Diagnostic performance of <Superscript>11</Superscript>C-choline PET/CT and FDG PET/CT for staging and restaging of renal cell cancer

Purpose

To compare findings obtained with ¹¹C-choline and FDG PET/CT scanning for renal cell carcinoma staging and restaging.

Materials and methods

Twenty-eight renal cell carcinoma patients whose histological subtype was clear cell type in 26 and papillary type in 2, while Fuhrman nuclear grade was G1,2 in 16 and G3,4 in 12, underwent both ¹¹C-choline and FDG PET/CT examinations before (n?=?10) and/or after (n?=?18) treatment, then those scanning modalities were compared in regard to patient- and lesion-based diagnostic performance using 5 grading scores. Final diagnosis in each case was obtained based on histopathology, conventional radiological imaging, and clinical follow-up findings. The differences between ¹¹C-choline and FDG PET/CT findings were evaluated using receiver-operating-characteristic (ROC) analysis and a McNemar test.

Results

Patient-based sensitivity, specificity, positive predictive, negative predictive, accuracy, and area under the ROC curve (AUC) values for ¹¹C-choline PET/CT for staging and restaging were 88.0% (22/25), 66.7% (2/3), 95.7% (22/23), 40.0% (2/5), 85.7% (24/28), and 0.887, respectively, while those for FDG-PET/CT were 56.0% (14/25), 66.7% (2/3), 93.3% (14/15), 15.4% (2/13), 57.1% (16/28), and 0.647, respectively. Sensitivity, accuracy, and AUC were significantly different (p?=?0.013, p?=?0.013, p?=?0.012, respectively). Among the 120 lesions, those with kidney, lung, lymph node, bone, pancreas, venous tumor thrombosis, adrenal gland, liver, or skin localization numbered 15, 64, 16, 13, 4, 3, 2, 2, and 1, respectively. For all 120 lesions, 75 (62.5%) and 47 (39.2%) were detected by ¹¹C-choline and FDG PET/CT, respectively (p?<?0.0001).

Conclusion

For staging and restaging of renal cell carcinoma patients, ¹¹C-choline-PET/CT is significantly more useful than FDG-PET/CT.

     

Prospective head-to-head comparison of <Superscript>11</Superscript>C-choline-PET/MR and <Superscript>11</Superscript>C-choline-PET/CT for restaging of biochemical recurrent prostate cancer

Purpose

Whole-body integrated ¹¹C-choline PET/MR might provide advantages compared to ¹¹C-choline PET/CT for restaging of prostate cancer (PC) due to the high soft-tissue contrast and the use of multiparametric MRI, especially for detection of local recurrence and bone metastases.

Materials and methods

Ninety-four patients with recurrent PC underwent a single-injection/dual-imaging protocol with contrast-enhanced PET/CT followed by fully diagnostic PET/MR. Imaging datasets were read separately by two reader teams (team 1 and 2) assessing the presence of local recurrence, lymph node and bone metastases in predefined regions using a five-point scale. Detection rates were calculated. The diagnostic performance of PET/CT vs. PET/MR was compared using ROC analysis. Inter-observer and inter-modality variability, radiation exposure, and mean imaging time were evaluated. Clinical follow-up, imaging, and/or histopathology served as standard of reference (SOR).

Results

Seventy-five patients qualified for the final image analysis. A total of 188 regions were regarded as positive: local recurrence in 37 patients, 87 regions with lymph node metastases, and 64 regions with bone metastases. Mean detection rate between both readers teams for PET/MR was 84.7% compared to 77.3% for PET/CT (p > 0.05). Local recurrence was identified significantly more often in PET/MR compared to PET/CT by team 1. Lymph node and bone metastases were identified significantly more often in PET/CT compared to PET/MR by both teams. However, this difference was not present in the subgroup of patients with PSA values ≤2 ng/ml.Inter-modality and inter-observer agreement (K > 0.6) was moderate to substantial for nearly all categories. Mean reduction of radiation exposure for PET/MR compared to PET/CT was 79.7% (range, 72.6–86.2%). Mean imaging time for PET/CT was substantially lower (18.4 ± 0.7 min) compared to PET/MR (50.4 ± 7.9 min).

Conclusions

¹¹C-choline PET/MR is a robust imaging modality for restaging biochemical recurrent PC and interpretations between different readers are consistent. It provides a higher diagnostic value for detecting local recurrence compared to PET/CT with the advantage of substantial dose reduction. Drawbacks of PET/MR are a substantially longer imaging time and a slight inferiority in detecting bone and lymph node metastases in patients with PSA values >2 ng/ml. Thus, we suggest the use of ¹¹C-choline PET/MR especially for patients with low (≤2 ng/ml) PSA values, whereas PET/CT is preferable in the subgroup with higher PSA values.

     

Evaluation of [<Superscript>18</Superscript>F]-choline PET/CT for staging and restaging of prostate cancer

Purpose To evaluate the accuracy of [¹⁸F]-choline (FCH) positron emission tomography/computed tomography (PET/CT) for staging and restaging of prostate cancer. Methods FCH PET/CT was performed in 111 patients with prostate cancer using 200 MBq FCH: 43 patients [mean age 63 years; mean prostrate specific antigen (PSA) 11.58 μg/l] were examined for initial staging, and 68 patients (mean age 66.4 years) were examined for restaging (mean PSA 10.81 μg/l). FCH PET/CT results were correlated to histopathology, bone scan, morphology as revealed by magnetic resonance imaging (MRI) and CT, PET/CT follow-up and PSA follow-up after therapy. Results FCH PET/CT scans at initial staging correctly showed no metastases in 36/38 patients undergoing radical surgery, as confirmed by PSA levels <0.1 μg/l 6 months postoperatively. Lymphadenectomy was performed in 24 of these patients, revealing four false FCH-negative lymph nodes (LN). In one patient, only lymphadenectomy was performed since a FCH-positive LN was confirmed by histology. Four patients showed FCH-positive bone metastases, as proven by bone scan. FCH PET/CT scans at restaging correctly revealed local recurrence in 36 patients. No pathological FCH uptake was observed in 11 patients with biochemical recurrence. Twenty-three patients showed FCH-positive LN. Twenty LN were surgically removed in seven patients. Histopathology verified metastases in all LN, but revealed two additional metastastic, FCH-negative LN. Seventeen patients showed FCH-positive bone metastases, as proven by bone scan or MRI. Sensitivity to detect recurrent disease was 86%. Conclusion The results obtained using FCH PET/CT scans for initial N-staging were discouraging, especially in terms of its inability to detect small metastases. Recurrent disease can be localized reliably in patients with PSA levels of >2 μg/l.     

Value of <Superscript>11</Superscript>C-choline PET and PET/CT in patients with suspected prostate cancer

Purpose: The value and limitations of ¹¹C-choline PET and PET/CT for the detection of prostate cancer remain controversial. The aim of this study was to investigate the diagnostic efficacy of ¹¹C-choline PET and PET/CT in a large group of patients with suspected prostate cancer. Methods: Fifty-eight patients with clinical suspicion of prostate cancer underwent ¹¹C-choline PET (25/58, Siemens ECAT Exact HR+) or PET/CT (33/58, Philips Gemini) scanning. On average, 500 MBq of ¹¹C-choline was administered intravenously. Studies were interpreted by raters blinded to clinical information and other diagnostic procedures. Qualitative image analysis as well as semiquantitative SUV measurement was carried out. The reference standard was histopathological examination of resection specimens or biopsy. Results: Prevalence of prostate cancer in this selected patient population was 63.8% (37/58). ¹¹C-choline PET and PET/CT showed a sensitivity of 86.5% (32/37) and a specificity of 61.9% (13/21) in the detection of the primary malignancy. With regard to metastatic spread, PET showed a per-patient sensitivity of 81.8% (9/11) and produced no false positive findings. Conclusion: Based on our findings, differentiation between benign prostatic changes, such as benign prostatic hyperplasia or prostatitis, and prostate cancer is feasible in the majority of cases when image interpretation is primarily based on qualitative characteristics. SUV_max may serve as guidance. False positive findings may occur due to an overlap of ¹¹C-choline uptake between benign and malignant processes. By providing functional information regarding both the primary malignancy and its metastases, ¹¹C-choline PET may prove to be a useful method for staging prostate cancer.     

Reproducibility of standardized uptake values of same-day randomized <Superscript>68</Superscript>Ga-PSMA-11 PET/CT and PET/MR scans in recurrent prostate cancer patients

Objective

Positron emission tomography in association with magnetic resonance imaging (PET/MR) and ⁶⁸Ga-PSMA-11 has shown superior detection in recurrent prostate cancer patients as compared to PET/computed tomography (PET/CT). There are, however, several technological differences between PET/CT and PET/MR systems which affect the PET image quality. The objective of this study was to assess the reproducibility of PET/CT and PET/MR SUV’s in recurrent prostate cancer patients. We randomized the patients regarding the order of the PET/CT and PET/MR scans to reduce the influence of tracer uptake as a function of time.

Methods

Thirty patients, all with biochemical recurrence after radical prostatectomy, underwent whole-body PET/CT and PET/MR scans after intravenous injection of a single dose of ⁶⁸Ga-PSMA-11. Fifteen patients underwent PET/CT first and 15 patients underwent PET/MR first. Volumes of interest on tumor lesions were outlined and maximum standardized uptake value (SUVmax) corrected for lean body mass was calculated. Correlation and agreement between scans were assessed by generalized linear mixed-effects models and Bland–Altman analysis. The association between SUV, patient characteristics and imaging parameters was assessed.

Results

Eighteen of the 30 evaluated patients had at least one positive lesion, giving an overall detection rate of 60%. In total, there were 34 visible lesions: 5 local recurrences, 22 lymph node metastases and 7 bone metastases. One group acquired PET/CT and PET/MR at median time points of 63.0 and 159.0 min, while the other group acquired PET/MR and PET/CT at median time points of 92.0 and 149.0 min. SUVmax between scans was linearly correlated, described by the equation Y(PET/CT SUVmax)?=?0.75?+?1.00?×?(PET/MR SUVmax), on average 20% higher on PET/CT than on PET/MR. SUV associated significantly only with type of lesion, scan time post-injection and acquisition time per bed position.

Conclusions

SUVmax from PET/CT and PET/MR are linearly correlated, on average 20% higher on PET/CT than on PET/MR and should, therefore, not be used interchangeably in patient follow-up.

     

<Superscript>68</Superscript>Ga-PSMA-11 dynamic PET/CT imaging in biochemical relapse of prostate cancer

Objectives

We aim to investigate the pharmacokinetics and distribution of the recently clinically introduced radioligand ⁶⁸Ga-PSMA-11 in men with recurrent prostate cancer (PC) by means of dynamic and whole-body PET/CT. The correlation between PSA levels and ⁶⁸Ga-PSMA-11 PET parameters is also investigated.

Methods

31 patients with biochemical failure after primary PC treatment with curative intent (median age 71.0 years) were enrolled in the analysis. The median PSA value was 2.0 ng/mL (range?=?0.1 – 130.0 ng/mL) and the median Gleason score was 7 (range?=?5 – 9). 8/31 (25.8 %) of the included patients had a PSA value?<?0.5 ng/ml. All patients underwent dynamic PET/CT (dPET/CT) scanning (60 min) of the pelvis and lower abdomen as well as whole-body PET/CT with ⁶⁸Ga-PSMA-11. dPET/CT assessment was based on qualitative evaluation, SUV calculation, and quantitative analysis based on a two-tissue compartment model and a non-compartmental approach leading to the extraction of fractal dimension (FD).

Results

22/31 patients (71.0 %) were ⁶⁸Ga-PSMA-11-positive, while 9/31 (29.0 %) patients were ⁶⁸Ga-PSMA-11-negative. The median PSA value in the ⁶⁸Ga-PSMA-11-positive group was significantly higher (median?=?2.35 ng/mL; range?=?0.19 – 130.0 ng/mL) than in the ⁶⁸Ga-PSMA-11-negative group (median value: 0.34 ng/mL; range?=?0.10 – 4.20 ng/mL). A total of 76 lesions were semi-quantitatively evaluated. PC recurrence-associated lesions demonstrated a mean SUV_average?=?12.4 (median?=?9.0; range?=?2.2 – 84.5) and mean SUV_max = 18.8 (median?=?14.1; range?=?3.1 – 120.3). Dynamic PET/CT studies of the pelvis revealed the following mean values for the PC recurrence-suspicious lesions: K₁?=?0.26, k₃?=?0.30, influx?=?0.14 and FD?=?1.24. Time–activity curves derived from PC-recurrence indicative lesions revealed an increasing ⁶⁸Ga-PSMA-11 accumulation during dynamic PET acquisition. Correlation analysis revealed a moderate, but significant, correlation between PSA levels and the number of lesions detected on ⁶⁸Ga-PSMA-11 PET/CT (r?=?0.54) and between PSA levels and SUV_average (r?=?0.48) or SUV_max (r?=?0.44).

Conclusions

Ga-PSMA-11 PET/CT demonstrated an overall detection rate of 71.0 % 60 min p.i. of the radiotracer in a mixed patient population with respect to PSA levels and including patients with very low PSA values. Higher PSA values were associated with a higher detection rate. The tracer uptake in PC-recurrence-indicative lesions is increasing during the 60 minutes of dynamic PET acquisition.

     

Comparison of <Superscript>68</Superscript>Ga-labelled PSMA-11 and <Superscript>11</Superscript>C-choline in the detection of prostate cancer metastases by PET/CT

Purpose

Prostate-specific membrane antigen (PSMA) is expressed ubiquitously on the membrane of most prostate tumors and its metastasis. While PET/CT using ¹¹C-choline was considered as the gold standard in the staging of prostate cancer, PET with radiolabelled PSMA ligands was introduced into the clinic in recent years. Our aim was to compare the PSMA ligand ⁶⁸Ga-PSMA-11 with ¹¹C-choline in patients with primary and recurrent prostate cancer.

Methods

123 patients underwent a whole-body PET/CT examination using ⁶⁸Ga-PSMA-11 and ¹¹C-choline. Suspicious lesions were evaluated visually and semiquantitatively (SUVavg). Out of these, 103 suffered from a confirmed biochemical relapse after prostatectomy and/or radiotherapy (mean PSA level of 4.5 ng/ml), while 20 patients underwent primary staging.

Results

In 67 patients with biochemical relapse, we detected 458 lymph nodes suspicious for metastasis. PET using ⁶⁸Ga-PSMA-11 showed a significantly higher uptake and detection rate than ¹¹C-choline PET. Also ⁶⁸Ga-PSMA-11 PET identified significantly more patients with suspicious lymph nodes as well as affected lymph nodes regions especially at low PSA levels. Bone lesions suspicious for prostate cancer metastasis were revealed in 36 patients’ biochemical relapse. Significantly more bone lesions were detected by ⁶⁸Ga-PSMA-11, but only 3 patients had only PSMA-positive bone lesions. Nevertheless, we detected also 29 suspicious lymph nodes and 8 bone lesions, which were only positive as per ¹¹C-choline PET. These findings led to crucial differences in the TNM classification and the identification of oligometastatic patients. In the patients who underwent initial staging, all primary tumors showed uptake of both tracers. Although significantly more suspicious lymph nodes and bone lesions were identified, only 2 patients presented with bone lesions only detected by ⁶⁸Ga-PSMA-11 PET.

Conclusion

Thus, PET using ⁶⁸Ga-PSMA-11 showed a higher detection rate than ¹¹C-choline PET for lymph nodes as well as bone lesions. However, we found lymph nodes and bone lesions which were not concordant applying both tracers.

     

Evaluation of primary prostate cancer using <Superscript>11</Superscript>C-methionine-PET/CT and <Superscript>18</Superscript>F-FDG-PET/CT

Objective  

The objective of this study was to evaluate the capability of ¹¹C-methionine (MET)-PET/CT and ¹⁸F-2-deoxy-2-fluoro-d-glucose (FDG)-PET/CT to diagnose primary prostate cancer using recently developed Gemini TF PET/CT (Philips Healthcare, Cleveland, OH).     

<Superscript>11</Superscript>C-acetate PET in the early evaluation of prostate cancer recurrence

Purpose The first aim of the study was to investigate the diagnostic potential of ¹¹C-acetate PET in the early detection of prostate cancer recurrence. A second aim was the evaluation of early and late PET in this context. Methods The study population comprised 32 prostate cancer patients with early evidence of relapse after initial radiotherapy (group A) or radical surgery (group B). The median PSA of group A (n=17) patients was 6 ng/ml (range 2.6–30.2) while that of group B (n=15) was 0.4 ng/ml (range 0.08–4.8). Pelvic-abdominal-thoracic PET was started 2 min after injection of ¹¹C-acetate and evaluated after fusion with CT. Results Group A: Taking a SUV_max≥2 as the cut-off, PET showed local recurrences in 14/17 patients and two equivocal results. Distant disease was observed in six patients and an equivocal result was obtained in one. Endorectal MRI was positive in 12/12 patients. Biopsy confirmed local recurrence in six of six (100%) patients. PET was positive in five of the six patients with biopsy-proven recurrences, the result in the remaining patient being equivocal. Group B: Among the 15 patients, visual interpretation was positive for local recurrences in five patients and equivocal in four. One obturator lymph node was positive. Endorectal MRI was positive in 11/15 patients and equivocal in two. Positional correlation of positive/equivocal results on PET and endorectal MRI was observed in seven of nine patients. PSA decreased significantly after salvage radiotherapy in 8/14 patients, providing strong evidence for local recurrence. PET of the eight patients responding to RT was positive in three and equivocal in two. Conclusion ¹¹C-acetate PET was found to be valuable in the early evaluation of prostate cancer relapse. Optimising scanning time and use of modern PET-CT equipment might allow further improvement.     

<Superscript>11</Superscript>C-methionine PET/CT findings in benign brain disease

¹¹C-methionine (MET) is one of the most commonly used positron emission tomography (PET) tracers for evaluation of malignant brain tumor, with MET-PET being a sensitive technique for visualization of primary and recurrent malignant brain tumors. However, previous reports have demonstrated MET uptake in lesions associated with benign brain diseases. These diseases usually show an increase in MET uptake similar to that of malignant tumors. This pitfall in MET-PET image interpretation is important not only for nuclear medicine professionals, but also for radiologists. In this review, we demonstrate the imaging characteristics of MET uptake in benign brain disease, and recommend physician interpretation of imaging findings and disease characteristics for optimal patient management. Benign uptake must be identified to prevent misdiagnosis and unnecessary surgical operations.     

<Superscript>68</Superscript>Ga-PSMA PET/CT in the evaluation of bone metastases in prostate cancer

Purpose

The aims of this retrospective analysis were to compare ⁶⁸Ga-PSMA PET findings and low-dose CT findings (120 kV, 30 mA), and to obtain semiquantitative and quantitative ⁶⁸Ga-PSMA PET data in patients with prostate cancer (PC) bone metastases.

Methods

In total, 152 PET/CT scans from 140 patients were evaluated. Of these patients, 30 had previously untreated primary PC, and 110 had biochemical relapse after treatment of primary PC. All patients underwent dynamic PET/CT scanning of the pelvis and lower abdomen as well as whole-body PET/CT with ⁶⁸Ga-PSMA-11. The PET/CT scans were analysed qualitatively (visually), semiquantitatively (SUV), and quantitatively based on a two-tissue compartment model and a noncompartmental approach leading to the extraction of the fractal dimension. Differences were considered significant for p values <0.05.

Results

In total, 168 ⁶⁸Ga-PSMA-positive and 113 CT-positive skeletal lesions were detected in 37 patients (8 with primary PC, 29 with biochemical recurrence). Of these 168 lesions, 103 were both ⁶⁸Ga-PSMA PET-positive and CT-positive, 65 were only ⁶⁸Ga-PSMA-positive, and 10 were only CT-positive. The Yang test showed that there were significantly more ⁶⁸Ga-PSMA PET-positive lesions than CT-positive lesions. Association analysis showed that PSA plasma levels were significantly correlated with several ⁶⁸Ga-PSMA-11-associated parameters in bone metastases, including the degree of tracer uptake (SUV_average and SUV_max), its transport rate from plasma to the interstitial/intracellular compartment (K₁), its rate of binding to the PSMA receptor and its internalization (k₃), its influx rate (K_i), and its distribution heterogeneity.

Conclusion

⁶⁸Ga-PSMA PET/CT is a useful diagnostic tool in the detection of bone metastases in PC. ⁶⁸Ga-PSMA PET visualizes more bone metastases than low-dose CT. PSA plasma levels are significantly correlated with several ⁶⁸Ga-PSMA PET parameters.

     

Liver metastases from prostate cancer at 11C-Choline PET/CT: a multicenter,retrospective analysis

Aim

During our daily clinical practice using 11C-Choline PET/CT for restaging patients affected by relapsing prostate cancer (rPCa) we noticed an unusual but significant occurrence of hypodense hepatic lesions with a different tracer uptake. Thus, we decided to evaluate the possible correlation between rPCa and these lesions as possible hepatic metastases.

Materials and methods

We retrospectively enrolled 542 patients diagnosed with rPCa in biochemical relapse after a radical treatment (surgery and/or radiotherapy). Among these, patients with a second tumor or other benign hepatic diseases were excluded. All patients underwent 11C-Choline PET/CT during the standard restaging workup of their disease. We analyzed CT images to evaluate the presence of hypodense lesions and PET images to identify the relative tracer uptake. In accordance to the subsequent oncological history, five clinical scenarios were recognized [Table 1]: normal low dose CT (ldCT) and normal tracer distribution (Group A); evidence of previously unknown hepatic round hypodense areas at ldCT with normal rim uptake (Group B); evidence of previously known hepatic round hypodense areas at ldCT stable over time and with normal rim uptake (Group C); evidence of previously known hepatic round hypodense areas at ldCT, in a previous PET/CT scan, with or without rim uptake and significantly changing over time in terms of size and/or uptake (Group D); evidence of hepatic round hypodense areas at ldCT with or without rim uptake confirmed as prostate liver metastases by histopathology, triple phase ceCT, ce-ultra sound (CEUS) and clinical/biochemical evaluation (Group E). We evaluated the correlation with PSA level at time of scan, rim SUVmax and association with local relapse or non-hepatic metastases (lymph nodes, bone, other parenchyma).

Results

Five hundred and forty-two consecutive patients were retrospectively enrolled. In 140 of the 542 patients more than one 11C-choline PET/CT had been performed. A total of 742 11C-Choline PET/CT scans were analyzed. Of the 542 patients enrolled, 456 (84.1%) had a normal appearance of the liver both at ldCT and PET (Group A). 19/542 (3,5%) belonged to Group B, 13/542 (2.4%) to Group C, 37/542 (6.8%) to Group D and 18/542 (3.3%) to Group E. Mean SUVmax of the rim was: 4.5 for Group B; 4.2 for Group C; 4.8 for Group D; 5.9 for Group E. Mean PSA level was 5.27 for Group A, 7.9 for Group B, 10.04 for Group C, 10.01 for Group D, 9.36 for Group E. Presence of positive findings at 11C-Choline PET/CT in any further anatomical area (local relapse, lymph node, bone, other extra hepatic sites) correlated with an higher PSA (p?=?0.0285). In both the univariate and multivariate binary logistic regression analyses. PSA, SUVmax of the rim, local relapse, positive nodes were not associated to liver mets (Groups D-E) (p?>?0.05). On the contrary, a significant correlation was found between the presence of liver metG (group D-E) and bone lesions (

Conclusion

Our results indicate that liver metastases in relapsing prostate cancer may occur frequently. The real incidence evaluation needs more investigations. In this case and despite technical limitations, Choline PET/CT shows alterations of tracer distribution within the liver that could eventually be mistaken for simple cysts but can be suspected when associated to high trigger PSA, concomitant bone lesions or modification over time. In this clinical setting an accurate analysis of liver tracer distribution (increased or decreased uptake) by the nuclear medicine physician is, therefore, mandatory.

     

Acquisition with <Superscript>11</Superscript>C-choline and <Superscript>18</Superscript>F-fluorocholine PET/CT for patients with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

The objective of the systematic review and meta-analysis was to evaluate whether the choice between two radiotracers, ¹¹C-choline (¹¹C-cho) and ¹⁸F-fluorocholine (¹⁸F-FCH) for PET/CT, and different acquisition protocols contributed to detect metastases for patients with biochemical recurrence of prostate cancer after radical prostatectomy or radiotherapy. We searched in January 2016 in Pubmed and Embase for articles that had used radiolabeled choline PET/CT in restaging. The meta-analysis evaluated technical and clinical aspects. Across 18 articles 1 219 of 2 213 patients (54.9 %) had a positive radiolabeled PET/CT image. Mean of the mean/median restaging PSA levels was 3.6 ± 2.7 ng/mL (range 0.5–10.7 ng/mL). Six articles with ¹¹C-cho PET/CT had a radiation activity of 561 ± 122 MBq and it was 293 ± 47 MBq in 12 articles with ¹⁸F-FCH PET/CT. The difference was significant (P = 0.007, t test). Uptake time was 5 min in articles with ¹¹C-cho PET/CT and it was 29 ± 24 min in articles with ¹⁸F-FCH PET/CT. The difference was significant (P = 0.02, t test). Thereby the detection rates of metastatic sites in articles with ¹¹C-cho (30 ± 5 %) and ¹⁸F-FCH (39 ± 5 %) did not differ significantly (P = 0.26, t test). In linear regression analyses of the articles, the radiation activity of ¹¹C-cho and ¹⁸F-FCH was not significantly associated with the detection rate of metastatic sites (P = 0.75 and P = 0.60). Restaging with radiolabeled choline PET/CT detected metastatic sites for patients with biochemical recurrence and PSA levels of 1–10 ng/mL at clinically relevant level. The choice between the two choline radiotracers and different acquisition protocols had no significant impact on detection.     

<Superscript>11</Superscript>C-methylaminoisobutyric acid (MeAIB) PET for evaluation of prostate cancer: compared with <Superscript>18</Superscript>F-fluorodeoxyglucose PET

Objective

α-N-methyl-¹¹C-methylaminoisobutyric acid (¹¹C-MeAIB) is a selective substrate of system A amino acid transport, and known to accumulate in malignant lesions. The aim of this study was to evaluate the utility of MeAIB PET for the assessment of prostate cancer, compared with FDG PET.

Methods

Thirty-four men (age range 57–77 years) with prostate cancer were prospectively enrolled, and underwent MeAIB PET and FDG PET between January 2011 and January 2013. MeAIB PET and FDG PET were performed at 20 and 50 min post-injection, respectively. SUVmax of the prostate was calculated, and visual analysis was conducted for MeAIB and FDG PET studies. MRI images were visually evaluated if available. All patients received total prostatectomy subsequently, and imaging findings were compared with pathological results, including T stage, Gleason score, and tumor size. The patient-based and lesion-based sensitivity and specificity were calculated according to pathological significant cancer.

Results

Mean value of SUVmax of ¹¹C-MeAIB PET and ¹⁸F-FDG PET in prostate cancer were 3.18 (±1.90, range; 1.55–9.57) and 3.88 (±2.85, range; 2.04–14.47). MeAIB PET and FDG PET were positive by visual analysis in 47.1 % (16/34) and 44.1 % (15/34) of the patients. MRI was positive in 51.5 % (17/33). Pathological stage and Gleason score were as follows: Stage 2 (n = 23), 3 (n = 8), and 4 (n = 3); Gleason score 6 (n = 13), 7 (n = 16), 8 (n = 3), and 9 (n = 2). The sensitivities tended to be higher according to higher pathological T stage or Gleason sum score for both MeAIB and FDG PET studies. Visual analysis of both MeAIB PET and FDG PET had significant correlation with extraprostatic extension (p < 0.05). MeAIB PET and FDG PET had complementary results by visual analysis in the assessment of prostate cancer. The patient-based sensitivity of MeAIB PET, FDG PET, and MRI were 51.6, 48.4, and 56.7 %, respectively. The patient-based specificity of these modalities was 100 % for each modality.

Conclusions

MeAIB PET has better diagnostic results than FDG PET for the assessment of significant prostate cancer, and these PET studies showed complementary results. MRI has even better diagnostic results than ¹¹C-MeAIB PET. MeAIB accumulates in prostate cancer, which indicates that the system A amino acid transport pathway is activated in prostate cancer.

     

[<Superscript>11</Superscript>C]choline PET/CT imaging in occult local relapse of prostate cancer after radical prostatectomy

Purpose The aim of this study was to assess the accuracy and clinical impact of [¹¹C]choline PET/CT for localizing occult relapse of prostate adenocarcinoma after radical prostatectomy. Methods Fourty-nine patients with prostate adenocarcinoma, radical prostatectomy, no evidence of metastatic disease, and occult relapse underwent [¹¹C]choline PET/CT. Thirty-six of the patients had biochemical evidence and histological evaluation of local recurrence. Thirteen patients had PSA < 0.3 ng/ml and no evidence of active disease after 1 year follow-up. Focal nodular [¹¹C]choline uptake in the prostatic fossa was visually assessed and graded on a five point scale. Maximum standardized radioactivity uptake value (SUV_max) and the lesion size were measured. A receiver operating characteristic (ROC) analysis was performed and the clinical impact of the PET/CT study was determined. Results [¹¹C]choline PET/CT was true positive in 23/33 patients and true negative in 12/13 controls. SUV_max of local recurrence was 3.0 (median, range 0.6–7.4) and 1.1 (0.4–1.6) in controls (p = 0.0002). Lesion size was 1.7 cm (range 0.9–3.7). Area under the ROC curve for detecting relapse was 0.90 ± 0.05 and 0.83 ± 0.06 for visual evaluation and SUV_max, respectively. Sensitivity and specificity of [¹¹C]choline PET/CT were 0.73 and 0.88, respectively. [¹¹C]choline PET/CT identified 12/17 (71%) patients with a favourable biochemical response to local radiotherapy at 2 year (median, 0.8–3.2 range) follow-up. Conclusions Focally increased [¹¹C]choline uptake in the prostatic bed reliably predicted local low volume occult relapsing prostate adenocarcinoma after radical prostatectomy and identified 71% of patients with a favourable biochemical response to local radiotherapy.     

Comparison of [<Superscript>68</Superscript>Ga]Ga-PSMA-11 PET/CT with [<Superscript>18</Superscript>F]NaF PET/CT in the evaluation of bone metastases in metastatic prostate cancer patients prior to radionuclide therapy

Aim

The purpose of this study was to investigate the diagnostic performance of ⁶⁸Ga-PSMA-11 PET/CT in the evaluation of bone metastases in metastatic prostate cancer (PC) patients scheduled for radionuclide therapy in comparison to [¹⁸F]sodium fluoride (¹⁸F-NaF) PET/CT.

Methods

Sixteen metastatic PC patients with known skeletal metastases, who underwent both ⁶⁸Ga-PSMA-11 PET/CT and ¹⁸F-NaF PET/CT for assessment of metastatic burden prior to radionuclide therapy, were analysed retrospectively. The performance of both tracers was calculated on a lesion-based comparison. Intensity of tracer accumulation of pathologic bone lesions on ¹⁸F-NaF PET and ⁶⁸Ga-PSMA-11 PET was measured with maximum standardized uptake values (SUV_max) and compared to background activity of normal bone. In addition, SUV_max values of PET-positive bone lesions were analysed with respect to morphologic characteristics on CT. Bone metastases were either confirmed by CT or follow-up PET scan.

Results

In contrast to 468 PET-positive lesions suggestive of bone metastases on ¹⁸F-NaF PET, only 351 of the lesions were also judged positive on ⁶⁸Ga-PSMA-11 PET (75.0%). Intensity of tracer accumulation of pathologic skeletal lesions was significantly higher on ¹⁸F-NaF PET compared to ⁶⁸Ga-PSMA-11 PET, showing a median SUV_max of 27.0 and 6.0, respectively (p?<?0.001). Background activity of normal bone was lower on ⁶⁸Ga-PSMA-11 PET, with a median SUV_max of 1.0 in comparison to 2.7 on ¹⁸F-NaF PET; however, tumour to background ratio was significantly higher on ¹⁸F-NaF PET (9.8 versus 5.9 on ⁶⁸Ga-PSMA-11 PET; p?=?0.042). Based on morphologic lesion characterisation on CT, ¹⁸F-NaF PET revealed median SUV_max values of 23.6 for osteosclerotic, 35.0 for osteolytic, and 19.0 for lesions not visible on CT, whereas on ⁶⁸Ga-PSMA-11 PET median SUV_max values of 5.0 in osteosclerotic, 29.5 in osteolytic, and 7.5 in lesions not seen on CT were measured. Intensity of tracer accumulation between¹⁸F-NaF PET and ⁶⁸Ga-PSMA-11 PET was significantly higher in osteosclerotic (p?<?0.001) and lesions not visible on CT (p?=?0.012).

Conclusion

In comparison to ⁶⁸Ga-PSMA-11 PET/CT, ¹⁸F-NaF PET/CT detects a higher number of pathologic bone lesions in advanced stage PC patients scheduled for radionuclide therapy. Our data suggest that ⁶⁸Ga-PSMA-11 PET should be combined with ¹⁸F-NaF PET in PC patients with skeletal metastases for restaging prior to initiation or modification of therapy.