Long-term outcome of biologically guided dose-escalated radiotherapy of localized prostate cancer.

BACKGROUND: Biologically created subvolumes enable non-uniform dose distributions in prostate cancer radiotherapy (RT) thus potentially improving therapeutic ratio and reducing toxicity. We present the long-term outcome of men receiving focal boosting of carbon-11 acetate (ACE) PET-CT metabolically active areas in prostate carcinoma. MATERIAL AND METHODS: Thirty men with hormone naïve localized prostate carcinoma underwent ACE PET/CT for RT planning. There were five low-, 17 intermediate-, and eight high-risk patients. Based on thresholding of the standardized uptake values (SUVs) metabolic target volumes (MTVs) corresponding to intraprostatic lesions (IPLs) were contoured. Two planning target volumes (PTVs) were applied i.e., PTVlow-risk for the whole prostate with 8-10 mm margin and PTVhigh-risk for the MTV. Pelvic nodes were not irradiated. Late toxicity of biologically guided RT was reviewed after a median of 63 months and outcome after a median follow-up of 124 months. RESULTS: Median doses to PTVlow-risk, PTVhigh-risk, prostate, and MTV were 72.9 Gy, 79.4 Gy, 76.6 Gy, and 80.4 Gy, respectively, in 38 fractions. The 10-year cancer-specific survival was 86% and the biochemical failure-free ratio 68%, respectively. The median biochemical progression-free survival (PFS) was 37, 108, and 119 months in the high, intermediate, and low-risk groups, respectively, the difference being significant between high and intermediate-risk groups (p = 0.02). One patient (3%) presented with locoregional and 5 (17%) with distant nodal metastases. Five patients (17%) had a biochemical relapse. A larger MTV was associated with shorter PFS (r = -0.41, p = 0.02), but had no influence on OS. No other statistically significant differences in the dose painting parameters were observed between recurrence-free and recurring patients. CONCLUSIONS: Biological guidance for dose-escalated prostate RT is feasible with ACE PET/CT. Since a larger MTV may be associated with a higher risk for progression, we encourage further study of dose-escalation to ACE-positive lesions considering the low toxicity of our protocol.

Kinetic analysis and optimisation of 18F-rhPSMA-7.3 PET imaging of prostate cancer.

PURPOSE: This phase 1 open-label study evaluated the uptake kinetics of a novel theranostic PET radiopharmaceutical, 18F-rhPSMA-7.3, to optimise its use for imaging of prostate cancer. METHODS: Nine men, three with high-risk localised prostate cancer, three with treatment-naïve hormone-sensitive metastatic disease and three with castration-resistant metastatic disease, underwent dynamic 45-min PET scanning of a target area immediately post-injection of 300 MBq 18F-rhPSMA-7.3, followed by two whole-body PET/CT scans acquired from 60 and 90 min post-injection. Volumes of interest (VoIs) corresponding to prostate cancer lesions and reference tissues were recorded. Standardised uptake values (SUV) and lesion-to-reference ratios were calculated for 3 time frames: 35-45, 60-88 and 90-118 min. Net influx rates (Ki) were calculated using Patlak plots. RESULTS: Altogether, 44 lesions from the target area were identified. Optimal visual lesion detection started 60 min post-injection. The 18F-rhPSMA-7.3 signal from prostate cancer lesions increased over time, while reference tissue signals remained stable or decreased. The mean (SD) SUV (g/mL) at the 3 time frames were 8.4 (5.6), 10.1 (7) and 10.6 (7.5), respectively, for prostate lesions, 11.2 (4.3), 13 (4.8) and 14 (5.2) for lymph node metastases, and 4.6 (2.6), 5.7 (3.1) and 6.4 (3.5) for bone metastases. The mean (SD) lesion-to-reference ratio increases from the earliest to the 2 later time frames were 40% (10) and 59% (9), respectively, for the prostate, 65% (27) and 125% (47) for metastatic lymph nodes and 25% (19) and 32% (30) for bone lesions. Patlak plots from lesion VoIs signified almost irreversible uptake kinetics. Ki, SUV and lesion-to-reference ratio estimates showed good agreement. CONCLUSION: 18F-rhPSMA-7.3 uptake in prostate cancer lesions was high. Lesion-to-background ratios increased over time, with optimal visual detection starting from 60 min post-injection. Thus, 18F-rhPSMA-7.3 emerges as a very promising PET radiopharmaceutical for diagnostic imaging of prostate cancer. TRIAL REGISTRATION: NCT03995888 (24 June 2019).

Prospective evaluation of 18F-FACBC PET/CT and PET/MRI versus multiparametric MRI in intermediate- to high-risk prostate cancer patients (FLUCIPRO trial).

PURPOSE: The purpose of this study was to evaluate 18F-FACBC PET/CT, PET/MRI, and multiparametric MRI (mpMRI) in detection of primary prostate cancer (PCa). METHODS: Twenty-six men with histologically confirmed PCa underwent PET/CT immediately after injection of 369 ± 10 MBq 18F-FACBC (fluciclovine) followed by PET/MRI started 55 ± 7 min from injection. Maximum standardized uptake values (SUVmax) were measured for both hybrid PET acquisitions. A separate mpMRI was acquired within a week of the PET scans. Logan plots were used to calculate volume of distribution (VT). The presence of PCa was estimated in 12 regions with radical prostatectomy findings as ground truth. For each imaging modality, area under the curve (AUC) for detection of PCa was determined to predict diagnostic performance. The clinical trial registration number is NCT02002455. RESULTS: In the visual analysis, 164/312 (53%) regions contained PCa, and 41 tumor foci were identified. PET/CT demonstrated the highest sensitivity at 87% while its specificity was low at 56%. The AUC of both PET/MRI and mpMRI significantly (p < 0.01) outperformed that of PET/CT while no differences were detected between PET/MRI and mpMRI. SUVmax and VT of Gleason score (GS) >3 + 4 tumors were significantly (p < 0.05) higher than those for GS 3 + 3 and benign hyperplasia. A total of 442 lymph nodes were evaluable for staging, and PET/CT and PET/MRI demonstrated true-positive findings in only 1/7 patients with metastatic lymph nodes. CONCLUSIONS: Quantitative 18F-FACBC imaging significantly correlated with GS but failed to outperform MRI in lesion detection. 18F-FACBC may assist in targeted biopsies in the setting of hybrid imaging with MRI.

Prospective evaluation of planar bone scintigraphy, SPECT, SPECT/CT, 18F-NaF PET/CT and whole body 1.5T MRI, including DWI, for the detection of bone metastases in high risk breast and prostate cancer patients: SKELETA clinical trial.

PURPOSE: Detection of bone metastases in breast and prostate cancer patients remains a major clinical challenge. The aim of the current trial was to compare the diagnostic accuracy of (99m)Tc-hydroxymethane diphosphonate ((99m)Tc-HDP) planar bone scintigraphy (BS), (99m)Tc-HDP SPECT, (99m)Tc-HDP SPECT/CT, (18)F-NaF PET/CT and whole body 1.5 Tesla magnetic resonance imaging (MRI), including diffusion weighted imaging, (wbMRI+DWI) for the detection of bone metastases in high risk breast and prostate cancer patients. MATERIAL AND METHODS: Twenty-six breast and 27 prostate cancer patients at high risk of bone metastases underwent (99m)Tc-HDP BS, (99m)Tc-HDP SPECT, (99m)Tc-HDP SPECT/CT, (18)F-NaF PET/CT and wbMRI+DWI. Five independent reviewers interpreted each individual modality without the knowledge of other imaging findings. The final metastatic status was based on the consensus reading, clinical and imaging follow-up (minimal and maximal follow-up time was 6, and 32 months, respectively). The bone findings were compared on patient-, region-, and lesion-level. RESULTS: (99m)Tc-HDP BS was false negative in four patients. In the region-based analysis, sensitivity values for (99m)Tc-HDP BS, (99m)Tc-HDP SPECT, (99m)Tc-HDP SPECT/CT, (18)F-NaF PET/CT, and wbMRI+DWI were 62%, 74%, 85%, 93%, and 91%, respectively. The number of equivocal findings for (99m)Tc-HDP BS, (99m)Tc-HDP SPECT, (99m)Tc-HDP SPECT/CT, (18)F-NaF PET/CT and wbMRI+DWI was 50, 44, 5, 6, and 4, respectively. CONCLUSION: wbMRI+DWI showed similar diagnostic accuracy to (18)F-NaF PET/CT and outperformed (99m)Tc-HDP SPECT/CT, and (99m)Tc-HDP BS.

Uptake of 18F-rhPSMA-7.3 in Positron Emission Tomography Imaging of Prostate Cancer: A Phase 1 Proof-of-Concept Study.

Background: This study evaluated tracer uptake and lesion detectability with the novel radiopharmaceutical 18F-radiohybrid (rh)PSMA-7.3 in patients with prostate cancer (PCa). Materials and Methods: Ten patients (three with high-risk primary localized PCa [Cohort A], three with hormone-sensitive metastatic PCa [Cohort B], and four with castration-resistant metastatic PCa [Cohort C]) underwent whole-body 18F-rhPSMA-7.3 positron emission tomography (PET)/computed tomography (CT) and findings were correlated with standard-of-care imaging. 18F-rhPSMA-7.3 maximum standardized uptake value (SUVmax) and its possible association with Gleason score (GS)/International Society of Urological Pathology (ISUP) grade group (GG) and serum PSA levels were evaluated. Cohort A 18F-rhPSMA-7.3 findings were also correlated with histopathology, including prostate-specific membrane antigen (PSMA) staining. Results: 18F-rhPSMA-7.3 identified the primary tumor in 3/3 Cohort A patients and lymph node (LN) and/or bone lesions in 7/7 metastatic patients. All prostate lesions with GS ≥4 + 3/GG ≥3 were identified, but only 1/4 GS ≤3 + 4/GG ≤2 lesions. Prostate lesion SUVmax appeared positively associated with GS/GGs. Among metastatic patients, 18F-rhPSMA-7.3 identified all known pelvic and extrapelvic LN metastases and all known bone lesions. 18F-rhPSMA-7.3 detected possible additional nodal and bone lesions not reported in standard-of-care imaging in all metastatic patients. No association existed between bone or LN uptake and either GS/GG or PSA. Conclusions: 18F-rhPSMA-7.3 PET/CT showed good detection of primary and metastatic PCa lesions. In this small patient population, 18F-rhPSMA-7.3 identified intraprostatic lesions with GS ≥4 + 3/GG ≥3 with good accuracy.

Comparison of reprojected bone SPECT/CT and planar bone scintigraphy for the detection of bone metastases in breast and prostate cancer.

OBJECTIVE: The aim of this study was to compare reprojected bone SPECT/CT (RBS) against planar bone scintigraphy (BS) in the detection of bone metastases in breast and prostate cancer patients. METHODS: Twenty-six breast and 105 prostate cancer patients with high risk for bone metastases underwent 99mTc-HMDP BS and whole-body SPECT/CT, 1.5-T whole-body diffusion-weighted MRI and 18F-NaF or 18F-PSMA-1007 PET/CT within two prospective clinical trials (NCT01339780 and NCT03537391). Consensus reading of all imaging modalities and follow-up data were used to define the reference standard diagnosis. The SPECT/CT data were reprojected into anterior and posterior views to produce RBS images. Both BS and RBS images were independently double read by two pairs of experienced nuclear medicine physicians. The findings were validated against the reference standard diagnosis and compared between BS and RBS on the patient, region and lesion levels. RESULTS: All metastatic patients detected by BS were also detected by RBS. In addition, three metastatic patients were missed by BS but detected by RBS. The average patient-level sensitivity of two readers for metastases was 75% for BS and 87% for RBS, and the corresponding specificity was 79% for BS and 39% for RBS. The average region-level sensitivity of two readers was 64% for BS and 69% for RBS, and the corresponding specificity was 96% for BS and 87% for RBS. CONCLUSION: Whole-body bone SPECT/CT can be reprojected into more familiar anterior and posterior planar images with excellent sensitivity for bone metastases, making additional acquisition of planar BS unnecessary.

Safety, Biodistribution, and Radiation Dosimetry of 18F-rhPSMA-7.3 in Healthy Adult Volunteers.

This first-in-humans study investigated the safety, biodistribution, and radiation dosimetry of a novel 18F-labeled radiohybrid prostate-specific membrane antigen (rhPSMA) PET imaging agent, 18F-rhPSMA-7.3. Methods: Six healthy volunteers (3 men, 3 women) underwent multiple whole-body PET acquisitions at scheduled time points up to 248 min after the administration of 18F-rhPSMA-7.3 (mean activity, 220; range, 210-228 MBq). PET scans were conducted in 3 separate sessions, and subjects were encouraged to void between sessions. Blood and urine samples were collected for up to 4 h after injection to assess metabolite-corrected radioactivity in whole blood, plasma, and urine. Quantitative measurements of 18F radioactivity in volumes of interest over target organs were determined directly from the PET images at 8 time points, and normalized time-activity concentration curves were generated. These normalized cumulated activities were then inputted into the OLINDA/EXM package to calculate the internal radiation dosimetry and the subjects' effective dose. Results:18F-rhPSMA-7.3 was well tolerated. One adverse event (mild headache, not requiring medication) was considered possibly related to 18F-rhPSMA-7.3. The calculated effective dose was 0.0141 mSv/MBq when using a 3.5-h voiding interval. The organs with the highest mean absorbed dose per unit of administered radioactivity were the adrenals (0.1835 mSv/MBq), the kidneys (0.1722 mSv/MBq), the submandibular glands (0.1479 mSv), and the parotid glands (0.1137 mSv/MBq). At the end of the first scanning session (mean time, 111 min after injection), an average of 7.2% (range, 4.4%-9.0%) of the injected radioactivity of 18F-rhPSMA-7.3 was excreted into urine. Conclusion: The safety, biodistribution, and internal radiation dosimetry of 18F-rhPSMA-7.3 are considered favorable for PET imaging.

Validation of automated magnetic resonance image segmentation for radiation therapy planning in prostate cancer.

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) is increasingly used in radiation therapy planning of prostate cancer (PC) to reduce target volume delineation uncertainty. This study aimed to assess and validate the performance of a fully automated segmentation tool (AST) in MRI based radiation therapy planning of PC. MATERIAL AND METHODS: Pelvic structures of 65 PC patients delineated in an MRI-only workflow according to established guidelines were included in the analysis. Automatic vs manual segmentation by an experienced oncologist was compared with geometrical parameters, such as the dice similarity coefficient (DSC). Fifteen patients had a second MRI within 15 days to assess repeatability of the AST for prostate and seminal vesicles. Furthermore, we investigated whether hormonal therapy or body mass index (BMI) affected the AST results. RESULTS: The AST showed high agreement with manual segmentation expressed as DSC (mean, SD) for delineating prostate (0.84, 0.04), bladder (0.92, 0.04) and rectum (0.86, 0.04). For seminal vesicles (0.56, 0.17) and penile bulb (0.69, 0.12) the respective agreement was moderate. Performance of AST was not influenced by neoadjuvant hormonal therapy, although those on treatment had significantly smaller prostates than the hormone-naïve patients (p < 0.0001). In repeat assessment, consistency of prostate delineation resulted in mean DSC of 0.89, (SD 0.03) between the paired MRI scans for AST, while mean DSC of manual delineation was 0.82, (SD 0.05). CONCLUSION: Fully automated MRI segmentation tool showed good agreement and repeatability compared with manual segmentation and was found clinically robust in patients with PC. However, manual review and adjustment of some structures in individual cases remain important in clinical use.

Prediction of prostate cancer aggressiveness using 18F-Fluciclovine (FACBC) PET and multisequence multiparametric MRI.

The aim of this prospective single-institution clinical trial (NCT02002455) was to evaluate the potential of advanced post-processing methods for 18F-Fluciclovine PET and multisequence multiparametric MRI in the prediction of prostate cancer (PCa) aggressiveness, defined by Gleason Grade Group (GGG). 21 patients with PCa underwent PET/CT, PET/MRI and MRI before prostatectomy. DWI was post-processed using kurtosis (ADCk, K), mono- (ADCm), and biexponential functions (f, Dp, Df) while Logan plots were used to calculate volume of distribution (VT). In total, 16 unique PET (VT, SUV) and MRI derived quantitative parameters were evaluated. Univariate and multivariate analysis were carried out to estimate the potential of the quantitative parameters and their combinations to predict GGG 1 vs >1, using logistic regression with a nested leave-pair out cross validation (LPOCV) scheme and recursive feature elimination technique applied for feature selection. The second order rotating frame imaging (RAFF), monoexponential and kurtosis derived parameters had LPOCV AUC in the range of 0.72 to 0.92 while the corresponding value for VT was 0.85. The best performance for GGG prediction was achieved by K parameter of kurtosis function followed by quantitative parameters based on DWI, RAFF and 18F-FACBC PET. No major improvement was achieved using parameter combinations with or without feature selection. Addition of 18F-FACBC PET derived parameters (VT, SUV) to DWI and RAFF derived parameters did not improve LPOCV AUC.

Comparison of standardized uptake values between 99mTc-HDP SPECT/CT and 18F-NaF PET/CT in bone metastases of breast and prostate cancer.

BACKGROUND: Despite recent technological advances allowing for quantitative single-photon emission computed tomography (SPECT), quantitative SPECT has not been widely used in the clinical practice. The aim of this study is to evaluate the feasibility of quantitative SPECT for measuring metastatic bone uptake in breast and prostate cancer by comparing standard uptake values (SUVs) measured with 99mTc-HDP SPECT/CT and 18F-NaF PET/CT. METHODS: Twenty-six breast and 27 prostate cancer patients at high risk of bone metastases underwent both 99mTc-HDP SPECT/CT and 18F-NaF PET/CT within 14 days of each other. The SPECT and PET data were reconstructed using ordered-subset expectation-maximization algorithms achieving quantitative images. Metastatic and benign skeletal lesions visible in both data sets were identified, and their maximum, peak, and mean SUVs (SUVmax, SUVpeak, and SUVmean) were determined. SUV ratios (SUVRs) between the lesions and adjacent normal appearing bone were also calculated. Linear regression was used to evaluate the correlations between the SUVs of SPECT and PET and Bland-Altman plots to evaluate the differences between the SUVs and SUVRs of SPECT and PET. RESULTS: A total of 231 skeletal lesions, 129 metastatic and 102 benign, were analyzed. All three SUV measures correlated very strongly between SPECT and PET (R2 ≥ 0.80, p < 0.001) when all lesions were included, and the PET SUVs were significantly higher than SPECT SUVs (p < 0.001). The median differences were 21%, 12%, and 19% for SUVmax, SUVpeak, and SUVmean, respectively. On the other hand, the SUVRs were similar between SPECT and PET with median differences of 2%, - 9%, and 2% for SUVRmax, SUVRpeak, and SUVRmean, respectively. CONCLUSION: The strong correlation between SUVs and similar SUVRs of 99mTc-HDP SPECT/CT and 18F-NaF PET/CT demonstrate that SPECT is an applicable tool for clinical quantification of bone metabolism in osseous metastases in breast and prostate cancer patients.

Correlation between 18F-1-amino-3-fluorocyclobutane-1-carboxylic acid (18F-fluciclovine) uptake and expression of alanine-serine-cysteine-transporter 2 (ASCT2) and L-type amino acid transporter 1 (LAT1) in primary prostate cancer.

PURPOSE: To evaluate the expression of alanine-serine-cysteine-transporter 2 (ASCT2) and L-type amino acid transporter1 (LAT1) in prostate cancer (PCa) and their impact on uptake of 18F-1-amino-3-fluorocyclobutane-1-carboxylic acid (18F-fluciclovine) which is approved for the detection of recurrent PCa. METHODS: Twenty-five hormone-naïve patients with histologically confirmed PCa underwent PET/CT before prostatectomy. Dynamic imaging was performed immediately after injection of 368 ± 10 MBq of 18F-fluciclovine and the uptake in PCa was expressed as SUVmax at six sequential 4-min time frames and as tracer distribution volume (VT) using Logan plots over 0-24 min. The expression of ASCT2 and LAT1 was studied with immunohistochemistry (IHC) on a tissue microarray (TMA) containing three cores per carcinoma lesion. The TMA slides were scored independently by two trained readers based on visual intensity of ASCT2/LAT1 expression on a four-tiered scale. The correlations between ASCT2/LAT1 staining intensity, SUVmax/VT, and Gleason grade group (GGG) were assessed using Spearman's rank correlation coefficient (ρ). RESULTS: Forty tumor foci (> 0.5 mm in diameter, max. 3 per patient) were available for TMA. In visual scoring, low, moderate, and high staining intensity of ASCT2 was observed in 4 (10%), 24 (60%), and 12 (30%) tumors, respectively. No tumors showed high LAT1 staining intensity while moderate intensity was found in 10 (25%), 25 (63%) showed low, and the remaining 5 (12%) were negative for staining with LAT1. Tumors with GGG > 2 showed significantly higher uptake of 18F-fluciclovine and higher LAT1 staining intensity (p < 0.05). The uptake of 18F-fluciclovine correlated significantly with LAT1 expression (ρ = 0.39, p = 0.01, for SUVmax at 2 min and ρ = 0.39, p = 0.01 for VT). No correlation between ASCT2 expression and 18F-fluciclovine uptake or GGG was found. CONCLUSIONS: Our findings suggest that LAT1 is moderately associated with the transport of 18F-fluciclovine in local PCa not exposed to hormonal therapy. Both high and low Gleason grade tumors express ASCT2 while LAT1 expression is less conspicuous and may be absent in some low-grade tumors. Our observations may be of importance when using 18F-fluciclovine imaging in the planning of focal therapies for PCa.

In vivo imaging of prostate cancer using [68Ga]-labeled bombesin analog BAY86-7548.

PURPOSE: A novel [(68)Ga]-labeled DOTA-4-amino-1-carboxymethyl-piperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 peptide (BAY86-7548) having high affinity to bombesin receptor subtype II to detect primary and metastatic prostate carcinoma using positron emission tomography/computed tomography (PET/CT) was synthesized and evaluated for prostate cancer. EXPERIMENTAL DESIGN: In this first human study with BAY86-7548, 14 men scheduled for radical prostatectomy (n = 11) or with biochemical recurrence after surgery or hormonal therapy (n = 3) were enrolled. The patients received an intravenous injection of BAY86-7548 followed by over 60-minute dynamic imaging of prostate gland (n = 10) and/or subsequent whole-body imaging (n = 14). The visual assessment of PET/CT images included evaluation of intraprostatic (12 subsextants) and pelvic nodal uptake of BAY86-7548 in 11 surgical patients and detection of potential metastatic foci in all patients. In patients with biochemical recurrence, results were compared with those of either [(11)C]-acetate (n = 2) or [(18)F]-fluoromethylcholine (n = 1) PET/CT. RESULTS: We found a sensitivity, specificity, and accuracy of 88%, 81% and 83%, respectively, for detection of primary PCa and sensitivity of 70% for metastatic lymph nodes using histology as gold standard. BAY86-7548 correctly detected local recurrence in prostate bed and showed nodal relapse in accordance with [(11)C]-acetate PET/CT in 2 patients with biochemical relapse. In the third hormone refractory patient, BAY86-7548 failed to show multiple bone metastases evident on [(18)F]-fluoromethylcholine PET/CT. CONCLUSION: BAY86-7548 PET/CT is a promising molecular imaging technique for detecting intraprostatic prostate cancer.