Assessment of volumetric parameters derived from 68Ga-PSMA PET/CT in prostate cancer patients with biochemical recurrence: an institutional experience

Whole-body tumour burden on [18F]DCFPyL PET/CT in biochemical recurrence of prostate cancer: association with tumour biology and PSA kinetics

PURPOSE

The objective was to assess the association between molecular imaging (mi) variables on [18F]DCFPyL-PET/CT with clinical and disease characteristics and prostate specific antigen (PSA) related variables in patients with biochemical recurrence of prostate cancer (BRPC).

MATERIAL AND METHODS

We analysed patients with BRPC after radical treatment. We obtained clinical and PSA variables: International Society of Urology Pathology (ISUP) grade group, European Association of Urology (EAU) risk classification, PSA (PSA≤1ng/ml, 12), PSA doubling time (PSAdt) and PSA velocity (PSAvel). All PET/CT scans were reviewed with the assistance of automated Prostate Molecular Imaging Standardized Evaluation (aPROMISE) software and lesions' segmentation in positive scans was performed using this platform. Standardized uptake value (SUV) derived variables; tumour burden variables [whole-body tumour volume (wbTV), whole-body tumour lesion activity (wbTLA) and whole-body mi PSMA (wbPSMA)] and miTNM staging were obtained. Cut-off of PSA and kinetics able to predict PET/CT results were obtained. Associations between disease and mi variables were analysed using ANOVA, Kruskal-Wallis and Spearman's correlation tests. Multivariate analysis was also performed.

RESULTS

Two hundred and seventy-five patients were studied. [18F]DCFPyL-PET/CT were positive in 165/275 patients. In multivariate analysis, moment of biochemical recurrence, ISUP group, PSA level and PSAvel showed significant association with the detection rate. miTNM showed significant association with PSA level (p<0.001) and kinetics (p<0.001), being higher in patients with metastatic disease. Both PSA and PSAvel showed moderate correlation with wbTV, wbTLA and wbPSMA (p<0.001). A weak correlation with SUVs was found. Mean wbTV, wbTLA and wbPSMA values were significantly higher in PSA > 2ng/ml, PSAdt ≤ 6 months and PSAvel ≥ 0.2ng/ml/month groups. Also, wbTV (p=0.039) and wbPSMA (p=0.020) were significantly higher in patients with ISUP grade group 5. PSA and PSAvel cut-offs (1.15 ng/ml and 0.065 ng/ml/month) were significantly associated with a positive PET/CT.

CONCLUSION

Higher PSA values, unfavourable PSA kinetics and ISUP grade group 5 were robust predictive variables of larger tumour burden variables on [18F]DCFPyL PET/CT assessed by aPROMISE platform.

The image quality and feasibility of solitary delayed [68 Ga]Ga-PSMA-11 PET/CT using long field-of-view scanning in patients with prostate cancer

BACKGROUND

Previous studies have demonstrated that delayed [68 Ga]Ga-PSMA PET/CT imaging improves lesion detection compared to early [68 Ga]Ga-PSMA PET/CT in patients with prostate cancer. However, the sole use of delayed [68 Ga]Ga-PSMA PET/CT has been limited due to the insufficient number of photons obtained with standard PET/CT scanners. The combination of early and delayed [68 Ga]Ga-PSMA standard PET/CT may be considered, and it is challenging to incorporate into a high-demand clinical setting. Long field-of-view (LFOV) PET/CT scanners have higher sensitivity compared to standard PET/CT. However, it remains unknown whether the image quality of solitary delayed [68 Ga]Ga-PSMA LFOV PET/CT imaging is adequate to satisfy clinical diagnostic requirements. Therefore, the purpose of this study was to evaluate the image quality of delayed [68 Ga]Ga-PSMA LFOV PET/CT and examine the feasibility of utilizing delayed [68 Ga]Ga-PSMA LFOV PET/CT imaging alone in patients with prostate cancer.

METHODS

The study sample consisted of 56 prostate cancer patients who underwent [68 Ga]Ga-PSMA-11 LFOV PET/CT scanning between December 2020 and July 2021. All patients were subjected to early LFOV PET/CT imaging at 1-h post-injection as well as delayed LFOV PET/CT imaging at 3-h post-injection using [68 Ga]Ga-PSMA-11. The image quality and diagnostic efficiency of solitary delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT imaging was analyzed.

RESULTS

The results showed that delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT yielded satisfactory image quality that fulfilled clinical diagnostic benchmarks. Compared to early imaging, delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT demonstrated heightened lesion SUVmax values (11.0 [2.3-193.6] vs. 7.0 [2.0-124.3], P < 0.001) and superior tumor-to-background ratios (3.3 [0.5-62.2] vs. 1.7 [0.3-30.7], P < 0.001). Additionally, delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT detected supplementary lesions in 14 patients (25%) compared to early imaging, resulting in modifications to disease staging and management plans.

CONCLUSIONS

In summary, the findings indicate that the image quality of delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT is satisfactory for meeting clinical diagnostic prerequisites. The use of solitary delayed [68 Ga]Ga-PSMA-11 LFOV PET/CT imaging in prostate cancer simplifies the examination protocol and improves patient compliance, compared to [68 Ga]Ga-PSMA-11 standard PET/CT which necessitates both early and delayed imaging.

The prognostic value of 18F-PSMA-1007 PET/CT in predicting pathological upgrading of newly diagnosed prostate cancer from systematic biopsy to radical prostatectomy

Objective

This study aimed to evaluate predictors for upgrading of newly diagnosed prostate cancer from systematic biopsy (SB) to radical prostatectomy (RP) using fluorine-18 prostate-specific membrane antigen 1007 (¹⁸F-PSMA-1007) positron emission tomography/computed tomography (PET/CT) and association with clinical parameters.

Materials and methods

We retrospectively collected data from biopsy-confirmed prostate cancer (PCa) patients who underwent ¹⁸F-PSMA-1007 PET/CT prior to RP from July 2019 and October 2022. Imaging characteristics derived from ¹⁸F-PSMA-1007 PET/CT and clinical parameters were compared in patients of pathological upgrading and concordance subgroups. Univariable and multivariable logistic regressions were performed to analyze factors predicting histopathological upgrading from SB to RP specimens. Discrimination ability of independent predictors was further evaluated by receiver operating characteristic (ROC) analysis with corresponding area under the curve (AUC).

Results

Pathological upgrading occurred in 26.97% (41/152) PCa patients, and 23.03% (35/152) of all patients experienced pathological downgrading. Concordance rate reached 50% (76/152). International Society of Urological Pathology grade group (ISUP GG) 1(77.78%) and ISUP GG 2 (65.22%) biopsies were related with the highest rate of upgrading. Multivariable logistic regression analyses showed that prostate volume (OR= 0.933; 95% CI, 0.887-0.982; p = 0.008), ISUP GG 1 vs. 4 (OR= 13.856; 95% CI: 2.467-77.831; p = 0.003), and total uptake of PSMA-avid lesions (PSMA-TL) (OR = 1.003; 95% CI, 1.000-1.006; p = 0.029) were found to be independent risk factors of pathological upgrading after RP. The AUCs and corresponding sensitivity and specificity of the independent predictors of synthesis for upgrading were 0.839, 78.00%, and 83.30% respectively, which showed good discrimination capacity.

Conclusion

¹⁸F-PSMA-1007 PET/CT may help to predict pathological upgrading between biopsy and RP specimens, particularly for ISUP GG 1 and ISUP GG 2 patients with higher PSMA-TL and smaller prostate volume.

Head-to-head comparisons of [68Ga]Ga-PSMA-11 PET/CT, multiparametric MRI, and prostate-specific antigen for the evaluation of therapeutic responses to neoadjuvant chemohormonal therapy in high-risk non-metastatic prostate cancer patients: a prospective study

PURPOSE

The optimal tool to evaluate the tumour therapeutic responses to neoadjuvant chemohormonal therapy (NCHT) in patients with high-risk non-metastatic prostate cancer (PCa) remains uncertain. We compared the role of [⁶⁸Ga]-labeled prostate-specific membrane antigen (PSMA)-11 positron emission tomography/computerized tomography ([⁶⁸Ga]Ga-PSMA-11 PET/CT), multiparametric MRI (mpMRI), and prostate-specific antigen (PSA) and assessed the practical value of the recent European Association of Urology and European Association of Nuclear Medicine (EAU/EANM) recommended criteria of PSMA PET/CT to evaluate the therapeutic responses to NCHT in patients with high-risk non-metastatic PCa.

METHODS

This prospective study included 72 high-risk non-metastatic PCa patients receiving NCHT followed by radical prostatectomy from June 2021 to March 2022. PSA testing, [⁶⁸Ga]Ga-PSMA-11 PET/CT, and mpMRI scanning were conducted in all patients before and after NCHT. Therapeutic responses to NCHT were evaluated with PSA, RECIST 1.1, PERCIST 1.0, and EAU/EANM recommended criteria. Postoperative pathological results were considered the reference standard. A favourable pathological response was defined as pathologic complete remission (pCR) or minimal residual disease (MRD). Diagnostic accuracy was assessed by sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value (PPV), negative predictive value (NPV), and Cohen's kappa index. Logistic regression analysis was used to determine the independent predictive value of [⁶⁸Ga]Ga-PSMA-11 PET/CT-derived parameters.

RESULTS

All cases experienced a marked decrease in PSA levels after NCHT. Twenty-four (33.33%) cases experienced a favourable pathological response, including five (6.94%) cases of pCR and 19 (26.39%) cases of MRD. According to the results of [⁶⁸Ga]Ga-PSMA-11 PET/CT, EAU/EANM recommended criteria indicated that 20 (27.78%) cases had a CR, whereas PERCIST 1.0 criteria indicated that 23 (31.94%) cases had a CR. There was a strong association between EAU/EANM recommended criteria and PERCIST 1.0 criteria (Pearson's R=0.857). The sensitivity (75.00%, 79.17% vs. 58.33%, 58.33%), specificity (95.83%, 91.67% vs. 83.33%, 68.75%), PLR (18.00, 9.50 vs. 3.50, 1.87), NLR (0.26, 0.23 vs. 0.50, 0.61), PPV (90.0%, 82.6% vs. 63.6%, 48.3%), and NPV (88.5%, 89.8% vs. 80.0%, 76.7%) of [⁶⁸Ga]Ga-PSMA-11 PET/CT (including EAU/EANM recommended criteria and PERCIST 1.0 criteria) to predict favourable pathological responses were all superior to those of mpMRI and nadir PSA. The kappa index to predict a favourable pathological response was 0.257 for PSA, 0.426 for RECIST 1.1, 0.716 for PERCIST 1.0, and 0.739 for EAU/EANM recommended criteria. Multivariate logistic analysis revealed that the post-NCHT maximum standardized uptake value (SUVmax) before radical prostatectomy was an independent predictor of a favourable pathological response to NCHT.

CONCLUSIONS

[⁶⁸Ga]Ga-PSMA-11 PET/CT had a better concordance with a favourable pathological response to NCHT compared with nadir PSA and mpMRI. EAU/EANM recommended criteria and PERCIST 1.0 criteria performed equally to identify pathological responders when [⁶⁸Ga]Ga-PSMA-11 PET/CT was used as a therapeutic response assessment tool.

Development and validation of a nomogram for predicting the likelihood of metastasis in prostate cancer patients undergoing Ga-68 PSMA PET/CT due to biochemical recurrence

OBJECTIVE

To develop a nomogram based on commonly used clinical data for predicting the likelihood of metastasis in gallium-68 prostate-specific membrane antigen PET/computed tomography (Ga-68 PSMA PET/CT) scans of prostate cancer patients with confirmed biochemical recurrence (BCR).

METHODS

One-hundred thirty-five ( n  = 135) patients who underwent Ga-68 PSMA PET/CT due to BCR were included in the study. Predictors of metastasis in Ga-68 PSMA PET/CT were determined with multivariable logistic regression analysis. Coefficients derived from the regression model were used to develop a prediction nomogram. The performance of the prediction model was evaluated with receiver operating characteristic analysis. Internal validation was performed with 50 bootstrap resamples, and the nomogram's clinical benefit was assessed with decision curve analysis.

RESULTS

Multivariable logistic regression analysis revealed that ISUP group, prostate-specific antigen (PSA) before PET and PSA doubling time were independent predictors of metastasis in Ga-68 PSMA PET/CT. A prediction nomogram was developed according to this model [the area under curve: 0.866; 95% confidence interval (CI), 0.788-0.944]. The best cutoff value of the nomogram-derived likelihood for predicting metastasis was 60%, with a bootstrap-corrected accuracy of 78.8%. An online version of the nomogram was implemented on pro-gram.nzm.co ( https://pro-gram.nzm.co ).

CONCLUSION

The proposed nomogram provides a practical approach for predicting the likelihood of imaging-based metastasis according to Ga-68 PSMA PET/CT in patients with BCR, with results ≥60% being the most accurate cutoff for referring patients to Ga-68 PSMA PET/CT. If validated in a larger cohort, this tool can serve as a guide for the appropriate use of Ga-68 PSMA PET/CT.

The role of Ga68 PSMA PET/CT imaging in Lu177 PSMA treatment planning in metastatic castration-resistant prostate cancer

OBJECTIVE

Lutetium-177 (Lu¹⁷⁷) prostate-specific membrane antigen (Lu¹⁷⁷ PSMA) is a novel targeted treatment for patients with metastatic castration-resistant prostate cancer (CRPC). The purpose of the study was to determine the molecular volumetric Gallium-68 (Ga⁶⁸) PSMA PET/CT parameters that can predict patients who will respond to treatment.

METHODS

These single-center retrospective data were obtained from metastatic CRPC patients receiving intravenous 6.0-8.5 GBq Lu¹⁷⁷ PSMA treatment every 6-8 weeks for a maximum of 3-8 cycles, with baseline Ga⁶⁸ PSMA PET/CT scan, clinical data, and information on treatment responses. All lesions were divided into two groups according to the increase and decrease in PSMA expression levels of 600 bone lesions and 85 lymph nodes that were compatible with metastasis of 23 patients after the treatment. The primary endpoint of our study was the evaluation of the relation between the baseline SUVmax, PSMA TV, TL PSMA values, and the treatment response of the two groups. The threshold values were determined for the parameters that had significant relations. In the present study, the prostate-specific antigen (PSA) response and treatment-induced toxicities were also evaluated as the secondary endpoint.

RESULTS

It was found that SUVmax, PSMA TV, and TL PSMA values in bone metastases showed significant differences between the groups with decreased and increased PSMA expression levels after the treatment. The AUC value for SUVmax was significant (AUC = 0.677; p < 0.001). The cutoff value was > 10.50 (sensitivity = 91.8%, Specificity = 41.5%) for SUVmax, > 1.50 cm³ (sensitivity = 49.1%, specificity = 70%) for PSMA TV and > 8.50 g (sensitivity = %60.9, specificity = %72.2) for TL PSMA. The median SUVmax value before the treatment in all metastatic lymph nodes was found to be 7.1 (5.4-12.4), and the median SUVmax after the treatment was 2.5 (1.6-12.1) (p < 0.001).

CONCLUSION

It was shown in the present study that Lu¹⁷⁷ PSMA treatment response may be higher in CRPC patients with metastatic bone lesion with high baseline PSMA expression level, and better treatment response may be achieved in patients with lymph node metastases than in bone metastases.

Bone Metastases Are Measurable: The Role of Whole-Body MRI and Positron Emission Tomography

Metastatic tumor deposits in bone marrow elicit differential bone responses that vary with the type of malignancy. This results in either sclerotic, lytic, or mixed bone lesions, which can change in morphology due to treatment effects and/or secondary bone remodeling. Hence, morphological imaging is regarded unsuitable for response assessment of bone metastases and in the current Response Evaluation Criteria In Solid Tumors 1.1 (RECIST1.1) guideline bone metastases are deemed unmeasurable. Nevertheless, the advent of functional and molecular imaging modalities such as whole-body magnetic resonance imaging (WB-MRI) and positron emission tomography (PET) has improved the ability for follow-up of bone metastases, regardless of their morphology. Both these modalities not only have improved sensitivity for visual detection of bone lesions, but also allow for objective measurements of bone lesion characteristics. WB-MRI provides a global assessment of skeletal metastases and for a one-step "all-organ" approach of metastatic disease. Novel MRI techniques include diffusion-weighted imaging (DWI) targeting highly cellular lesions, dynamic contrast-enhanced MRI (DCE-MRI) for quantitative assessment of bone lesion vascularization, and multiparametric MRI (mpMRI) combining anatomical and functional sequences. Recommendations for a homogenization of MRI image acquisitions and generalizable response criteria have been developed. For PET, many metabolic and molecular radiotracers are available, some targeting tumor characteristics not confined to cancer type (e.g. 18F-FDG) while other targeted radiotracers target specific molecular characteristics, such as prostate specific membrane antigen (PSMA) ligands for prostate cancer. Supporting data on quantitative PET analysis regarding repeatability, reproducibility, and harmonization of PET/CT system performance is available. Bone metastases detected on PET and MRI can be quantitatively assessed using validated methodologies, both on a whole-body and individual lesion basis. Both have the advantage of covering not only bone lesions but visceral and nodal lesions as well. Hybrid imaging, combining PET with MRI, may provide complementary parameters on the morphologic, functional, metabolic and molecular level of bone metastases in one examination. For clinical implementation of measuring bone metastases in response assessment using WB-MRI and PET, current RECIST1.1 guidelines need to be adapted. This review summarizes available data and insights into imaging of bone metastases using MRI and PET.