Is there a diagnostic benefit of late-phase abdomino-pelvic PET/CT after urination as part of whole-body 68 Ga-PSMA-11 PET/CT for restaging patients with biochemical recurrence of prostate cancer after radical prostatectomy?

Abstract

Background To assess the diagnostic value of an additional late-phase PET/CT scan after urination as part of 68 Ga-PSMA-11 PET/CT for the restaging of patients with biochemically recurrent prostate cancer (BCR). Methods This retrospective trial included patients with BCR following radical prostatectomy, who underwent standard whole-body early-phase PET/CT performed 105 ± 45 min and an additional late-phase PET/CT performed 159 ± 13 min after injection of 68 Ga-PSMA-11. Late-phase PET/CT covered a body volume from below the liver to the upper thighs and was conducted after patients had used the bathroom to empty their urinary bladder. Early- and late-phase images were evaluated regarding lesion count, type, localisation, and SUVmax. Reference standard was histopathology and/or follow-up imaging. Results Whole-body early-phase PET/CT detected 93 prostate cancer lesions in 33 patients. Late-phase PET/CT detected two additional lesions in two patients, both local recurrences. In total, there were 57 nodal, 28 bone, and 3 lung metastases, and 7 local recurrences. Between early- and late-phase PET/CT, lymph node metastases showed a significant increase of SUVmax from 14.5 ± 11.6 to 21.5 ± 17.6 (p = 0.00007), translating to a factor of + 1.6. Benign lymph nodes in the respective regions showed a significantly lower increase of SUVmax of 1.4 ± 0.5 to 1.7 ± 0.5 (p = 0.0014, factor of + 1.2). Local recurrences and bone metastases had a SUVmax on late-phase PET/CT that was + 1.7 and + 1.1 times higher than the SUVmax on early-phase PET/CT, respectively. Conclusion In patients with BCR following radical prostatectomy, an additional abdomino-pelvic late-phase 68 Ga-PSMA-11 PET/CT scan performed after emptying the urinary bladder may help to detect local recurrences missed on standard whole-body 68 Ga-PSMA-11 PET/CT. Lymph node metastases show a higher SUVmax and a stronger increase of SUVmax than benign lymph nodes on late-phase PET/CT, hence, biphasic 68 Ga-PSMA-11 PET/CT might help to distinguish between malignant and benign nodes. Bone metastases, and especially local recurrences, also demonstrate a metabolic increase over time.

Preclinical evaluation and first in human study of Al18F radiolabeled ODAP-urea-based PSMA targeting ligand for PET imaging of prostate cancer

“…Interestingly, one patient with Gleason score of 4 + 4 showed more than 10 soft tissue metastases. Similar uptake of PSMA targeted tracer in lung metastases have been reported (35,36). Although [ 18 F]AlF-PSMA-137 PET/CT imaging did not change the stage of these prostate cancer patients, it showed low blood uptake and higher tumor-to-organ ratios at delayed time (Figure 7), which could improve the imaging contrast.…”

“…This was thought to facilitate the detection of intraprostatic lesions, recurrent pelvic lesions, metastatic lymph node lesions and prostate bed lesions. In contrast, 68 Ga-PSMA-11 is rapidly excreted through the urethra (34), leading to significant accumulation in the bladder, and may somewhat obscure the detection of local recurrences (35).…”

Evaluation of [68 Ga]Ga-PSMA-I&T PET/CT with additional late scans of the pelvis in prostate-specific antigen recurrence using the PROMISE criteria

“…Comparable to other publications [ 17 , 21 , 23 , 24 ], the lesion-to-background ratio increased for local recurrences, lymph node, and bone metastases. Also, the gain in the case detection rate on late imaging of 5.7% falls into the range of 0–10% reported in other publications [ 18 , 19 , 21 , 22 , 24 ]. However, the relationship between imaging of a patient at two time points is often more complex than the comparison of positive vs. negative cases.…”

“…For example, early scans in the first 10 min after radioligand injection may help to visualize pelvic lesions with pathological PSMA expression before urinary activity interferes with image interpretation [ 15 , 16 ]. On the other hand, several studies have described an increasing PSMA ligand uptake from standard to late imaging in most PCa-related lesions [ 17 – 22 ]. This was often paralleled by a decreasing tracer uptake of the background tissue [ 17 , 21 , 23 ].…”

The Value of Multimodality PET/CT Imaging in Detecting Prostate Cancer Biochemical Recurrence

“…Morawitz et al. ( 72 ) found that 68 Ga-PSMA-11 PET/CT scanning in the late abdominal and pelvic stage after emptying the bladder was helpful to detect missed local recurrence lesions. Uprimny et al.…”