Imaging amino acid transporters with PET/CT significantly alters intended management plans for patients with brain tumors, according to research in the March issue of The Journal of Nuclear Medicine. As a result of imaging with the radiopharmaceutical 3,4-dihydroxy-6-F-18-fluoro-L-phenylalanine (F-18-DOPA), referring physicians changed the intended management plan for 41 percent of patients with brain tumors.
Contrast-enhanced MRI is most frequently used to diagnose and monitor patients with brain tumors. After initial treatment, however, the assessment of recurrence by MRI can be difficult as contrast enhancement cannot reliably distinguish tumor recurrence from radiation necrosis. On the other hand, PET/CT imaging provides a highly accurate image that is beneficial for detecting primary and recurrent high- and low-grade brain tumors.
Franziska Walter, MD, of the department of molecular and medical pharmacology at University of California, Los Angeles (UCLA), and colleagues designed a prospective survey to determine how referring physicians used data from F-18-DOPA PET/CT imaging to inform or change patient management.
The researchers gave five referring physicians a survey prior to performing PET/CT scans with F-18-DOPA on patients with known or suspected brain tumors. Of the 58 patients, seven had a suspected primary brain tumor and 51 had a suspected recurrent brain tumor.
The prescan surveys asked about indication, tumor histology or grade, level of suspicion for tumor recurrence and planned management. Soon after the PET/CT scans, the referring physicians were asked to complete a survey to categorize PET findings, level of suspicion for primary or recurrent brain tumors and intended management changes. Six months following the scans, the physicians took another survey dealing with recurrence and survival. All referring physicians completed the surveys, yielding a 100 percent response rate.
Of the cases included in the survey, after adding the PET/CT findings to other diagnostic data, the clinical suspicion for recurrence increased in 33 percent, remained unchanged in 50 percent and decreased in 17 percent of patients. As a result, several changes in management were recommended, with changes from “watch and wait” to chemotherapy (25 percent) and from chemotherapy to “watch and wait” (17 percent) occurring most frequently. Seventy-five percent of the recommended changes were implemented.
“We know that F-18-DOPA PET/CT imaging is highly accurate for detecting brain tumors, and in our research we’ve shown that this imaging modality has a significant impact on patient management,” said Johannes Czernin, MD, department of molecular and medical pharmacology at UCLA, in a statement. “In the future, we will initiate multicenter trials to determine whether these management changes have an impact on patient outcome. We believe that amino-acid transport imaging with PET will eventually be an important and frequently used imaging modality in brain cancer.”
The researchers noted the study was not designed to examine the accuracy of F-18-DOPA for detecting primary or recurrent brain tumors. However, they observed that the seven biopsies performed on the basis of PET/CT findings confirmed PET/CT results. In addition, patients with F-18-DOPA-positive tumors had significantly shorter survivals than those with F-18-DOPA-negative tumors, according to Walter and colleagues.