Better Imaging for Better Prostate Treatment Outcomes
COMBINING PET AND CT SCANS HAS BEEN A POWERFUL DIAGNOSTIC TOOL FOR MANY CANCERS.
But it has not traditionally been as useful for prostate cancer. That changed, thanks to the addition of a novel radioactive tracer molecule called fluciclovine, invented and developed by Mark M. Goodman, PhD, and a team of researchers at Winship Cancer Institute.
Combination PET/CT scans incorporate both positron emission tomography to detect metabolic differences between cancer and noncancerous cells and computed tomography to detect anatomical differences that can reveal the presence, size and shape of cancer. First used successfully to image brain tumors, fluciclovine in 2016 became the first FDA-approved fluorinated ET radiotracer for prostate cancer staging.
David M. Schuster
Ashesh B. Jani
Winship radiation oncologist Ashesh B. Jani, MD, MSEE, FASTRO, the James C. Kennedy Professor in Prostate Cancer, and David M. Schuster, MD, FACR, director of the Division of Nuclear Medicine and Molecular Imaging, wanted to know whether combining this enhanced imaging with conventional imaging could achieve more positive outcomes for men whose disease recurred after their prostate was surgically removed (prostatectomy).
"We knew that conventional imaging was not doing a very good job of detecting recurrent prostate cancer," says Schuster, "so it made sense that radiotherapy treatments based on that imaging would be handicapped. We wanted to change that." He explains that since fluciclovine PET/CT more accurately identifies where and how much prostate cancer is in the body after surgery, they (correctly) theorized that patient outcomes would improve by basing newer, more powerful radiotherapy treatments on this newer, more powerful imaging.
Comparing treatment outcomes
In 2012, Jani and Schuster designed and headed the $2.2 million EMPIRE-1 (Emory Molecular Prostate Imaging for Radiotherapy Enhancement) clinical trial. It enrolled 165 men whose PSA levels dropped close to zero following surgery but then rose again, indicating that cancerous prostate cells were hiding out somewhere in the body.
One group received radiation therapy based on conventional imaging, using bone and either CT or MRI scans. The other group also received radiation therapy based on PET/CT imaging with fluciclovine. After four years, 75.5% of patients in the fluciclovine arm of the study had no evidence of cancer. Only 51.2% of patients whose treatment was guided by conventional imaging were cancer free. What happened? Jani and Schuster say the fluciclovine radiotracer helped clinicians make better decisions about which patient should receive what treatment, and more precisely guided radiation treatment planning.
Fluciclovine helps detect "hot spots"
PET/CT imaging with fluciclovine detected "hot spots" in the pelvis that conventional imaging missed. If PET imaging found no, or more limited, uptake in the pelvic lymph nodes than expected, the radiation field could be reduced. If cancerous cells were found outside the pelvis—meaning the disease was already system-wide—treatment could skip radiation therapy, going straight to systemic hormone or chemotherapy and sparing patients unnecessary radiation.
Advanced fluciclovine imaging is now available at most leading medical institutions. At Emory, clinicians go a step further, registering the PET/CT scan with the radiation planning scan so changes can be made in the size of the target volume. "This extra step," says Jani, "allows us to target the region(s) of prostate cancer more accurately with less possibility of missed areas of cancer."
