Dual-Tracer PET-MRI-Derived Imaging Biomarkers for Prediction of Clinically Significant Prostate Cancer.

PURPOSE: To investigate if imaging biomarkers derived from 3-Tesla dual-tracer [(18)F]fluoromethylcholine (FMC) and [68Ga]Ga-PSMAHBED-CC conjugate 11 (PSMA)-positron emission tomography can adequately predict clinically significant prostate cancer (csPC). METHODS: We assessed 77 biopsy-proven PC patients who underwent 3T dual-tracer PET/mpMRI followed by radical prostatectomy (RP) between 2014 and 2017. We performed a retrospective lesion-based analysis of all cancer foci and compared it to whole-mount histopathology of the RP specimen. The primary aim was to investigate the pretherapeutic role of the imaging biomarkers FMC- and PSMA-maximum standardized uptake values (SUVmax) for the prediction of csPC and to compare it to the mpMRI-methods and PI-RADS score. RESULTS: Overall, we identified 104 cancer foci, 69 were clinically significant (66.3%) and 35 were clinically insignificant (33.7%). We found that the combined FMC+PSMA SUVmax were the only significant parameters (p < 0.001 and p = 0.049) for the prediction of csPC. ROC analysis showed an AUC for the prediction of csPC of 0.695 for PI-RADS scoring (95% CI 0.591 to 0.786), 0.792 for FMC SUVmax (95% CI 0.696 to 0.869), 0.852 for FMC+PSMA SUVmax (95% CI 0.764 to 0.917), and 0.852 for the multivariable CHAID model (95% CI 0.763 to 0.916). Comparing the AUCs, we found that FMC+PSMA SUVmax and the multivariable model were significantly more accurate for the prediction of csPC compared to PI-RADS scoring (p = 0.0123, p = 0.0253, respectively). CONCLUSIONS: Combined FMC+PSMA SUVmax seems to be a reliable parameter for the prediction of csPC and might overcome the limitations of PI-RADS scoring. Further prospective studies are necessary to confirm these promising preliminary results.

Differential impact of radiation therapy after radical prostatectomy on recurrence patterns: an assessment using [68Ga]Ga-PSMA ligand PET/CT(MRI).

PURPOSE: To evaluate the differential impact of postoperative radiotherapy (RT) on recurrence patterns in patients treated with radical prostatectomy (RP) using [68Ga]Ga-PSMAHBED-CC conjugate 11 positron emission tomography (PSMA 11-PET). METHODS: We assessed 162 consecutive patients who experienced biochemical recurrence (BCR) after RP for nonmetastatic prostate cancer (PC). All had at least one positive lesion on imaging. No patient was on androgen deprivation therapy (ADT). Patients were categorized into those who had received adjuvant/salvage RT ± ADT and those who did not (RP only). Lesion- and patient-based analyses were performed. The impact of the radiation field was assessed. RESULTS: Overall, 57 BCR patients underwent RP only, 105 received postoperative RT. Median PSA was 1.01 ng/ml (IQR 0.58-2). In the lesion-based analysis, compared to the RP only patients, those who had received postoperative RT, had less lymph node (LN) recurrences distal to the common iliac bifurcation (35.2 vs. 57.9%, p = 0.05), but were more likely to harbor positive LNs proximal to the iliac bifurcation and in the presacral (34.2 vs. 12.3%, p = 0.002) areas as well as bone metastases (25.7 vs. 8.8%, p = 0.01). In the patient-based analysis, the patients with postoperative RT after RP had less recurrence in the pelvis only (pelvic LNs and/or prostate bed) (52.4 vs. 79%, p = 0.002), but were more likely to harbor extrapelvic recurrence (41.9 vs. 15.8%, p = 0.001). Patients who received RT to the prostate bed only had more recurrence to the pelvic LN only (54.2% vs. 23.4%, p = 0.002), but less extrapelvic recurrence (31.3 vs. 53.2%, p = 0.03) and less bone recurrence (16.7 vs. 36.2%, p = 0.031) compared to those patients, who received RT to the prostate bed and pelvic nodes. CONCLUSIONS: Postoperative radiation treatment alters the recurrence pattern in BCR patients after RP. Further prospective studies are needed to establish a decision tree for optimal imaging/management according to previous treatments.

Response assessment using [68 Ga]Ga-PSMA ligand PET in patients undergoing systemic therapy for metastatic castration-resistant prostate cancer.

BACKGROUND: To assess which parameters of [68 Ga]Ga-PSMA-11 positron emission tomography (PSMA-PET) predict response to systemic therapies in metastatic (m) castration-resistant prostate cancer (CRPC). In addition, to investigate which of these factors are associated with overall survival (OS). METHODS: We retrospectively assessed the following PSMA-PET parameters in 43 patients before and after systemic therapies for mCRPC: PSMA total tumor volume (TTV), mean standardized uptake value (SUVmean), SUVmax, and SUVpeak. prostate-specific antigen (PSA) levels and PSMA-PET/CT(magnetic resonance imaging [MRI]) imaging were both performed within 8 weeks before and 6 weeks after systemic therapy. PSMA-PET and CT (MRI) images were reviewed according to the modified PET Response Criteria in Solid Tumors (PERCIST) and Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Results were compared to PSA response. Univariable survival analyses were performed. RESULTS: Overall, 43 patients undergoing 67 systemic therapies were included (9 patients radium-223, 12 cabazitaxel, 22 docetaxel, 6 abiraterone, and 18 enzalutamide). Median serum PSA level before any therapy was 11.3 ng/mL (interquartile range [IQR] = 3.3, 30.1). Delta (d) PSA after systemic therapies was -41%, dTTV 10.5%, dSUVmean -7.5%, dSUVmax -13.3%, dSUVpeak -12%, and dRECIST -13.3%. Overall, 31 patients had dPSA response (46.3%), 12 stable disease (17.9%), and 24 progressive disease (35.8%). All observed PET parameters, as well as the RECIST evaluation, were significantly associated with PSA response (dTTV P = .003, dSUVmean P = .003, dSUVmax P = .011, dSUVpeak P < 0001, dRECIST P = .012), while RECIST assessment was applicable in 37 out of 67 patients (55.2%). Within a median follow-up of 33 months (IQR = 26, 38), 10 patients (23.3%) died of PC. On univariable survival analyses, neither the investigated PET parameters nor PSA level or RECIST criteria were associated with OS. CONCLUSION: PSMA-PET provides reliable parameters for prediction of response to systemic therapies for mCRPC. These parameters, if confirmed, could enhance RECIST criteria, specifically concerning its limitations for sclerotic bone lesions.

Response assessment using 68Ga-PSMA ligand PET in patients undergoing 177Lu-PSMA radioligand therapy for metastatic castration-resistant prostate cancer.

PURPOSE: The first aim of this study was to evaluate 68Ga-PSMAHBED-CC conjugate 11 positron emission tomography (PSMA PET) parameters for assessment of response to 177Lu-PSMA-617 radioligand therapy (RLT) in patients with metastatic castration-resistant prostate cancer (mCRPC). The second aim was to investigate factors associated with overall survival (OS). METHODS: We retrospectively assessed mean standardized uptake values (SUVmean) and total tumor volumes (TTV) on PSMA PET in 38 of 55 mCRPC patients before and after RLT. PSA testing and PSMA PET/CT(MRI) imaging were performed during the 8 weeks before and the 6 weeks after RLT. PSMA PET and CT(MRI) images were reviewed separately according to the modified PET Response Criteria in Solid Tumors (mPERCIST) and RECIST1.1. The results were compared with PSA responses. Associations between OS and the RECIST evaluation and changes in SUVmean, TTV, and PSA, CRP, LDH, hemoglobin and ALP levels were determined in a univariable survival analysis. RESULTS: The median PSA level at the time of pretherapy PSMA PET/CT(MRI) was 60.8 ng/ml (IQR 15.4, 264.2 ng/ml). After RLT the median PSA level decreased by 44%, TTV by 45.1%, SUVmean by 25.8% and RECIST by 11.3%. A PSA response was seen in 18 patients (47.4%), stable disease in 12 (31.6%) and progressive disease in 8 (21.1%). Contrary to the changes in SUVmean and the RECIST evaluation, the change in TTV was significantly associated with PSA response (p = 0.15, p = 0.58, and p < 0.001, respectively). After a median follow-up of 17 months (IQR 8.0, 24.2 months), 11 patients (28.9%) had died of their prostate cancer. The changes in both TTV and PSA levels were associated with OS (HR 1.001, 95% CI 1-1.003, p = 0.04, and HR 1.004, 95% CI 1.001-1.008, p = 0.01, respectively), while the changes in SUVmean and the RECIST evaluation were not. The pre-therapy CRP level was also associated with OS (HR 1.07, 95% CI 1.009-1.14, p = 0.02). CONCLUSION: TTV on PSMA PET seems to be a reliable parameter for response assessment in mCRPC patients undergoing RLT and might overcome the limitations of RECIST in prostate cancer. Furthermore, the change in TTV was significantly associated with OS in our cohort.