in Detroit, Michigan, who discussed the presentation during the session. "Dr. Flores' study represents the largest study to date on this subject, and the data is extremely promising," he added.

However, Dr. Pass pointed out that SUV values must be made uniform from institution to institution. Some other considerations will be to evaluate whether resectable patients have lower SUVs than those who are unresectable and whether histology is related to SUV. "If so, one would expect patients with a nonepithelioid cell type to have a consistently higher SUV than an epithelioid cell type," he said.

Dr. Pass also pointed out that several factors, some of which are independent of prognosis, may influence the uptake of FDG into cells, including microvasculature, GLUT-1 and HIF-1 alpha expression, hexokinase activity, and proliferation rate of cells.

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