Initial experience of Ga-68 prostate-specific membrane antigen positron emission tomography/computed tomography imaging in evaluation of biochemical recurrence in prostate cancer patients

Abstract

Gallium-68 labeled prostate-specific membrane antigen (Ga-68 PSMA) ligand (HBED-CC) is a novel tracer used for prostate cancer imaging. The aim of the study was to investigate the performance of Ga-68 PSMA positron emission tomography/computed tomography (PET/CT) in patients with biochemical recurrence (BCR) after definitive treatment. Scans of 96 consecutive patients were analyzed. Sixty-two patients received external beam radiotherapy, 34 underwent radical prostatectomy (RP), and 20 patients were on androgen deprivation therapy. Patients with prostate-specific antigen (PSA) level ≥>0.2 ng/mL following RP and PSA rise by 2 ng/mL or more above the nadir PSA following RT (Phoenix criteria) was considered as BCR, respectively. All patients underwent contrast-enhanced PET/CT after injection of 67–111 MBq Ga-68 PSMA ligand. Detection rates were correlated with serum PSA level. Detection rate for nodal metastases was compared with CT. Results of the scan were validated by using either biopsy or follow-up imaging or clinical follow-up. Seventy-four (77%) patients showed abnormal finding in Ga-68 PSMA PET/CT. The median serum PSA level of the population was 5.5 ng/ml (range 0.2–123 ng/ml). The median PSA of the positive scans was higher than that of the negative scans (6 vs. 1.7 ng/ml) and was statistically significant ( P = 0.001 by Mann–Whitney U-test). In post-RP group, the detection rates were 23%, 50%, and 82% for PSA <1, 1–2, and >2 ng/ml, respectively. For post-RT, the detection was 86%, 85%, and 95% for PSA 2–5, 5.1–10, and >10 ng/ml, respectively. PSMA PET/CT revealed nodal metastases in 52 (54%) patients while CT showed pathological nodes only in 27 (28%) patients. Overall PSMA PET/CT revealed more number of nodes than CT (111 vs. 48 nodal station). PSMA PET/CT showed relapse in prostate/prostatic bed in 26 (27%) patients, nodal metastases in 50 (52%), skeletal metastases in 20 (21%), and other sites in 4 (4%) patients. Ga-68 PSMA PET/CT has high detection rate for localizing the site of recurrence in patients with biochemical failure and is superior to CT scan in the detection of nodal disease.

Pan-Asian adapted ESMO Clinical Practice Guidelines for the diagnosis, treatment and follow-up of patients with prostate cancer

“… For patients with a local recurrence following RP and no distant metastases, the pros and cons of local salvage therapy should be discussed, taking into account life expectancy and the long natural history of isolated local recurrences [III, C]. Patients with biochemical relapse after radical RT who may be candidates for local salvage or metastasis-directed treatment should undergo imaging with next generation imaging tools such as 68 Ga-PSMA -PET–CT 50 , 95 or whole-body MRI [III, B]. Early ADT is not routinely recommended for men with biochemical relapse unless they have a rapid PSA doubling time, symptomatic local disease or proven metastases [II, D].…”

“…Patients with biochemical relapse after radical RT who may be candidates for local salvage or metastasis-directed treatment should undergo imaging with next generation imaging tools such as 68 Ga-PSMA -PET–CT 50 , 95 or whole-body MRI [III, B].…”

Variability of radiotherapy volume delineation: PSMA PET/MRI and MRI based clinical target volume and lymph node target volume for high-risk prostate cancer

“…A medical report of the course of illness and written reports from the radiologist and nuclear medicine physician were also provided, and the imaging could be viewed simultaneously in the Radiology Information System (RIS) and Hospital Information System (HIS) system. Regarding the determination of lymph nodes, increased local uptake of pelvic and retroperitoneal lymph nodes was thought to be metastasis, while in MRI, a threshold of 1.0 cm short-axis node diameter for oval nodes and 0.8 cm for round nodes was used as a criterion for lymph node metastasis [ 19 ]. GTV includes definite primary prostate foci based on the abovementioned imaging basis; if accompanied by pelvic lymph node metastases, GTVn is outlined.…”