Patients receiving radiation therapy for recurrent prostate cancer after prostatectomy may have better outcomes if imaging with the positron emission tomography (PET) radiotracer fluciclovine is used to guide their treatment.

Results from an ongoing study show that assessing tumors with fluciclovine PET/CT scans leads to significant differences in the areas to receive radiotherapy, compared to conventional computed tomography (CT) or magnetic resonance imaging (MRI) techniques, with similar toxicities.

The study, “Impact of ¹⁸F-Fluciclovine PET on Target Volume Definition for Postprostatectomy Salvage Radiotherapy: Initial Findings from a Randomized Trial,” was published in The Journal of Nuclear Medicine.

“This is the first study of its kind demonstrating changes in post-surgery radiotherapy target design with advanced molecular imaging in recurrent prostate cancer, with no demonstrated increase in early radiotherapy side effects,” Ashesh B. Jani, MD, of the Winship Cancer Institute of Emory University in Atlanta, Georgia, said in a news release.

Radical prostatectomy and radiotherapy are the two main curative options for localized prostate cancer. Radiation therapy, in particular, can either be administered right after the surgery, or when a patient’s cancer returns following surgery.

While CT and MRI are commonly used to detect the areas of high risk that should receive radiation therapy, they have low sensitivity, and better imaging tools are needed to define the clinical target volume, or areas to receive radiotherapy.

The PET tracer fluciclovine, a synthetic amino acid analog, has shown promise in staging and restaging prostate cancer patients with high accuracy.

Researchers at Emory University designed a Phase 2/3 randomized clinical trial (NCT01666808) to evaluate whether PET/CT scans with fluciclovine could improve the selection and outcomes of patients with a strong suspicion of prostate cancer recurrence after surgery. A total of 162 patients are expected to be recruited.

So far, 96 patients have been enrolled in the trial, all of whom underwent initial treatment planning based on CT or MRI results. Then, patients were randomized to receive radiation therapy based either on that first assessment or on results from a fluciclovine PET/CT scan.

Results from this ongoing trial have shown that assessment with PET/CT scan led to significant differences in the areas to receive radiotherapy. Indeed, patients randomized to the PET/CT assessment had higher doses of radiation delivered to the penile bulb, but no differences in bladder or rectal radiation. Of note, the process did not induce significant differences in toxicity in the genital, urinary, or gastroinstestinal tracts.

But despite the differences in areas receiving radiation, longer follow-up is now required to determine if radiation therapy based on this PET tracer is better at preventing prostate cancer recurrence than standard imaging methods.