Dr Vojnic Highlights FET-PET's Role in Confirming Glioma Progression

The recent FDA approval of floretyrosine F 18 (Pixclara), a fluoroethyl-L-tyrosine (FET) positron emission tomography (PET) imaging agent, gives clinicians a new way to tell true glioma progression from treatment-related changes. Morana Vojnic, MD, MBA, director of neuro-oncology at Rutgers Cancer Institute, described the approval the most important development in the field over the past 12 months. FET-PET is approved for use with other diagnostic evaluations to differentiate recurrent or progressive glioma from treatment-related change in adults and pediatric patients 1 month and older.

After standard surgery followed by radiation and chemotherapy, about 30% to 50% of patients with glioma develop pseudoprogression. Vojnic described pseudoprogression as false progression. Treatment-related changes in the brain can appear on standard MRI and look like the tumor is returning much sooner than expected. In the past, many of these patients had another surgery, only for clinicians to find radiation necrosis or radiation treatment effect rather than tumor.

Vojnic said the field has worked for years on imaging techniques that can make this distinction. Existing options, including MRI perfusion and MR spectroscopy, are not ideal. Their sensitivity for separating tumor from radiation treatment effect ranges from about 60% to 80%.

FET-PET adds another option. Vojnic cited studies reporting a sensitivity of about 91% and a specificity of about 86% for distinguishing active tumor from radiation treatment effect.

She said the improved accuracy helps in several ways. It can spare patients an unnecessary change in treatment, and it gives clinicians more confidence to keep patients on their current therapy. Vojnic explained that treatment effect tends to resolve over time, whereas true tumor grows. Allowing patients to stay on current treatment and delaying new therapy until true progression is confirmed is therefore important. The test can also spare patients an additional surgical procedure.