Early PET imaging with [68]Ga-PSMA-11 increases the detection rate of local recurrence in prostate cancer patients with biochemical recurrence

Prognostic significance of a negative PSMA PET/CT in biochemical recurrence of prostate cancer

BACKGROUND

Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) is becoming standard of care for men with biochemical recurrence (BCR) of prostate cancer. The implications of a negative PSMA PET/CT scan in this population remain unclear. This study aims to assess the outcome of patients with BCR post radical prostatectomy (RP) who have negative [18F]DCFPyL PET/CT scan at relapse.

METHODS

This is a post-hoc subgroup analysis of a prospective non randomized clinical trial. One hundred and one patients (median age, 75 years) with BCR after RP, who tested negative on [18F]DCFPyL PET/CT and subsequently either underwent salvage radiotherapy (sRT) with or without androgen deprivation therapy (ADT) or were followed without active treatment, were included. Freedom from progression (FFP) after negative PSMA PET/CT was determined based on follow-up imaging selected as per clinical practice. Uni- and multivariate Cox regression analyses were performed to examine the association of patients' characteristics, tumor-specific variables, and treatment with clinical progression at the last follow-up. FFP at 1-, 2-, and 3-year were reported using Kaplan Meier analysis.

RESULTS

The median PSA level at PET/CT was 0.56 ng/mL (range, 0.4-11.3). Sixty five (64%) patients were followed without receiving further treatment, and 36 (36%) received sRT (18% to the prostate bed only and 18% to the prostate bed and pelvic lymph nodes) within 3 months of the PSMA PET. Seventeen of the sRT patients (17 of 36, 47%) received concomitant androgen deprivation therapy (ADT). Median follow-up was 39 months. Subsequent clinical progression was detected in 21 patients (21%), with 52% in pelvic lymph nodes, 52% in the prostatic fossa, 19% in distant lymph nodes, 14% in lungs, and 10% in bones. The FFP was 95% (95% CI: 91%-99%) at 12 months, 87% (95% CI: 81%-94%) at 24 months, and 79% (95% CI: 71%-88%) at 36 months. Multivariate Cox regression analysis revealed that an initial International Society of Urological Pathology (ISUP) grade 5 was significantly associated with clinical progression at the last follow-up (hazard ratio, 5.1, P value, 0.04). Furthermore, the receipt of sRT correlated significantly with lower clinical progression at the last follow-up (hazard ratio, 0.2, P value, 0.03), whereas other clinical and tumor-specific parameters did not. Following surveillance-only and sRT, 29% (19 of 65) and 6% (2 of 36) of patients, respectively, showed clinical progression. In the sRT group, no significant difference was observed in FFP between patients who underwent sRT to the prostatic fossa versus those who received sRT to the prostatic fossa and pelvic lymph nodes, although the numbers in these groups were small.

CONCLUSIONS

This study suggests that salvage radiotherapy is associated with a decreased or delayed clinical progression in patients with biochemical recurrence following radical prostatectomy who have negative PSMA PET/CT scan results. The analysis also underscores the prognostic significance of the initial ISUP grade, with ISUP grade 5 being associated with worse outcomes.

TRIAL REGISTRATION

Registered September 14, 2016; NCT02899312 .

Predictive significance of intraprostatic volumetric parameters derived from early and standard time 68Ga-PSMA PET/CT images in newly diagnosed prostate cancer patients

OBJECTIVE

To investigate the relationship between intraprostatic 68Ga-prostate-specific membrane antigen (PSMA) uptake values and volumetric parameters derived from early pelvic and standard-time whole-body 68Ga-PSMA PET/computed tomography (CT) images in untreated prostate cancer (PCa) patients, and to assess the predictive significance of these data in relation to disease prognosis, comparing them with the Gleason score, clinical risk classification and the presence of metastatic disease detected in 68Ga-PSMA PET/CT imaging.

METHODS

Eighty-one newly diagnosed PCa patients underwent early phase pelvic imaging at the 5th minute and standard time whole-body imaging at the 60th minute. Various threshold values were used in intraprostatic delineations to compute maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), intraprostatic PSMA tumor volume and intraprostatic total lesion PSMA uptake. Correlations between early and standard time measurements, as well as changes in SUV parameters over time, were examined. The association of these values with Gleason score, clinical risk status (National Comprehensive Cancer Network), and metastatic disease was explored.

RESULTS

SUVmax measurements from both early and standard time images distinguished all three groups (clinical risk scores, Gleason score and metastatic group), with standard imaging demonstrating statistical superiority in receiver operating characteristic analyses. Strong correlations were observed between early and standard-time PET parameters. Changes in intraprostatic SUVmax and SUVmean values over time did not exhibit predictive value.

CONCLUSION

Although intraprostatic PSMA PET parameters generally aligned at both early and standard times, parameters obtained from standard time images showed more robust correlations with clinical risk scores, Gleason score and metastasis status in newly diagnosed, untreated PCa patients.

Performance evaluation of Gallium-68 radiopharmaceuticals production using liquid target PETtrace 800 cyclotron

Due to increased demand, cyclotron has an expanding role in producing Gallium-68 (68Ga) radiopharmaceuticals using solid and liquid targets. Though the liquid target produces lower end-of-bombardment activity compared to the solid target, our study presents the performance of 68Ga radiopharmaceuticals production using the liquid target by evaluating the end-of-bombardment activity and the end-of-purification activity of [68Ga]GaCl3. We also present the effect of increasing irradiation time, which significantly improves the end-of-synthesis yield. From the result obtained, the end-of-bombardment activity produced was 4.48 GBq, and the [68Ga]GaCl3 end-of-purification activity produced was 2.51 GBq with below-limit metallic impurities. Increasing the irradiation time showed a significant increase in the end-of-synthesis activity from 1.33 GBq to 1.95 GBq for [68Ga]Ga-PSMA-11 and from 1.13 GBq to 1.74 GBq for [68Ga]Ga-DOTA-TATE. Based on the improvements made, the liquid target production of 68Ga radiopharmaceuticals is feasible and reproducible to accommodate up to 5 patients per production. In addition, this work also discusses the issues encountered, together with the possible corrective and preventative measures.

Is there more than meets the eye in PSMA imaging in prostate cancer with PET/MRI? Looking closer at uptake time, correlation with PSA and Gleason score

BACKGROUND

In patients with increasing PSA and suspicion for prostate cancer, but previous negative biopsies, PET/MRI is used to test for tumours and target potential following biopsy. We aimed to determine different PSMA PET timing effects on signal kinetics and test its correlation with the patients' PSA and Gleason scores (GS).

METHODS

A total of 100 patients were examined for 900 s using PET/MRI approximately 1-2 h p.i. depending on the tracer used (⁶⁸Ga-PSMA-11, ¹⁸F-PSMA-1007 or ¹⁸F-rhPSMA7). The scans were reconstructed in static and dynamic mode (6 equal frames capturing "late" PSMA dynamics). TACs were computed for detected lesions as well as linear regression plots against time for static (SUV) and dynamic (SUV, SUL, and percent injected dose per gram) parameters. All computed trends were tested for correlation with PSA and GS.

RESULTS

Static and dynamic scans allowed unchanged lesion detection despite the difference in statistics. For all tracers, the lesions in the pelvic lymph nodes and bones had a mostly negative activity concentration trend (78% and 68%, resp.), while a mostly positive, stronger trend was found for the lesions in the prostate and prostatic fossa following RPE (84% and 83%, resp.). In case of ⁶⁸Ga-PSMA-11, a strong negative (R_min = - 0.62, R_max = - 0.73) correlation was found between the dynamic parameters and the PSA. ¹⁸F-PSMA-1007 dynamic data showed no correlation with PSA, while for ¹⁸F-rhPSMA7 dynamic data, it was consistently low positive (R_min = 0.29, R_max = 0.33). All tracers showed only moderate correlation against GS (R_min = 0.41, R_max = 0.48). The static parameters showed weak correlation with PSA (R_min = 0.24, R_max = 0.36) and no correlation with GS.

CONCLUSION

"Late" dynamic PSMA data provided additional insight into the PSMA kinetics. While a stable moderate correlation was found between the PSMA kinetics in pelvic lesions and GS, a significantly variable correlation with the PSA values was shown depending on the radiotracer used, the highest being consistently for ⁶⁸Ga-PSMA-11. We reason that with such late dynamics, the PSMA kinetics are relatively stable and imaging could even take place at earlier time points as is now in the clinical routine.

(18F)-PSMA-1007PET/CT in patients with biochemical recurrence after radical prostatectomy: Diagnostic performance and impact on treatment management

Objective

To evaluate the diagnostic performance of (18F)-PSMA-1007 PET/CT in prostate cancer patients with biochemical recurrence (BCR) after radical prostatectomy and the effect of (18F)-PSMA-1007 PET/CT on treatment strategy.

Methods

A total of 114 patients with BCR after radical prostatectomy who performed (18F)-PSMA-1007 PET/CT were retrospectively analyzed. The Gleason scores (GS), maximum standardized uptake values (SUVmax) and the diagnostic performance were compared according to different prostate-specific antigen (PSA) groups. To evaluate the impact of (18F)-PSMA-1007 PET/CT on treatment management, we also collected subjects' therapy before and after PET/CT. The PSA value was monitored to evaluate the biochemical response.

Results

(18F)-PSMA-1007PET/CT was positive in 92/114 patients (80.7%). The detection rates were 20/34 (58.8%), 13/17 (76.5%), 15/17 (88.2%) and 44/46 (95.7%) for PSA levels of 0.2-<0.5, 0.5-<1, 1-<2, ≥2 ng/ml. The positive lesions on PET/CT revealed local recurrence in 24/114 (21.1%) patients, lymph nodes metastases in 54/114 (47.4%) and metastatic sites in bone, lung, and others in 75/114 (65.8%). A significant positive correlation was observed between the GS/ SUVmax and PSA level (r1 = 0.375, r2 = 0.336, P<0.001). As a result of the (18F)-PSMA-1007 PET/CT, therapeutic decision-making changed in 60/114 (52.6%) patients. With a follow-up of 11.0 ± 6.4 months, 81/114 PSA were collected after treatment guided by (18F)-PSMA-1007 PET/CT, and in 42/81 (51.9%) of patients, serum PSA levels decreased of more than 60%.

Conclusion

(18F)-PSMA-1007 PET/CT has a high lesion detection rate for recurrent prostate cancer (PCa) and could have significant implications in decision-making treatment plan for the majority of PCa patients.

Evaluation of a radiomics nomogram derived from Fluoride-18 PSMA-1007 PET/CT for risk stratification in newly diagnosed prostate cancer

OBJECTIVE

The aim of this study was to evaluate the performance of Fluoride-18 (18F)-PSMA-1007-PET/CT radiomics for the tumor malignancy and clinical risk stratification in primary prostate cancer (PCa).

MATERIALS AND METHODS

A total of 161 pathological proven PCa patients in a single center were retrospectively analyzed. Prostate-specific antigen (PSA), Gleason Score (GS) and PET/CT indexes (SUVmin, SUVmax, and SUVmean) were compared according to risk stratification. Radiomics features were extracted from PCa 18F-PSMA-1007-PET/CT imaging. The radiomics score integrating all selected parameters and clinicopathologic characteristics was used to construct a binary logistic regression and nomogram classifier. Predictors contained in the individualized prediction nomogram included radiomics score, PSA level and metastasis status.

RESULTS

The radiomics signature, which consisted of 30 selected features, was significantly associated with PSA level and Gleason score (P < 0.001 for both primary and validation cohorts). Predictors contained in the individualized prediction nomogram included radiomics score, PSA level and metastasis status. The model showed good discrimination with an area under the ROC curve of 0.719 for the GS. Combined clinical-radiomic score nomogram had a similar benefit to utilizing the PET/CT radiomic features alone for GS discrimination.

CONCLUSION

The 18F-PSMA-1007-PET/CT radiomics signature can be used to facilitate preoperative individualized prediction of GS; incorporating the radiomics signature, PSA level, and metastasis status had similar benefits to those of utilizing the PET/CT radiomics features alone.

Hybrid imaging with [68Ga]PSMA-11 PET-CT and PET-MRI in biochemically recurrent prostate cancer

AIM

To compare [⁶⁸Ga]PSMA-11 PET-CT, [⁶⁸Ga]PSMA-11 PET-MRI and MRI in a cohort of prostate cancer (PCa) patients in biochemical recurrence after initial curative therapy.

MATERIALS AND METHODS

Fifty-three patients with biochemically recurrent PCa underwent whole-body [⁶⁸Ga]PSMA-11 PET-CT 1 hour post-injection (p.i.) followed by [⁶⁸Ga]PSMA-11 PET-MRI 2.5 hours p.i., including a multiparametric MRI pelvic protocol examination. Imaging data analysis consisted of visual (qualitative) evaluation of the PET-CT, PET-MRI and MRI scans, as well as semi-quantitative and quantitative analyses of the PET and MRI data, including calculation of the parameters standardized uptake value (SUV) and apparent diffusion coefficient (ADC) derived from the PCa lesions. Association analysis was performed between imaging and clinical data, including PSA level and Gleason score. The results were considered significant for p-values less than 0.05 (p < 0.05).

RESULTS

The hybrid imaging modalities [⁶⁸Ga]PSMA-11 PET-CT and PET-MRI were positive in more patients than MRI alone. In particular, PET-CT detected lesions suggestive of PCa relapse in 34/53 (64.2%), PET-MRI in 36/53 (67.9%) and MRI in 23/53 patients (43.4%). While no significant differences in lesion detection rate were observed between PET-CT and PET-MRI, the latter was particularly efficient in detection of local recurrences in the prostate bed mainly due to the contribution of the MRI part of the modality. Association analysis revealed a statistically significant increase in the probability of a positive scan with increasing PSA levels for all imaging modalities. Accordingly, there was no significant association between scan positivity rate and Gleason score for any imaging modality. No significant correlation was observed between SUV and ADC values in lymph node metastases.

CONCLUSION

[⁶⁸Ga]PSMA-11 PET-CT and PET-MRI provide equally good detection rates for PCa recurrence, both outperforming stand-alone MRI.

The 18F-PSMA-1007 PET/CT performance on metastasis status and therapy assessment in oligo-metastasis prostate cancer

Objective

The prostate-specific membrane antigen (PSMA) PET/CT is potentially identifying patients with oligo-metastasis who would be deemed to only have localized disease in the traditional approaches. However, the best selected oligo-metastasis prostate cancer (PCa) patients most likely to benefit from system androgen deprivation therapy (ADT) are still unknown. The aim of this study was to explore the potential 18F-PSMA-1007 PET/CT parameters and clinicopathologic characteristics for oligo-metastasis PCa discrimination and follow-up evaluation.

Materials and methods

A total of 180 retrospective patients with different metastasis burdens (PCa of none-metastases, oligo-metastases, and poly-metastases), different metastasis status (untreated and recurrent oligo-metastases), and follow-up ADT were included respectively. A one-way analysis of variance was used to evaluate whether PET/CT parameters and clinicopathologic characteristics were different and univariate/multivariate logistic regression models were applied to assess independent predictors in the metastasis burdens group (89/180). Selected predictors were further compared between different metastasis statuses to test the diagnostic accuracy (69/180). The predictor efficiency was evaluated by the ROC and the cut-off value was used to test the ADT response-to-treatment with a longitudinal cohort (22/180) from untreated baseline to 3-15 months.

Results

The significant group differences were observed on SUVmax (P = 0.012), International Society of Urologic Pathologists (ISUP, P&lt;0.001) and Gleason Score (P&lt;0.001). Poly-Metastases patients had higher SUVmax, ISUP and Gleason Score compared to Non-Metastases and Oligo-Metastases patients, respectively (P&lt;0.05, all), and no difference between Non-Metastases and Oligo-Metastases. The SUVmax, ISUP and Gleason Score were independent predictors for metastasis burdens discrimination. The untreated and recurrent oligo-metastases lesions SUVmax were also different (P = 0.036). The AUC of ROC for oligo-metastasis prediction was 0.658 (P = 0.039) when the primary prostatic carcinoma focus SUVmax was higher than 28.22, ADT response-to-treatment patients (5/5 in 22) were all progress in a follow-up test.

Conclusion

The SUVmax can discriminate PCa metastasis degree and oligo-metastasis status. The ADT-treated oligo-metastasis patient may still have disease progression when the primary prostatic carcinoma focus SUVmax is greater than 28.22.

18F-PSMA-1007 PET/CT Performance on Risk Stratification Discrimination and Distant Metastases Prediction in Newly Diagnosed Prostate Cancer

Objective

To evaluate the prediction performance of ¹⁸F-PSMA-1007 PET/CT and clinicopathologic characteristics on prostate cancer (PCa) risk stratification and distant metastatic prediction.

Materials and Methods

A retrospective analysis was performed on 101 consecutively patients with biopsy or radical prostatectomy proved PCa who underwent ¹⁸F-PSMA-1007 PET/CT. The semi-quantitative analysis provided minimum, maximum and mean standardized uptake (SUVmin, SUVmax and SUVmean) of PCa. Association between clinicopathologic characteristics (total prostate-specific antigen, tPSA and Gleason Score, GS) and PET/CT indexes were analyzed. The diagnostic performance of distant metastatic on PET/CT parameters, tPSA and GS was evaluated using logistic regression analyses. A path analysis was conducted to evaluate the mediating effect of tPSA level on the relation between semi-quantitative parameters of primary tumors and metastatic lesions.

Results

The PET/CT parameters were all higher in high risk stratification subgroups (tPSA>20 ng/mL, GS ≥ 8, and tPSA>20 ng/mL and/or GS ≥ 8, respectively) with high sensitivity (86.89%, 90.16% and 83.61%, respectively). The SUVmax, tPSA and GS could effectively predict distant metastatic with high sensitivity of SUVmax (90.50%) compared with tPSA (57.14%) and GS (55.61%). With a cutoff value of 29.01ng/mL for tPSA, the detection rate of distant metastasis between low and high prediction tPSA group had statistical differences (50.00% vs. 76.60%, respectively; P = 0.006) which was not found on guideline tPSA level (P>0.05). 6/15 (40%) patients tPSA between 20ng/mL to 29.01ng/mL without distant metastases may change the risk stratification. Finally, tPSA had a partial mediating effect on SUVmax of primary tumors and metastases lesions.

Conclusion

The ¹⁸F-PSMA-1007 PET/CT SUVmax has a higher sensitivity and can be an “imaging biomarker” for primary PCa risk stratification. The prediction tPSA level (29.01 ng/mL) is more conducive to the assessment of distant metastasis and avoid unnecessary biopsy.

Early Injection of Furosemide Increases Detection Rate of Local Recurrence in Prostate Cancer Patients with Biochemical Recurrence Referred for 68Ga-PSMA-11 PET/CT

The aim of this study was twofold. First, we aimed to assess the impact of forced diuresis with early furosemide injection on the detection rate of local recurrence in prostate cancer patients with biochemical recurrence referred for 68Ga-labeled Glu-NH-CO-NH-Lys(Ahx)-HBED-CC (68Ga-PSMA-11) PET/CT. Second, we determined whether intravenous administration of furosemide shortly after tracer injection increases renal washout of 68Ga-PSMA-11 before it binds to the PSMA receptor with possible influence on biodistribution and intensity of tracer uptake in organs with physiologic tracer accumulation. Methods: In a retrospective analysis, 2 different groups with 220 prostate cancer patients each, referred for 68Ga-PSMA-11 PET/CT because of biochemical recurrence after primary therapy, were compared: patients in group 1 (median prostate-specific antigen, 1.30 ng/mL) received no preparation before imaging, whereas patients in group 2 (median prostate-specific antigen, 0.82 ng/mL) were injected with 20 mg of furosemide and 500 mL of sodium chloride (NaCl 0.9%) immediately after tracer injection. The presence of local recurrence was assessed visually. In addition, the intensity of tracer accumulation in organs with physiologic tracer uptake was evaluated. Results: The detection rate of lesions judged positive for local recurrence was significantly higher in patients receiving furosemide than in patients without preparation: 56 cases (25.5%) versus 38 cases (17.3%), respectively (P = 0.048). Median maximum SUVs (SUVmax) of organs with physiologic uptake of 68Ga-PSMA-11 in groups 1 and 2 were urinary bladder (63.0 vs. 8.9), kidney (55.6 vs. 54.5), liver (9.9 vs. 9.4), spleen (11.2 vs. 11.9), small bowel (16.2 vs. 17.1), parotid gland (19.2 vs. 19.6), lacrimal gland (8.9 vs. 10.9), blood-pool activity (2.2 vs. 2.3), muscle (1.0 vs. 1.1), and bone (1.6 vs. 1.6). Apart from bladder activity, no significant reduction of tracer accumulation was found in the patient group receiving furosemide. Conclusion: Injection of 20 mg of furosemide at the time point of radiotracer administration significantly increases the detection rate of local recurrence in prostate cancer patients with biochemical recurrence referred for 68Ga-PSMA-11 PET/CT. As intensity of 68Ga-PSMA-11 uptake in organs with physiologic uptake is not significantly reduced, a negative impact of early furosemide injection on targeting properties and biodistribution of 68Ga-PSMA-11 seems unlikely.

Comparison of Early Imaging and Imaging 60 min Post-Injection after Forced Diuresis with Furosemide in the Assessment of Local Recurrence in Prostate Cancer Patients with Biochemical Recurrence Referred for 68Ga-PSMA-11 PET/CT

Background: 68Ga-PSMA-11 PET/CT is a promising method for the assessment of local recurrence (LR) in prostate cancer (PCa) patients. The aim of this study was to evaluate the diagnostic performance of early 68Ga-PSMA-11 PET imaging in comparison to 68Ga-PSMA-11 PET imaging 60 min post-injection (p.i.) in the detection of LR in patients with biochemical recurrence (BR) of prostate carcinoma. Materials and Methods: 190 image sets of patients with BR in PCa who underwent 68Ga-PSMA-11 PET/CT were assessed retrospectively (median prostate specific antigen (PSA) value, 0.70 ng/mL (range, 0.1–105.6 ng/mL)). Patients received an early static scan of the pelvic area (median, 248 s p.i. (range, 56–923 s)) and a whole-body scan 60 min p.i. (median, 64 min p.i. (range, 45–100 min)) with intravenous administration of 20 mg furosemide i.v. at the time of tracer application, followed by intravenous hydration with 500 mL of sodium chloride (NaCl 0.9%). Assessment was based on visual analysis and calculation of the maximum standardized uptake value (SUVmax) of the pathologic lesions present in the prostate fossa found in the early PET imaging and 60 min PET scans. The scans were characterized as negative, positive, or equivocal. The results were compared, and the combination of early and 60 min p.i. imaging was evaluated. Results: Image assessment resulted in 30 (15.8%) positive, 17 (8.9%) equivocal, and 143 (75.3%) negative findings in early scans, and 28 (14.7%) positive, 25 (13.2%) equivocal, and 137 (72.1%) negative findings of LR in 60 min p.i. images. For combined image analysis, 33 (17.4%) cases were positive and 20 (10.5%) were equivocal. There was no statistical significance between the number of positive (p = 0.815), negative (p = 0.327), and equivocal (p = 0.152) findings. Furthermore, the combination of both scans showed no statistically significant differences for the positive and negative findings (p = 0.063). The median SUVmax was 4.9 (range, 2.0–55.2) for positive lesions in the early scans and 8.0 (range, 2.1–139.9) in the scans 60 min p.i. The median SUVmax for bladder activity was 2.5 (range, 0.9–12.2) in the early scans and 8.2 (range, 1.8–27.6) in the scans 60 min p.i. Conclusion: Early static imaging additional to 68Ga-PSMA-11 PET images acquired 60 min p.i. has limited value in patients prepared with furosemide and hydration, and showed no statistically significant change in the detection rate (DR) of LR and the number of equivocal findings. Based on our results, in departments following a protocol with forced diuresis, including furosemide, additional early static imaging cannot be routinely recommended for the assessment of BR in PCa patients.

Pharmacokinetic studies of [68 Ga]Ga-PSMA-11 in patients with biochemical recurrence of prostate cancer: detection, differences in temporal distribution and kinetic modelling by tissue type

Purpose

[⁶⁸ Ga]Ga-PSMA-11 is a promising radiopharmaceutical for detecting tumour lesions in prostate cancer, but knowledge of the pharmacokinetics is limited. Dynamic PET-CT was performed to investigate the tumour detection and differences in temporal distribution, as well as in kinetic modelling of [⁶⁸ Ga]Ga-PSMA-11 by tissue type.

Methods

Dynamic PET-CT over the lower abdomen and static whole-body PET-CT 80–90 min p.i. from 142 patients with biochemical recurrence were retrospectively analysed. Detection rates were compared to PSA levels. Average time-activity curves were calculated from tumour lesions and normal tissue. A three-compartment model and non-compartment model were used to calculate tumour kinetics.

Results

Overall detection rate was 70.42%, and in patients with PSA > 0.4 ng/mL 76.67%. All tumour lesions presented the steepest standardised uptake value (SUV) incline in the first 7–8 min before decreasing to different degrees. Normal tissue presented with a low uptake, except for the bladder, which accumulated activity the steepest 15–16 min. p.i.. While all tumour lesions continuously increased, bone metastases showed the steepest decline, resulting in a significantly lower SUV than lymph node metastases (60 and 80–90 min). Transport rate from the blood and tracer binding and internalisation rate were lower in bone metastases. Heterogeneity (fractal dimension) and vascular density were significantly lower in bone metastases.

Conclusion

Even at low PSA between 0.51 and 0.99 ng/mL, detection rate was 57%. Dynamic imaging showed a time window in the first 10 min where tumour uptake is high, but no bladder activity is measured, aiding accuracy in distinction of local recurrence. Kinetic modelling provided additional information for tumour characterisation by tissue type.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05420-1.

[68Ga]Ga-P16-093 as a PSMA-Targeted PET Radiopharmaceutical for Detection of Cancer: Initial Evaluation and Comparison with [68Ga]Ga-PSMA-11 in Prostate Cancer Patients Presenting with Biochemical Recurrence

PURPOSE

This study was undertaken to evaluate radiation dosimetry for the prostate-specific membrane antigen targeted [⁶⁸Ga]Ga-P16-093 radiopharmaceutical, and to initially assess agent performance in positron emission tomography (PET) detection of the site of disease in prostate cancer patients presenting with biochemical recurrence.

PROCEDURES

Under IND 133,222 and an IRB-approved research protocol, we evaluated the biodistribution and pharmacokinetics of [⁶⁸Ga]Ga-P16-093 with serial PET imaging following intravenous administration to ten prostate cancer patients with biochemical recurrence. The recruited subjects were all patients in whom a recent [⁶⁸Ga]Ga-PSMA-11 PET/X-ray computed tomography (CT) exam had been independently performed under IND 131,806 to assist in decision-making with regard to their clinical care. Voided urine was collected from each subject at ~ 60 min and ~ 140 min post-[⁶⁸Ga]Ga-P16-093 injection and assayed for Ga-68 content. Following image segmentation to extract tissue time-activity curves and corresponding cumulated activity values, radiation dosimetry estimates were calculated using IDAC Dose 2.1. The prior [⁶⁸Ga]Ga-PSMA-11 PET/CT exam (whole-body PET imaging at 60 min post-injection, performed with contrast-enhanced diagnostic CT) served as a reference scan for comparison to the [⁶⁸Ga]Ga-P16-093 findings.

RESULTS

[⁶⁸Ga]Ga-P16-093 PET images at 60 min post-injection provided diagnostic information that appeared equivalent to the subject's prior [⁶⁸Ga]Ga-PSMA-11 scan. With both radiopharmaceuticals, sites of tumor recurrence were found in eight of the ten patients, identifying 16 lesions. The site of recurrence was not detected with either agent for the other two subjects. Bladder activity was consistently lower with [⁶⁸Ga]Ga-P16-093 than [⁶⁸Ga]Ga-PSMA-11. The kidneys, spleen, salivary glands, and liver receive the highest radiation exposure from [⁶⁸Ga]Ga-P16-093, with estimated doses of 1.7 × 10^-1, 6.7 × 10^-2, 6.5 × 10^-2, and 5.6 × 10^-2 mGy/MBq, respectively. The corresponding effective dose from [⁶⁸Ga]Ga-P16-093 is 2.3 × 10^-2 mSv/MBq.

CONCLUSIONS

[⁶⁸Ga]Ga-P16-093 provided diagnostic information that appeared equivalent to [⁶⁸Ga]Ga-PSMA-11 in this limited series of ten prostate cancer patients presenting with biochemical recurrence, with the kidneys found to be the critical organ. Diminished tracer appearance in the urine represents a potential advantage of [⁶⁸Ga]Ga-P16-093 over [⁶⁸Ga]Ga-PSMA-11 for detection of lesions in the pelvis.

68Ga-Prostate-specific membrane antigen (psma) positron emission tomography (pet) in prostate cancer: a systematic review and meta-analysis

Introduction:

Prostate cancer (PC) is the second most commonly diagnosed cancer in males. ⁶⁸Ga-PSMA PET/CT, a non-invasive diagnostic tool to evaluate PC with prostate-specific membrane antigen (PSMA) expression, has emerged as a more accurate alternative to assess disease staging. We aimed to identify predictors of positive ⁶⁸Ga-PSMA PET and the accuracy of this technique.

Materials and methods:

Diagnostic accuracy cross-sectional study with prospective and retrospective approaches. We performed a comprehensive literature search on PubMed, Cochrane Library, and Embase database in search of studies including PC patients submitted to radical prostatectomy or radiotherapy with curative intent and presented biochemical recurrence following ASTRO 1996 criteria. A total of 35 studies involving 3910 patients submitted to 68-Ga-PSMA PET were included and independently assessed by two authors: 8 studies on diagnosis, four on staging, and 23 studies on restaging purposes. The significance level was α=0.05.

Results:

pooled sensitivity and specificity were 0.90 (0.86-0.93) and 0.90 (0.82-0.96), respectively, for diagnostic purposes; as for staging, pooled sensitivity and specificity were 0.93 (0.86-0.98) and 0.96 (0.92-0.99), respectively. In the restaging scenario, pooled sensitivity and specificity were 0.76 (0.74-0.78) and 0.45 (0.27-0.58), respectively, considering the identification of prostate cancer in each described situation. We also obtained specificity and sensitivity results for PSA subdivisions.

Conclusion:

⁶⁸Ga-PSMA PET provides higher sensitivity and specificity than traditional imaging for prostate cancer.

PSMA-targeted Radiotracers versus 18F Fluciclovine for the Detection of Prostate Cancer Biochemical Recurrence after Definitive Therapy: A Systematic Review and Meta-Analysis

Background National guidelines endorse fluorine 18 (¹⁸F) fluciclovine PET/CT for the detection of prostate cancer (PCa) in men with biochemically recurrent PCa. The comparative performance between fluciclovine and gallium 68 or ¹⁸F prostate-specific membrane antigen (PSMA) PET/CT, a newer examination, is unclear. Purpose To compare the detection of biochemical recurrence using fluciclovine versus PSMA-targeted radiotracers in patients with a prostate-specific antigen (PSA) level less than 2 ng/mL. Materials and Methods With use of the Preferred Reporting Items for a Systematic Review and Meta-Analysis of Diagnostic Test Accuracy, or PRISMA-DTA, guidelines, a systematic review of PubMed and EMBASE databases between 2012 and 2019 was performed. Studies of fluciclovine PET/CT or PSMA PET/CT in biochemical recurrence were identified. PSA levels, clinical data, and reference standards were obtained when available. A random-effects model was applied to pooled estimates and 95% confidence intervals (CIs) around the prevalence of a positive examination, stratified according to PSA tier. Results Quantitative analysis included 482 patients (median age, 67 years; interquartile range, 67-67 years) in six fluciclovine studies and 3217 patients (median age, 68 years; interquartile range, 67-70 years) in 38 PSMA studies. Pooled detection rates for PSMA and fluciclovine were 45% (95% CI: 38%, 52%) and 37% (95% CI: 25%, 49%), respectively, for a PSA level less than 0.5 ng/mL (P = .46); 59% (95% CI: 52%, 66%) and 48% (95% CI: 34%, 61%) for a PSA level of 0.5-0.9 ng/mL (P = .19); and 80% (95% CI: 75%, 85%) and 62% (95% CI: 54%, 70%) for a PSA level of 1.0-1.9 ng/mL (P = .01). A reference standard was positive in 703 of 735 patients (96%) in the PSMA cohort and 247of 256 (97%) in the fluciclovine cohort. Conclusion Patient-level detection rates for biochemically recurrent prostate cancer were greater for prostate-specific membrane antigen-targeted radiotracers than fluciclovine for prostate specific antigen levels of 1.0-1.9 ng/mL. © RSNA, 2020 Online supplemental material is available for this article.

Impact of forced diuresis with furosemide and hydration on the halo artefact and intensity of tracer accumulation in the urinary bladder and kidneys on [68Ga]Ga-PSMA-11-PET/CT in the evaluation of prostate cancer patients

PURPOSE

to assess the influence of intravenous hydration and forced diuresis with furosemide in two different dosages (20 vs 40 mg) on the intensity of tracer accumulation in the urinary collection system and on the occurrence of halo artefact surrounding the urinary bladder and kidneys in [⁶⁸Ga]Ga-PSMA-11-PET/CT scans.

MATERIALS AND METHODS

Comparison of four groups with 50 patients each, receiving different preparation prior to [⁶⁸Ga]Ga-PSMA-11-PET/CT. Group one, no preparation. Group two, 500 ml sodium chloride administered immediately after tracer injection. Group three, 500 ml sodium chloride and injection of 20 mg furosemide immediately after tracer administration. Group four, 500 ml sodium chloride and injection of 40 mg furosemide immediately after tracer injection. Images were judged visually whether halo artefact was present; semiquantitative measurements were performed with standardised uptake value (SUV).

RESULTS

Halo artefact of the urinary bladder was present in twelve patients without preparation, in eight patients receiving only sodium chloride, in one patient injected with 20 mg furosemide/sodium chloride and in two patients receiving 40 mg furosemide/sodium chloride, showing a median SUV_mean in the bladder of 45.8, 14.4, 4.6 and 5.8, respectively. Differences between patient group without preparation and the two groups with furosemide/sodium chloride were statistically significant. Patient groups receiving 20 mg furosemide and 40 mg furosemide did not differ significantly. Renal halo artefacts were observed in 15 patients of group one, in ten patients of group two, in 14 patients of group three and in 14 patients of group four, with corresponding median SUV_mean values of 33.9, 32.0, 37.8 and 30.4 (no statistically significant differences).

CONCLUSION

Performing [⁶⁸Ga]Ga-PSMA-11-PET/CT, intravenous injection of 20-mg furosemide and 500-ml sodium chloride significantly reduces the number of bladder halo artefacts and intensity of tracer accumulation in the urinary bladder. A total of 40 mg furosemide does not further improve results.

Combined Early and Late [68Ga]PSMA-HBED-CC PET Scans Improve Lesion Detectability in Biochemical Recurrence of Prostate Cancer with Low PSA Levels

PURPOSE

Our aim was to evaluate the benefit of early (1 h post-injection (p.i.)) and late (3 h p.i.) [⁶⁸Ga]PSMA-HBED-CC positron emission tomography (PET)/x-ray computed tomography (CT) imaging for detection of biochemical recurrence (BCR) of prostate cancer (PCa).

PROCEDURES

Seventy patients with BCR of the PCa and prostate-specific antigen (PSA) levels of less than 2.0 μg/l were subjected to [⁶⁸Ga]PSMA-HBED-CC PET (mean injected activity 180 MBq). While early imaging contained whole body scans, late imaging was confined to the pelvis and the lower abdomen. Uptake in suspicious lesions was analyzed by peak and maximum standardized uptake values (SUV_peak/max). Tumor-to-background ratios were calculated for all lesions in which the liver served as reference organ. The Wilcoxon matched-pair signed-rank test was used to compare the uptake in suspicious lesions between early and late imaging. Follow-up data were used to validate the existence of the additionally detected lesions.

RESULTS

Forty-four of the 70 patients thus examined were interpreted as PSMA-positive in early and/or late scans while 26 remained without suspicion of PSMA tracer uptake. A total of 70 suspicious lesions were analyzed. Ten tumor-suspicious lesions from seven different patients were better or exclusively visible in the late measurements while three tumor-suspicious lesions from three different patients were better or exclusively visible in the early images. A validation by follow-up data was possible for 11 of these 13 additionally detected lesions. In direct comparison between early and late imaging, the mean SUV_max in PSMA-positive lesions was 74 % higher (p < 0.001) and the mean SUV_peak was 36 % higher (p = 0.001) in the late scans. The SUV_mean in the reference regions was decreasing in the late measurements, whereas the mean TBR increased by a factor of 3 (p < 0.001). Taking confirmed lesions only into account, we estimated a 10 % gain in additionally detected PSMA-positive lesions (7/70) within the patient cohort.

CONCLUSIONS

The time period between injection and data acquisition influences the detection rate of [⁶⁸Ga]PSMA-HBED-CC PET/CT. In biochemical recurrence with low PSA levels, late [⁶⁸Ga]PSMA-HBED-CC PET/CT imaging offers frequent advantages with regard to lesion contrast.

Factors Predicting Metastatic Disease in 68Ga-PSMA-11 PET-Positive Osseous Lesions in Prostate Cancer

Bone is the most common site of distant metastatic spread in prostate adenocarcinoma. Prostate-specific membrane antigen (PSMA) uptake has been described in both benign and malignant bone lesions, which can lead to false-positive findings on ⁶⁸Ga-PSMA-11 PET. The purpose of this study was to evaluate the diagnostic accuracy of ⁶⁸Ga-PSMA-11 PET for osseous prostate cancer metastases and improve bone uptake interpretation using semiquantitative metrics. Methods: Fifty-six prostate cancer patients (18 before prostatectomy and 38 with biochemical recurrence) who underwent ⁶⁸Ga-PSMA-11 PET/MRI or PET/CT examinations with osseous PSMA-ligand uptake were included in the study. Medical records were reviewed retrospectively by board-certified nuclear radiologists to determine true or false positivity based on a composite endpoint. For each avid osseous lesion, we measured biologic volume; size; PSMA Reporting and Data System (RADS) rating; SUV_max; and ratio of lesion SUV_max to liver, blood pool, and background bone SUV_max Differences between benign and malignant lesions were evaluated for statistical significance, and cutoffs for these parameters were determined to maximize diagnostic accuracy. Results: Among 56 participants, 13 (22.8%) had false-positive osseous ⁶⁸Ga-PSMA-11 findings and 43 (76.8%) had true-positive osseous ⁶⁸Ga-PSMA-11 findings. Twenty-two patients (39%) had 1 osseous lesion, 18 (32%) had 2-4 lesions, and 16 (29%) had 5 or more lesions. Cutoffs resulting in statistically significant (P < 0.005) differences between benign and malignant lesions were a PSMA RADS rating of at least 4, an SUV_max of at least 4.1, and SUV_max ratios of at least 2.11 for lesion to blood pool, at least 0.55 for lesion to liver, and at least 4.4 for lesion to bone. These measurements corresponded to a lesion-based ⁶⁸Ga-PSMA-11 PET lesion detection rate of 80%, 93%, 89%, 21%, and 89%, respectively, for malignancy, and a specificity of 73%, 73%, 73%, 93%, and 60%, respectively. Conclusion: PSMA RADS rating, SUV_max, and SUV_max ratio for lesion to blood pool can help differentiate benign from malignant lesions on ⁶⁸Ga-PSMA-11 PET. An SUV_max ratio of more than 2.2 for lesion to blood pool is a reasonable parameter to support image interpretation and presented a superior lesion detection rate and specificity when compared with visual interpretation by PSMA RADS. These parameters hold clinical value by improving diagnostic accuracy for metastatic prostate cancer on ⁶⁸Ga-PSMA-11 PET/MRI and PET/CT.

Role of Early PET/CT Imaging with 68Ga-PSMA in Staging and Restaging of Prostate Cancer

Ga-68 Prostate-Specific Membrane Antigen PET/CT is a new tool for the assessment of prostate cancer. Standard imaging time is 60 minutes post injection of radiotracer. At 60 minutes, there is physiologic accumulation of radiotracer in the urinary bladder which may cause some lesions in its vicinity to be obscured. Our aim is to determine if early imaging at 3 minutes in addition to standard imaging at 60 minutes can improve the detection of PSMA-avid lesions. A retrospective review of 167 consecutive patients was conducted. Overall, 115 patients (68.9%) were ruled to have prostate cancer based on imaging as seen on early or standard PET/CT images. In 106/115 (64%), the lesions were detected on both early and standard imaging; in 8/115 (6.9%), the lesions were only detected on early imaging; in 1/115 (0.6%) the lesion was detected only on standard imaging. The addition of early imaging significantly improved the overall detection rate of PSMA-avid lesions (p = 0.039). The ratio of patients with lesions detected on early imaging but not on standard imaging in restaging group was 7/88 and was higher than that in staging group 1/79 (p = 0.043). We recommend early imaging in addition to the standard imaging in Ga-68 PSMA PET/CT, particularly in patients presenting for restaging of prostate cancer.

Multiphasic 68Ga-PSMA PET/CT in the Detection of Early Recurrence in Prostate Cancer Patients with a PSA Level of Less Than 1 ng/mL: A Prospective Study of 135 Patients

The main objective of this prospective study was to determine the impact of multiphasic acquisition of ⁶⁸Ga-PSMA PET/CT in the detection of recurrent prostate cancer in the early stage of biochemical recurrence with a prostate-specific antigen (PSA) level of less than 1 ng/mL. Also, ⁶⁸Ga-PSMA PET/CT positivity was correlated with clinical parameters for the assessment of predictive markers. Methods: A prospective monocentric study was conducted on 135 prostate cancer patients with biochemical recurrence and a PSA level of less than 1 ng/mL. All patients had undergone initial prostatectomy, with additional radiation therapy in 19.3% of patients and androgen-deprivation therapy in 7.4%. The patients underwent dynamic acquisitions from the prostate bed (1-8 min after injection), standard whole-body acquisitions (60 min after injection), and limited-bed-position delayed acquisitions (120-150 min after injection). The studies were reviewed by 2 board-certified nuclear medicine specialists, independently. A combination of visual and semiquantitative analyses and correlation with morphologic (e.g., MRI) or clinical follow-up findings was used for the final interpretation of lesions as benign or malignant. ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT positivity was also correlated with primary clinical findings. Results: Incorporating the information from all phases, we were able to detect 116 lesions in 49.6% of patients (22 local recurrences, 63 lymph nodes, and 31 distant metastases). The detection rates were 31.8%, 44.9%, and 71.4% for PSA < 0.2 ng/mL, 0.2 ≤ PSA < 0.5, and 0.5 ≤ PSA < 1, respectively. Additional dynamic or delayed phases resulted in better determination of equivocal lesions and a higher diagnostic performance in 25.9% of patients. Stand-alone dynamic and delayed images led to better interpretation of equivocal findings in the prostate bed (31.4%) and in other lesions (lymph node or bone) (20%), respectively. Conclusion: ⁶⁸Ga-PSMA PET/CT showed promise for early detection of recurrent disease in patients with a PSA level of 0.5-1.0 ng/mL. However, it showed limited value in patients with a PSA level of less than 0.5 ng/mL. Multiphasic ⁶⁸Ga-PSMA PET/CT led to a better determination of equivocal findings. Although dynamic images may provide helpful information for assessment of the prostate bed, delayed acquisitions seem to have a greater impact in clarifying equivocal findings.

68Ga-PSMA PET/CT for monitoring response to 177Lu-PSMA-617 radioligand therapy in patients with metastatic castration-resistant prostate cancer

PURPOSE

To evaluate the use of ⁶⁸Ga-PSMA PET/CT for monitoring response to ¹⁷⁷Lu-617 PSMA radioligand therapy in patients with metastatic castrate-resistant prostate cancer (mCRPC).

METHODS

Patients from the University Hospital Bonn and the University Hospital Aachen were retrospectively reviewed for this study. We included 48 patients with mCRPC who were treated with ¹⁷⁷Lu-PSMA-617 and whose records included ⁶⁸Ga-PSMA PET/CT imaging before the first and after the third or fourth treatment cycle. A treatment response based on ⁶⁸Ga-PSMA PET/CT was defined according to a modified version of the PERCIST criteria. A decline in PSA level of ≥50% was considered the reference standard. The sensitivity, specificity, positive and negative predictive values, and ROC curves were calculated, and patient survival times in relation to the PET results were also analysed.

RESULTS

⁶⁸Ga-PSMA PET/CT had a sensitivity of about 85% and a specificity of between 55% and 65%. The negative and positive predictive values ranged between 70% and 78%. The fitted ROC area was 0.70. The survival time was about 19.6 months in patients with a treatment response, while nonresponders had a survival time of about 15.9 months. However, this difference between the groups was not statistically significant.

CONCLUSION

Our results indicate that ⁶⁸Ga-PSMA PET/CT could be a useful tool for the evaluation of response to ¹⁷⁷Lu-PSMA-617 radioligand therapy within a theranostic framework.

Efficacy of early imaging with 68Ga-PSMA-I&T in the discrimination of pelvic lesions in prostate cancer patients

OBJECTIVE

⁶⁸Ga-PSMA-uptake shows accumulation in the malignant lesions of prostate cancer patients as early as 5min p.i. Studies indicate the value of adding an early image of the pelvis to the imaging protocol of ⁶⁸Ga-PSMA-11 PET/CT scan showed contradictory results. In this study we planned to assess the significance of an additional early imaging in ⁶⁸Ga-PSMA-I&T PET/CT imaging in prostate cancer patients.

MATERIALS AND METHODS

A total of 35 prostate cancer patients referred to ⁶⁸Ga-PSMA-I&T PET/CT imaging for restaging of the disease due to suspicion of relapse after definitive therapy were enrolled. First an early static pelvic image was obtained at a maximum of 300s following injection of the radiotracer. Sixty minutes postinjection a whole-body PET/CT scan was conducted with an emission time of 3min per bed position. The lesions which were categorized as local recurrence, bone lesion and lymph node metástasis in the early images, were compared with the late images in terms of number of lesions detected and SUVmax values.

RESULTS

⁶⁸Ga-PSMA-I&T PET/CT was positive in 23 of 35 patients (65.7%). A pathological uptake was observed in the prostatic bed site, in the pelvic lymph nodes, and in the bones in 17 patients (48.5%), 12 patients (34.2%), and 13 patients (37.1%), respectively. In one patient, focal pathological increased uptake in the prostatic bed with a SUVmax value of 5.8 was detected but this lesion disappeared in the late images. The average SUVmax values of the lesions in the prostatic bed were 13.7±12.1 versus 26.3±23.8 in the 5min and 60min studies respectively (p<0.001). In one patient, the pathological uptake in the lymph node in the early study cleared in the late study, whereas in another accumulation of activity was detected in a pelvic lymph node in the late study, while there was no lymph node detected in the early study. The average SUVmax values of the lymph nodes were 12.1±8.8 versus 26.3±22.6 in the 5min and 60min studies respectively (p<0.001). The average SUVmax values of the bone lesions were 11.4±6.9 versus 15±10.7 in the 5min and 60min studies respectively.

CONCLUSION

Our study is the first in the literature to evaluate the impact of adding an early static pelvic image to the ⁶⁸Ga-PSMA-I&T scan, in the detection rate of the lesions. Although there was no marked discordance between the 2sets of images, the addition of an early image to the imaging protocol of ⁶⁸Ga-PSMA-I&T scan would increase the efficacy of detection of malignant lesions in the pelvis, which might show rapid clearance and has the risk of being masked by the urinary system activity.

Prostate-specific membrane antigen positron emission tomography in the management of recurrent prostate cancer

INTRODUCTION

There is an unmet clinical need for early, accurate imaging of recurrent prostate cancer to improve patient outcomes. Staging, by conventional bone scintigraphy and CT have become outdated. 68Ga-PSMA PET/CT imaging in this setting has developed rapidly, with widespread International adoption in line with evidence-based guidelines in this group of patients.

SOURCES OF DATA

A PubMed search of English language articles was performed using following keywords: PSMA, PET/CT, biochemical recurrence, prostate cancer. The search revealed 85 articles, of which 75 were original; 70 of these involved use of the most widely available type of PSMA tracer (HBED). The review also relied on the clinical experience of reporting over 1000 PSMA PET/CT studies at a major tertiary referral centre for uro-oncology, with the majority of cases having been performed in the biochemical recurrence setting from 2015 to 2018.

AREAS OF AGREEMENT

68Ga-PSMA PET is a game changer and superior to choline PET and other established tracers which have been used in prostate cancer evaluation. Detection of recurrence at the prostate bed remains challenging due to bladder and urethral tracer accumulation. The main strength of PSMA PET/CT is its ability to identify small (<8 mm) pathological lymph nodes, upstaging nodal status in up to two-thirds of cases. Additionally, PSMA PET/CT, detects bone and bone marrow metastases missed by conventional bone and CT imaging. Thus, PSMA PET/CT has major impact on patient management, with studies reporting overall changes in 39-76% of cases.

AREAS OF CONTROVERSY

Controversy exists regarding patient access and NHS affordability of PSMA PET/CT imaging. Currently, no reimbursement is available under the NHS tariff system. The cost outlay for tertiary hospital linked PET centres ranges from £150-170 K. Large referral volumes, and technical advances in manufacturing process will make this tracer cost neutral and similar to the current funded, but less sensitive, choline PET. Current NICE guidelines for prostate cancer management do not include a recommendation on when PSMA PET/CT should be used and this is likely to remain the case in the next revision, due in 2019.

GROWING POINTS

Although PSMA PET/CT imaging results in significant management change, there is a need for high quality economic evaluation and cost analysis for this modality. Lack of this data will result in poor adoption of this technique and thus limit patient access. Furthermore, it is hoped that future tracers will become even more sensitive and identify disease at earlier thresholds.

AREAS TIMELY FOR DEVELOPING RESEARCH

Well-designed clinical trials with consideration of the health economic benefit of using PSMA PET/CT will be essential to provide a basis for entry into guidelines such as NICE and to provide a rationale for reimbursement.

PSMA-PET based radiotherapy: a review of initial experiences, survey on current practice and future perspectives

⁶⁸Gallium prostate specific membrane antigen (PSMA) ligand positron emission tomography (PET) is an increasingly used imaging modality in prostate cancer, especially in cases of tumor recurrence after curative intended therapy. Owed to the novelty of the PSMA-targeting tracers, clinical evidence on the value of PSMA-PET is moderate but rapidly increasing. State of the art imaging is pivotal for radiotherapy treatment planning as it may affect dose prescription, target delineation and use of concomitant therapy.

This review summarizes the evidence on PSMA-PET imaging from a radiation oncologist’s point of view. Additionally a short survey containing twelve examples of patients and 6 additional questions was performed in seven mayor academic centers with experience in PSMA ligand imaging and the findings are reported here.

The role of 68Ga-PSMA PET/CT scan in biochemical recurrence after primary treatment for prostate cancer: a systematic review of the literature

INTRODUCTION

Recurrence after primary treatment of prostate cancer is one of the major challenges facing urologists. Biochemical recurrence is not rare and occurs in up to one third of the patients undergoing radical prostatectomy. Management of biochemical recurrence is tailored according to the site and the burden of recurrence. Therefore, developing an imaging technique to early detect recurrent lesions represents an urgent need. Positron emission tomography (PET) of 68Ga-labelled prostate-specific membrane antigen (68Ga-PSMA) is an emerging imaging modality that seems to be a promising tool with capability to localize recurrent prostate cancer. A systematic review of literature was done to evaluate the role of 68Ga-PSMA PET/CT scan in patients with recurrent prostate cancer after primary radical treatment.

EVIDENCE ACQUISITION

A systematic and comprehensive review of literature was performed in September 2017 analyzing the MEDLINE and Cochrane Library following the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. The following key terms were used for the search "PSMA," "prostate-specific membrane antigen," "positron emission tomography," "PET," "recurrent," "prostate cancer," "prostate neoplasm," "prostate malignancy," and "68Ga." Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool.

EVIDENCE SYNTHESIS

Thirty-seven articles met our inclusion criteria and were included in the analysis of this systematic review. Of the 37 articles selected for analysis only four studies were prospective. The overall detection rate of 68Ga-PSMA PET scan ranged from 47% up to 96.6%. The main advantage of this imaging technique is its relatively high detection rates at low serum PSA levels below 0.5 ng/mL (ranging from 11.1% to 75%). Higher serum PSA level was strongly associated with increased positivity on 68Ga-PSMA PET scan. 68Ga-PSMA PET scan was found superior to conventional imaging techniques (CT and MRI) in this setting of patients and even it seems to outperform choline-based PET scan. This technique provided significant changes in the therapeutic management of 28.6-87.1% of patients.

CONCLUSIONS

After biochemical recurrence, the primary goal is to locate the recurrent lesions' site. 68Ga-PSMA PET/CT seems to be effective in identifying recurrence localization also for very low levels of PSA (<0.5 ng/mL) thus permitting to choose the best therapeutic strategy as early as possible. However, data available cannot be considered exhaustive and prospective randomized trials are needed.

Role of Early Dynamic Positron Emission Tomography/Computed Tomography with 68Ga-prostate-specific Membrane Antigen-HBED-CC in Patients with Adenocarcinoma Prostate: Initial Results

RATIONALE

Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) is widely used for imaging of prostate cancer (PC) nowadays. However, appearance of bladder activity many a times hampers lesion detection vis-a-vis primary as well as regional nodes. We aimed to assess if early dynamic PET/CT can be a potential solution to this issue.

METHODOLOGY

A total of 15 biopsy-proven PC patients who were referred to our department for 68Ga-PSMA PET/CT for staging/restaging were prospectively studied. Dynamic PET/CT was done with on table intravenous injection of 2-3 mCi (74-111 MBq) of the radiotracer. Dynamic images were acquired over the pelvis with a frame time of 1 min for 10 min. Static images of 2 min per bed position were acquired between 45 and 60 min after injection. A 3D volume of interest was plotted on the primary lesion, involved nodes if any, pelvic bones at involved and uninvolved sites, gluteal muscles, and bladder.

RESULTS

Six patients were referred for staging and 9 for restaging. Mean age of 15 patients was 66.7 years, median prostate-specific antigen level was 17.25 ng/ml (Range 0.05-218), mean Gleason score was 8. All patients showed high target to nontarget ratio in the early dynamic images comparable to that seen on the delayed images in different sites (prostatic primary: n = 15 patients; lymph nodes: n = 10 patients; bone: n = 5 patients). All pathologic lesions showed tracer uptake within the first 3 min and reached maximum uptake during the dynamic study in last 3 min, indicating an increasing uptake pattern, whereas urinary bladder (UB) activity was insignificant within the first 3 min of dynamic imaging in all patients, reached maximum during last 3 min. SUVmax was significantly higher in primary lesions in the first 4 min compared to UB accumulation. Static images showed more tracer accumulation than dynamic images in primary, nodal, and bony lesions. However, all regional nodes seen on delayed static imaging also showed uptake on dynamic imaging.

CONCLUSION

Early dynamic imaging 68Ga-PSMA PET/CT can demarcate the primary tumor clearly due to nonaccumulation of bladder activity and appears to have comparable efficacy in detecting pelvic nodal sites as delayed imaging.

68Ga-PSMA PET/CT in prostate cancer

Positron emission tomography/computed tomography (PET/CT) with ⁶⁸Ga-PSMA is a non-invasive diagnostic technique to image prostate cancer with increased prostate-specific membrane antigen (PSMA) expression. PSMA is a transmembrane protein present in all prostatic tissues. Increased PSMA expression is seen in several malignancies, although prostate cancer is the tumour where it presents higher concentrations. Almost all prostate adenocarcinomas show PSMA expression in most of lesions, primary and metastatic. Immunohistochemistry has demonstrated that the expression of PSMA increases in patients with de-differentiated, metastatic or hormone-refractory tumours. Moreover, the expression level of PSMA has a prognostic value for disease outcome. PET measures the three-dimensional distribution of ⁶⁸Ga-PSMA, producing semi-quantitative images that allow for non-invasive assessment of PSMA expression.