The study involved 15 men between the ages of 56 and 79 with advanced metastatic prostate cancer confirmed by biopsies or radiological studies. PET scans were performed using 16b-[18F] fluoro-5a-dihydrotestosterone (FDHT), a radiopharmaceutical specially designed for AR imaging. FDHT-PET findings were compared to bone scintigraphy and CT scan results, with abnormal FDHT uptake noted in the lesions of 10 patients.
FDHT-PET revealed numerous lesions in two patients; one patient had multiple osseous lesions (confirmed by bone scintigraphy), indicating the cancer had spread to the bones, while the other had extensive lymph node lesions (confirmed by CT). In the remaining 8 patients, FDHT-PET detected 10 of 16 osseous lesions identified by bone scintigraphy and all 9 lymph node metastases seen on CT scans. FDHT-PET also found 7 additional lymph node lesions in two patients and unsuspected lymph node lesions in one patient.
To assess whether FDHT is androgen receptor mediated, patients who had shown abnormal FDHT uptake were re-examined with FDHT-PET after a day of flutamide (an androgen-receptor antagonist) therapy. The average AR standardized uptake value (SUV) decreased significantly, as did the tumor-to-muscle ratio of identified lesions.
Dehdashti and her colleagues are encouraged by the evidence that FDHT-PET shows utility in evaluating prostate cancer patients. And, as Dehdashti stated, “We believe FDHT-PET may hold promise in assessing androgen receptor status of prostate cancer and may help to predict response to hormone therapy in prostate cancer patients. Future studies should be conducted in order to assess this capability.”