Three-phase 18F-fluorocholine PET/CT in the evaluation of prostate cancer recurrence

Dual-phase 68Ga-PSMA-11 PET/CT may increase the rate of detected lesions in prostate cancer patients

BACKGROUND

This study was conducted to compare the early static (3-6 min post-injection (p.i.)) and standard whole body (1 h, p.i.) 68Ga-PSMA-11 PET/CT imaging for detection of lesions in prostate cancer (PC) patients.

MATERIALS AND METHODS

In this study, PC patients suspected of recurrence underwent 68Ga-PSMA-11 PET/CT. Early static images were acquired from the pelvis and the lower abdomen 3-5 minutes after radiotracer injection and, a routine whole body scan was performed from the skull to the mid-thigh 1 h after injection. Quantitative analysis (SUVmax) was evaluated in suspicious lesions.

RESULTS

Of 19 evaluated PC patients with a median age of 72 ± 1.66 years (range: 55-85 years) and prostate-specific antigen (PSA) of 1.72 ± 6.11 ng/ml (range: 0.1-100 ng/ml) (median ± SE), 16 showed positive in the whole body PET/CT. All of the patients with positive whole body scans due to pelvic involvement had positive early scan results. Totally, 22 lesions were detected in both early and delay scans in the pelvic which 16 were related to prostate involvement, 4 were related to lymph node involvement, and 2 were related to bone involvement. Moreover, in addition to the mentioned 22 lesions, early PET imaging successfully detected local recurrence in a patient who was negative on WB PET/ CT; this lesion was masked in the delay scan due to bladder activity. The median SUVmax values of the early and delay scans were 3.69 ± 1.07 (median ± SE) (range: 1.2-14.5) and 5.85 ± 1.69 (range: 3.1-23.4), respectively. (p = 0.005).

CONCLUSION

Early static 68Ga-PSMA-11 PET/CT imaging might discriminate metastases from urinary bladder activity. Therefore, early static imaging in combination with whole body 60-min p.i. imaging can improve the detection of local involvement pelvic disease.

Recurrent prostate cancer after radical prostatectomy: restaging performance of 18F-choline hybrid PET/MRI

To evaluate the diagnostic performance of a whole-body 18F-choline (FCH) hybrid PET/MRI for prostate cancer patients at biochemical relapse after radical prostatectomy (RP) compared to pelvic multiparametric MRI (mpMRI), one of the standard imaging modality for this patient population. From 2010 to 2016, 58 whole-body FCH PET/MRI studies with mpMRI acquisitions were performed in 53 prostate cancer patients relapsing after curative RP. Median PSA and PSA doubling time (PSA DT) at PET study were 1.5 ng/ml and 6.5 months, respectively. The overall positivity rate of FCH PET/MRI was 58.6% (n = 34), dropping to 44% in patients with a PSA ≤ 2 ng/ml (n = 36). Median PSA values in positive and negative PET/MRI studies were 2.2 ng/ml and 0.8 ng/ml, respectively, with no differences in PSA DT (6.5 vs. 6.6 months). A PSA value ≥ 1.5 ng/ml was a significant predictor of positivity on PET/MRI studies. Compared to PET, mpMRI identified more local relapses (17 vs. 14, p = 0.453) while PET outperformed whole-body Dixon MRI for regional (16 vs. 9, p = 0.016) and distant (12 vs. 6, p = 0.031) metastases. Compared to pelvic mpMRI, the treatment approach turned out to be influenced more frequently using whole-body FCH hybrid PET/MRI studies (58.6% vs. 38%). In prostate cancer patients with biochemical recurrence after RP, whole-body FCH PET/MRI achieved a higher detection rate of nodal/distant metastases compared to pelvic mpMRI alone, increasing the change of treatment strategy by more than 20%.

Validation of the physiological background correction method for the suppression of the spill-in effect near highly radioactive regions in positron emission tomography

Background

Positron emission tomography (PET) imaging has a wide applicability in oncology, cardiology and neurology. However, a major drawback when imaging very active regions such as the bladder is the spill-in effect, leading to inaccurate quantification and obscured visualisation of nearby lesions. Therefore, this study aims at investigating and correcting for the spill-in effect from high-activity regions to the surroundings as a function of activity in the hot region, lesion size and location, system resolution and application of post-filtering using a recently proposed background correction technique. This study involves analytical simulations for the digital XCAT2 phantom and validation acquiring NEMA phantom and patient data with the GE Signa PET/MR scanner. Reconstructions were done using the ordered subset expectation maximisation (OSEM) algorithm. Dedicated point-spread function (OSEM+PSF) and a recently proposed background correction (OSEM+PSF+BC) were incorporated into the reconstruction for spill-in correction. The standardised uptake values (SUV) were compared for all reconstruction algorithms.

Results

The simulation study revealed that lesions within 15–20 mm from the hot region were predominantly affected by the spill-in effect, leading to an increased bias and impaired lesion visualisation within the region. For OSEM, lesion SUV_max converged to the true value at low bladder activity, but as activity increased, there was an overestimation as much as 19% for proximal lesions (distance around 15–20 mm from the bladder edge) and 2–4% for distant lesions (distance larger than 20 mm from the bladder edge). As bladder SUV increases, the % SUV change for proximal lesions is about 31% and 6% for SUV_max and SUV_mean, respectively, showing that the spill-in effect is more evident for the SUV_max than the SUV_mean. Also, the application of post-filtering resulted in up to 65% increment in the spill-in effect around the bladder edges. For proximal lesions, PSF has no major improvement over OSEM because of the spill-in effect, coupled with the blurring effect by post-filtering. Within two voxels around the bladder, the spill-in effect in OSEM is 42% (32%), while for OSEM+PSF, it is 31% (19%), with (and without) post-filtering, respectively. But with OSEM+PSF+BC, the spill-in contribution from the bladder was relatively low (below 5%, either with or without post-filtering). These results were further validated using the NEMA phantom and patient data for which OSEM+PSF+BC showed about 70–80% spill-in reduction around the bladder edges and increased contrast-to-noise ratio up to 36% compared to OSEM and OSEM+PSF reconstructions without post-filtering.

Conclusion

The spill-in effect is dependent on the activity in the hot region, lesion size and location, as well as post-filtering; and this is more evident in SUV_max than SUV_mean. However, the recently proposed background correction method facilitates stability in quantification and enhances the contrast in lesions with low uptake.

Electronic supplementary material

The online version of this article (10.1186/s40658-018-0233-8) contains supplementary material, which is available to authorized users.

68Ga-PSMA and 11C-Choline comparison using a tri-modality PET/CT-MRI (3.0 T) system with a dedicated shuttle

Background

The aim of this study was to prospectively compare the detection rate of ⁶⁸Ga-PSMA versus ¹¹C-Choline in men with prostate cancer with biochemical recurrence and to demonstrate the added value of a tri-modality PET/CT-MRI system.

Methods

We analysed 36 patients who underwent both ¹¹C-Choline PET/CT and ⁶⁸Ga-PSMA PET/CT scanning within a time window of 1-2 weeks. Additionally, for the ⁶⁸Ga-PSMA scan, we used a PET/CT-MRI (3.0 T) system with a dedicated shuttle, acquiring MRI images of the pelvis.

Results

Both scans were positive in 18 patients (50%) and negative in 8 patients (22%). Nine patients were positive with ⁶⁸Ga-PSMA alone (25%) and one with ¹¹C-Choline only (3%). The median detected lesion per patient was 2 for ⁶⁸Ga-PSMA (range 0-93) and 1 for ¹¹C-Choline (range 0-57). Tumour to background ratios in all concordant lesions (n = 96) were higher for ⁶⁸Ga-PSMA than for ¹¹C-Choline (110.3 ± 107.8 and 27.5 ± 17.1, mean ± S.D., for each tracer, respectively P = 0.0001). The number of detected lesions per patient was higher for ¹¹C-Choline in those with PSA ≥ 3.3 ng/mL, while the number of detected lesions was independent of PSA levels for ⁶⁸Ga-PSMA using the same PSA cut-off value. Metastatic pelvic lesions were found in 25 patients (69%) with ⁶⁸Ga-PSMA PET/CT, in 18 (50%) with ¹¹C-Choline PET/CT and in 21 (58%) with MRI (3.0 T). MRI was very useful in detecting recurrence in cases classified as indeterminate by means of PET/CT alone at prostate bed.

Conclusions

In patients with prostate cancer with biochemical recurrence ⁶⁸Ga-PSMA detected more lesions per patient than ¹¹C-Choline, regardless of PSA levels. PET/CT-MRI (3.0 T) system is a feasible imaging modality that potentially adds useful relevant information with increased accuracy of diagnosis.

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.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography May Exclude Malignancy in Sonographically Suspicious and Scintigraphically Hypofunctional Thyroid Nodules and Reduce Unnecessary Thyroid Surgeries

BACKGROUND

The aim of this study was to evaluate whether ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is useful in the further characterization of sonographically suspicious and scintigraphically hypofunctional thyroid nodules.

METHODS

Sixty-five patients with sonographically suspicious thyroid nodules that were hypofunctional on 99m-Tc-pertechnetate scintigraphy (diameter >1 cm) were retrospectively analyzed. All patients underwent evaluation with FDG-PET/CT. Thyroid nodules were sonographically categorized by Thyroid Image Reporting and Data System (TIRADS) criteria. FDG uptake in the thyroid nodules was visually compared to the remainder of the thyroid tissue and categorized as pathological or non-pathological. In cases of pathologically increased uptake, maximum standardized uptake values (SUVmax) of the suspicious nodule and the perinodular thyroid tissue were determined. Depending on the results of the FDG-PET/CT, patients underwent thyroid surgery (pathological FDG uptake) or follow-up examinations (non-pathological FDG uptake). The endpoints for comparison with the FDG uptake were either histological results or sonographic follow-up examinations of at least five years.

RESULTS

In 18/65 (28%) patients, PET/CT showed visually pathological FDG uptake in the suspicious thyroid nodules (SUVmax 7.1 ± 4.6). Of these nodules, 3/18 (17%) were sonographically categorized as TIRADS 4a, 11/18 (61%) nodules as TIRADS 4b, 3/18 (17%) nodules as TIRADS 4c, and 1/18 (6%) nodule as TIRADS 5. The other nodules without pathological FDG uptake were categorized as TIRADS 4a in 24/47 (51%) patients, as TIRADS 4b in 18/47 (38%), and as TIRADS 4c in 5/47 (11%) patients. Twenty-three patients (18 FDG positive, 5 FDG negative) underwent surgery. The other patients underwent follow-up examinations with stability on observation over at least five years as a surrogate endpoint. Taking into consideration that FDG-PET/CT was rated as true negative in 42/47 patients with stability on sonographic follow-up, sensitivity, specificity, positive predictive value, and negative predictive value of FDG-PET/CT in detecting malignancy in the suspicious thyroid nodules were 100%, 87%, 61%, and 100%, respectively.

CONCLUSION

FDG-PET/CT allows stratification of patients with sonographically suspicious and scintigraphically hypofunctional thyroid nodules with a positive predictive value of 61% and negative predictive value of 100%. The absence of visually pathological FDG uptake in suspicious thyroid nodules may be useful for avoiding unnecessary thyroid surgery.

PET and PET/CT with radiolabeled choline in prostate cancer: a critical reappraisal of 20 years of clinical studies

We here aim to provide a comprehensive and critical review of the literature concerning the clinical applications of positron emission tomography/computed tomography (PET/CT) with radiolabeled choline in patients with prostate cancer (PCa). We will initially briefly summarize the historical context that brought to the synthesis of [¹¹C]choline, which occurred exactly 20 years ago. We have arbitrarily grouped the clinical studies in three different periods, according to the year in which they were published and according to their relation with their applications in urology, radiotherapy and oncology. Studies at initial staging and, more extensively, studies in patients with biochemical failure, as well as factors predicting positive PET/CT will be reviewed. The capability of PET/CT with radiolabeled choline to provide prognostic information on PCa-specific survival will also be examined. The last sections will be devoted to the use of radiolabeled choline for monitoring the response to androgen deprivation therapy, radiotherapy, and chemotherapy. The accuracy and the limits of the technique will be discussed according to the information available from standard validation processes, including biopsy or histology. The clinical impact of the technique will be discussed on the basis of changes induced in the management of patients and in the evaluation of the response to therapy. Current indications to PET/CT, as officially endorsed by guidelines, or as routinely performed in the clinical practice will be illustrated. Emphasis will be made on methodological factors that might have influenced the results of the studies or their interpretation. Finally, we will briefly highlight the potential role of positron emission tomography/magnetic resonance and of new radiotracers for PCa imaging.

18F-Choline PET/CT scan in staging and biochemical recurrence in prostate cancer patients: Changes in classification and radiotherapy planning

OBJECTIVE

To evaluate the role of the ¹⁸F-Choline PET/CT in prostate cancer management when detecting distant disease in planning radiotherapy and staging and to evaluate the therapy changes guided by PET/TC results.

MATERIAL AND METHODS

A retrospective evaluation was performed on ¹⁸F-Choline PET/CT scans of patients with prostate cancer. Staging and planning radiotherapy scans were selected in patients with at least 9 months follow up. There was a total of 56 studies, 33 (58.93%) for staging, and 23 (41.07%) for planning radiotherapy. All scans were obtained using a hybrid PET/CT scanner. The PET/CT acquisition protocol consisted of a dual-phase procedure after the administration of an intravenous injection of 296-370MBq of ¹⁸F-Choline.

RESULTS

There were 43 out of 56 (76.8%) scans considered as positive, and 13 (23.2%) were negative. The TNM staging was changed in 13 (23.2%) scans. The PET/CT findings ruled out distant disease in 4 out of 13 scans, and unknown distant disease was detected in 9 (69.3%) scans.

CONCLUSIONS

¹⁸F-Choline PET/CT is a useful technique for detecting unknown distant disease in prostate cancer when staging and planning radiotherapy. The inclusion of ¹⁸F-choline PET/CT should be considered in prostate cancer management protocols.

Imaging of Prostate Cancer Using 18F-Choline PET/Computed Tomography

¹⁸F-fluorocholine (FCH) PET/computed tomography (CT) is a valuable imaging modality in prostate cancer disease. Probably, its main role is restaging of patients with biochemical recurrence after radical prostatectomy or external beam radiotherapy. ¹⁸F-FCH PET/CT is strengthening its position in the initial staging, biopsy target definition, radiotherapy planning, and therapy monitoring. Gleason score and prostate-specific antigen value, doubling time, and velocity can influence positivity of ¹⁸F-FCH PET/CT. The influence of androgen deprivation therapy on choline uptake is not precisely clarified. Collaboration between nuclear medicine physicians, radiologists, urologists, oncologists, and radiotherapists is crucial to help patients with prostate cancer disease.

Clinical Utility of Gallium-68 PSMA PET/CT Scan for Prostate Cancer

BACKGROUND

Prostate cancer is biologically and clinically a heterogeneous disease that makes imaging evaluation challenging. One of the important challenges in this cancer is to detect recurrent disease. Biochemical response using Prostate Specific Antigen (PSA) and Imaging using several PET tracers have poor sensitivity and specificity. Therefore, we analyse the role of Ga68-PSMA (Prostate Specific Membrane Antigen) imaging in prostate cancer, which is a new PET tracer.

METHODS

In this study, we evaluated PET scans of 262 patients with diagnosis of prostate cancer. These patients were scanned using Ga68-PSMA for either staging or response evaluation.

RESULTS

336 PSMA scans were performed. Ga68-PSMA scan resulted in the detection of extra-prostatic disease in 53.2% of cases when done at baseline before commencing any treatment. The sensitivity of Ga68-PSMA at baseline with histopathological diagnosis was 95% with 95% CI ranging from 86% to 98%. The positive predictive value was high at 98% with 95% CI ranging from 91% to 99%. In 26 (10%) patients who had surgical castration, Ga68-PSMA scan was able to detect disease progression / castration resistance in 100% of cases. The outcome of castration-resistant prostate cancer was compared with other cases where castration was not done. In those who did not undergo castration, there was a significantly better response by hormone therapy (p = 0.03) and radiotherapy (p = 0.01) on Ga68-PSMA. The sensitivity of Ga68-PSMA response with biochemical response was 66.7% with 95% CI ranging between 46 %- 82.7%. Ga68-PSMA response did not correlate with biochemical response.

CONCLUSION

Ga68-PSMA has good sensitivity for diagnosis, staging, restaging, evaluation of therapy response and prognostication in prostate cancer.

Early dynamic imaging in 68Ga- PSMA-11 PET/CT allows discrimination of urinary bladder activity and prostate cancer lesions

PURPOSE

PET/CT with ⁶⁸Ga-labelled prostate-specific membrane antigen (PSMA)-ligands has been proven to establish a promising imaging modality in the work-up of prostate cancer (PC) patients with biochemical relapse. Despite a high overall detection rate, the visualisation of local recurrence may be hampered by high physiologic tracer accumulation in the urinary bladder on whole body imaging, usually starting 60 min after injection. This study sought to verify whether early dynamic ⁶⁸Ga-PSMA-11 (HBED-CC)PET/CT can differentiate pathologic PC-related tracer uptake from physiologic tracer accumulation in the urinary bladder.

METHODS

Eighty consecutive PC patients referred to ⁶⁸Ga -PSMA-11 PET/CT were included in this retrospective analysis (biochemical relapse: n = 64; primary staging: n = 8; evaluation of therapy response/restaging: n = 8). In addition to whole-body PET/CT acquisition 60 min post injection early dynamic imaging of the pelvis in the first 8 min after tracer injection was performed. SUV_max of pathologic lesions was calculated and time-activity curves were generated and compared to those of urinary bladder and areas of physiologic tracer uptake.

RESULTS

A total of 55 lesions consistent with malignancy on 60 min whole body imaging exhibited also pathologic ⁶⁸Ga-PSMA-11 uptake during early dynamic imaging (prostatic bed/prostate gland: n = 27; lymph nodes: n = 12; bone: n = 16). All pathologic lesions showed tracer uptake within the first 3 min, whereas urinary bladder activity was absent within the first 3 min of dynamic imaging in all patients. Suv_max was significantly higher in PC lesions in the first 6 min compared to urinary bladder accumulation (p < 0.001). In the subgroup of PC patients with biochemical relapse the detection rate of local recurrence could be increased from 20.3 to 29.7%.

CONCLUSIONS

Early dynamic imaging in ⁶⁸Ga-PSMA-11 PET/CT reliably enables the differentiation of pathologic tracer uptake in PC lesions from physiologic bladder accumulation. Performance of early dynamic imaging in addition to whole body imaging 60 min after tracer injection might improve the detection rate of local recurrence in PC patients with biochemical relapse referred for ⁶⁸Ga-PSMA-11 PET/CT.

Imaging on nodal staging of prostate cancer

Prostate cancer is the second most common cancer in men and is the second highest cause of cancer death in men of all races. Accurate lymph node staging is essential to ensure adequate treatment of prostate cancer. Historically, conventional imaging methods have demonstrated limited sensitivity and specificity in the detection of lymph node metastases. There are many emerging PET tracers that have recently proven to be effective. In addition, the use of ultrasmall iron oxide nanoparticle-enhanced MRI has demonstrated promising results. This review outlines the strengths and limitations of each of the different imaging modalities as well as individual tracers used, including preclinical and clinical agents.

Optimized protocol for (18)F-choline PET/CT in patients with biochemically relapsed prostate cancer: experiences on 250 consecutive cases

PURPOSE

We review acquisition F-choline PET/CT methodology, evaluate a new F-choline acquisition protocol for prostate cancer (PC), and propose a standardized acquisition protocol on F-choline in PC patients.

MATERIALS

Two hundred fifty consecutive PC patients (mean age 72 years, mean PSA 7.9 ng/mL) were prospectively evaluated with F-choline PET/CT. An early scan of the pelvis (1 bed position of 4 minutes) was followed by a whole-body scan at 1 hour. Early and 1 delayed hour images of the pelvis were compared.

RESULTS

Twenty-one percent of patients (n = 57) with positive F-choline demonstrated abnormal local uptake; 18% of patients (n = 45) showed distant localization only; 23% of patients (n = 53) had both local and distant localization; 38% of patients (n = 38) did not show any pathological uptake. All early images showed absence of radioactive urine in ureters, bladder, or urethra with satisfactory visualization of the prostatic region. Considering the group of patients with local uptake only, the prostatic region uptake, confirmed by late images, was better visualized in the early phase in 32/57 cases (SUVmax 12.4 ± 3.2 vs. 7.3 ± 5.2, P <0.01). Instead distant lesions were visualized on both early and late images with similar uptakes values (SUVmax 9.8 ± 4.1 vs. 10.3 ± 4.5, P = N.S.).

CONCLUSION

Early F-choline images improve pelvic prostate cancer lesion clarity. All pathologic pelvic deposits (prostate, lymph nodes, bone) were visualized both in the early and late images.

Comparison of meta-analyses among elastosonography (ES) and positron emission tomography/computed tomography (PET/CT) imaging techniques in the application of prostate cancer diagnosis

The early diagnosis of prostate cancer (PCa) appears to be of vital significance for the provision of appropriate treatment programs. Even though several sophisticated imaging techniques such as positron emission tomography/computed tomography (PET/CT) and elastosonography (ES) have already been developed for PCa diagnosis, the diagnostic accuracy of these imaging techniques is still controversial to some extent. Therefore, a comprehensive meta-analysis in this study was performed to compare the accuracy of various diagnostic imaging methods for PCa, including 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine PET/CT, 18F-fluoroglucose PET/CT, transrectal real-time elastosonography (TRTE), and shear-wave elastosonography (SWE). The eligible studies were identified through systematical searching for the literature in electronic databases including PubMed, Cochrane, and Web of Science. On the basis of the fixed-effects model, the pooled sensitivity (SEN), specificity (SPE), and area under the receiver operating characteristics curve (AUC) were calculated to estimate the diagnostic accuracy of 11C-choline PET/CT, 11C-acetate PET/CT, 18F-fluorocholine (FCH) PET/CT, 18F-fluoroglucose (FDG) PET/CT, TRTE, and SWE. All the statistical analyses were conducted with R language Software. The present meta-analysis incorporating a total of 82 studies demonstrated that the pooled sensitivity of the six imaging techniques were sorted as follows: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT; the pooled specificity were also compared: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 18F-FDG PET/CT > 11C-acetate PET/CT; finally, the pooled diagnostic accuracy of the six imaging techniques based on AUC were ranked as below: SWE > 18F-FCH PET/CT > 11C-choline PET/CT > TRTE > 11C-acetate PET/CT > 18F-FDG PET/CT. SWE and 18F-FCH PET/CT imaging could offer more assistance in the early diagnosis of PCa than any other studied imaging techniques. However, the diagnostic ranking of the six imaging techniques might not be applicable to the clinical phase due to the shortage of stratified analysis.

Assessment of Lymph Nodes and Prostate Status Using Early Dynamic Curves with (18)F-Choline PET/CT in Prostate Cancer

Introduction

Dynamic image acquisition with ¹⁸F-Choline [fluorocholine (FCH)] PET/CT in prostate cancer is mostly used to overcome the bladder repletion, which could obstruct the loco-regional analysis. The aim of our study was to analyze early dynamic FCH acquisitions to define pelvic lymph node or prostate pathological status.

Material and methods

Retrospective analysis was performed on 39 patients for initial staging (n = 18), or after initial treatment (n = 21). Patients underwent 10-min dynamic acquisitions centered on the pelvis, after injection of 3–4 MBq/kg of FCH. Whole-body images were acquired about 1 h after injection using a PET/CT GE Discovery LS (GE-LS) or Siemens Biograph mCT (mCT). Maximum and mean SUV according to time were measured on nodal and prostatic lesions. SUV_mean was corrected for partial volume effect (PVEC) with suitable recovery coefficients. The status of each lesion was based on histological results or patient follow-up (>6 months). A Mann–Whitney test and ANOVA were used to compare mean and receiver operating characteristic (ROC) curve analysis.

Results

The median PSA was 8.46 ng/mL and the median Gleason score was 3 + 4. Ninety-two lesions (43 lymph nodes and 49 prostate lesions) were analyzed, including 63 malignant lesions. In early dynamic acquisitions, the maximum and mean SUV were significantly higher, respectively, on mCT and GE-LS, in malignant versus benign lesions (p < 0.001, p < 0.001). Mean SUV without PVEC, allowed better discrimination of benign from malignant lesions, in comparison with maximum and mean SUV (with PVEC), for both early and late acquisitions. For patients acquired on mCT, area under the ROC curve showed a trend to better sensitivity and specificity for early acquisitions, compared with late acquisitions (SUVmax AUC 0.92 versus 0.85, respectively).

Conclusion

Assessment of lymph nodes and prostate pathological status with early dynamic imaging using PET/CT FCH allowed prostate cancer detection in situations where proof of malignancy is difficult to obtain.

Significance of 18F-fluorocholine PET/CT positive pulmonary lesions in prostate cancer patients

AIM

To assess the frequency and the significance of incidental pulmonary lesions with 18F-fluorocholine (18F-FCH) PET/CT in prostate cancer (PCa) patients.

PATIENTS, METHODS

225 consecutive PCa patients referred for 18F-FCH PET/CT (median age 68 years) were retrospectively evaluated for the presence of lesions in the lungs: 173 referred for restaging and 52 for initial staging regarding their high risk of extra prostatic extension. The final diagnosis was based on histopathological or on clinical and radiological follow-up.

RESULTS

13 patients had 18F-FCH positive pulmonary and 8 patients malignant lesions: 5 patients (38%) had a primary lung cancer (2 squamous cell carcinomas, 1 papillary adenocarcinoma, 1 typical pulmonary carcinoid, 1 bronchioloalveolar carcinoma) and 3 patients (23%) PCa metastases. Benign lesions were found in 5 subjects (38%). SUVmax and maximum diameter were neither significantly different in primary and metastatic tumors nor between malignant and benign lesions.

CONCLUSIONS

Although our results suggest that incidental uptake in the lungs in PCa patients are nonspecific, their detection may have a significant impact on patient management knowing that more than 60% represent malignant disease.

New acquisition protocol of 18F-choline PET/CT in prostate cancer patients: review of the literature about methodology and proposal of standardization

Purpose. (1) To evaluate a new acquisition protocol of ¹⁸F-choline (FCH) PET/CT for prostate cancer patients (PC), (2) to review acquisition ¹⁸F-choline PET/CT methodology, and (3) to propose a standardized acquisition protocol on FCH PET/CT in PC patients. Materials. 100 consecutive PC patients (mean age 70.5 years, mean PSA 21.35 ng/mL) were prospectively evaluated. New protocol consisted of an early scan of the pelvis immediately after the injection of the tracer (1 bed position of 4 min) followed by a whole body scan at one 1 hour. Early and 1 hour images were compared for interfering activity and pathologic findings. Results. The overall detection rate of FCH PET/CT was 64%. The early static images of the pelvis showed absence of radioactive urine in ureters, bladder, or urethra which allowed a clean evaluation of the prostatic fossae. Uptake in the prostatic region was better visualized in the early phase in 26% (7/30) of cases. Other pelvic pathologic findings (bone and lymph nodes) were visualized in both early and late images. Conclusion. Early ¹⁸F-choline images improve visualization of abnormal uptake in prostate fossae. All pathologic pelvic deposits (prostate, lymph nodes, and bone) were visualized in both early and late images.

Potential of hybrid ¹⁸F-fluorocholine PET/MRI for prostate cancer imaging

PURPOSE

To report the first results of hybrid (18)F-fluorocholine PET/MRI imaging for the detection of prostate cancer.

METHODS

This analysis included 26 consecutive patients scheduled for prostate PET/MRI before radical prostatectomy. The examinations were performed on a hybrid whole-body PET/MRI scanner. The MR acquisitions which included T2-weighted, diffusion-weighted and dynamic contrast-enhanced sequences were followed during the same session by whole-body PET scans. Parametric maps were constructed to measure normalized T2-weighted intensity (nT2), apparent diffusion coefficient (ADC), volume transfer constant (K (trans)), extravascular extracellular volume fraction (v e) and standardized uptake values (SUV). With pathology as the gold standard, ROC curves were calculated using logistic regression for each parameter and for the best combination with and without PET to obtain a MR model versus a PETMR model.

RESULTS

Of the 26 patients initially selected, 3 were excluded due to absence of an endorectal coil (2 patients) or prosthesis artefacts (1 patient). In the whole prostate, the area under the curve (AUC) for SUVmax, ADC, nT2, K (trans) and v e were 0.762, 0.756, 0.685, 0.611 and 0.529 with a best threshold at 3.044 for SUVmax and 1.075 × 10(-3) mm(2)/s for ADC. The anatomical distinction between the transition zone and the peripheral zone showed the potential of the adjunctive use of PET. In the peripheral zone, the AUC of 0.893 for the PETMR model was significantly greater (p = 0.0402) than the AUC of 0.84 for the MR model only. In the whole prostate, no relevant correlation was observed between ADC and SUVmax. The SUVmax was not affected by the Gleason score.

CONCLUSION

The performance of a hybrid whole-body (18)F-fluorocholine PET/MRI scan in the same session combined with a prostatic MR examination did not interfere with the diagnostic accuracy of the MR sequences. The registration of the PET data and the T2 anatomical MR sequence data allowed precise localization of hypermetabolic foci in the prostate. While in the transition zone the adenomatous hyperplasia interfered with cancer detection by PET, the quantitative analysis tool performed well for cancer detection in the peripheral zone.

Comparison of PET/CT and PET/MRI hybrid systems using a 68Ga-labelled PSMA ligand for the diagnosis of recurrent prostate cancer: initial experience

PURPOSE

(68)Ga-labelled HBED-CC-PSMA is a highly promising tracer for imaging recurrent prostate cancer (PCa). The intention of this study was to evaluate the feasibility of PET/MRI with this tracer.

METHODS

Twenty patients underwent PET/CT 1 h after injection of the (68)Ga-PSMA ligand followed by PET/MRI 3 h after injection. Data from the two investigations were first analysed separately and then compared with respect to tumour detection rate and radiotracer uptake in various tissues. To evaluate the quantification accuracy of the PET/MRI system, differences in SUVs between PET/CT and corresponding PET/MRI were compared with differences in SUVs between PET/CT 1 h and 3 h after injection in another patient cohort. This cohort was investigated using the same PET/CT system.

RESULTS

With PET/MRI, different diagnostic sequences, higher contrast of lesions and higher resolution of MRI enabled a subjectively easier evaluation of the images. In addition, four unclear findings on PET/CT could be clarified as characteristic of PCa metastases by PET/MRI. However, in PET images of the PET/MRI, a reduced signal was observed at the level of the kidneys (in 11 patients) and around the urinary bladder (in 15 patients). This led to reduced SUVs in six lesions. SUVmean values provided by the PET/MRI system were different in muscles, blood pool, liver and spleen.

CONCLUSION

PCa was detected more easily and more accurately with Ga-PSMA PET/MRI than with PET/CT and with lower radiation exposure. Consequently, this new technique could clarify unclear findings on PET/CT. However, scatter correction was challenging when the specific (68)Ga-PSMA ligand was used. Moreover, direct comparison of SUVs from PET/CT and PET/MR needs to be conducted carefully.

Androgen deprivation and high-dose radiotherapy for oligometastatic prostate cancer patients with less than five regional and/or distant metastases

BACKGROUND

Substantial survival may be observed with oligometastatic prostate cancer. Combining androgen deprivation (AD) and high-dose external beam radiotherapy (RT) to isolated regional or distant lesions may be proposed for these patients and the outcome of this strategy is the purpose of the present report.

MATERIAL AND METHODS

From 2003 to 2010, 50 prostate cancer patients were diagnosed with synchronous (n = 7) or metachronous (n = 43) oligometastases (OM). Among the relapsing patients, the recurrence occurred after radical prostatectomy in 33 patients and curative RT (± AD) in 10 patients. The median age at diagnosis was 63 years (range, 48-82). All patients underwent a bone scan and 18F-choline or 11C-acetate PET-CT at the time of diagnosis or relapse, showing regional and/or distant nodal and bone and/or visceral metastases in 33 and 17 patients, respectively. The median delivered effective dose was 64 Gy. All but one patient received neo-adjuvant and concomitant AD.

RESULTS

After a median follow-up of 31 months (range, 9-89) the three-year biochemical relapse-free survival (bRFS), clinical failure-free survival, and overall survival rates were 54.5%, 58.6% and 92%, respectively. No grade 3 toxicity was observed. Improved bRFS was found to be significantly associated with the number of OM. The three-year bRFS was 66.5% versus 36.4% for patients with 1 and > 1 OMs (p = 0.031). A normalised total dose (NTD in 2 Gy/fraction, alpha/beta = 2 Gy) above 64 Gy was also correlated with a better three-year bRFS compared to lower doses: 65% vs. 41.8%, respectively (p = 0.005). On multivariate analysis, only the NTD > 64 Gy retained statistical significance (HR: 0.37, 95% CI 0.15-0.93).

CONCLUSION

Oligometastatic patients may be successfully treated with short AD and high-dose irradiation to the metastatic lesions. High dose improves bRFS. Such a treatment strategy may hypothetically succeed to prolong the failure-free interval between two consecutive AD courses.

First imaging results of an intraindividual comparison of (11)C-acetate and (18)F-fluorocholine PET/CT in patients with prostate cancer at early biochemical first or second relapse after prostatectomy or radiotherapy

PURPOSE

(18)F-Fluorocholine (FCH) and (11)C-acetate (ACE) PET are widely used for detection of recurrent prostate cancer (PC). We present the first results of a comparative, prospective PET/CT study of both tracers evaluated in the same patients presenting with recurrence and low PSA to compare the diagnostic information provided by the two tracers.

METHODS

The study group comprised 23 patients studied for a rising PSA level after radical prostatectomy (RP, 7 patients, PSA ≤ 3 ng/ml), curative radiotherapy (RT, 7 patients, PSA ≤ 5 ng/ml) or RP and salvage RT (9 patients, PSA ≤ 5 ng/ml). Both FCH and ACE PET/CT scans were performed in a random sequence a median of 4 days (range 0 to 11 days) apart. FCH PET/CT was started at injection (307 ± 16 MBq) with a 10-min dynamic acquisition of the prostate bed, followed by a whole-body PET scan and late (45 min) imaging of the pelvis. ACE PET/CT was performed as a double whole-body PET scan starting 5 and 22 min after injection (994 ± 72 MBq), and a late view (45 min) of the prostate bed. PET/CT scans were blindly reviewed by two independent pairs of two experienced nuclear medicine physicians, discordant subgroup results being discussed to reach a consensus for positive, negative end equivocal results.

RESULTS

PET results were concordant in 88 out of 92 local, regional and distant findings (Cohen's kappa 0.929). In particular, results were concordant in all patients concerning local status, bone metastases and distant findings. Lymph-node results were concordant in 19 patients and different in 4 patients. On a per-patient basis results were concordant in 22 of 23 patients (14 positive, 5 negative and 3 equivocal). In only one patient was ACE PET/CT positive for nodal metastases while FCH PET/CT was overall negative; interestingly, the ACE-positive and FCH-negative lymph nodes became positive in a second FCH PET/CT scan performed a few months later.

CONCLUSION

Overall, ACE and FCH PET/CT showed excellent concordance, on both a per-lesion and a per-patient basis, suggesting that both tracers perform equally for recurrent prostate cancer staging.

Comparison of PET imaging with a (68)Ga-labelled PSMA ligand and (18)F-choline-based PET/CT for the diagnosis of recurrent prostate cancer

PURPOSE

Positron emission tomography (PET) with choline tracers has found widespread use for the diagnosis of prostate cancer (PC). However, choline metabolism is not increased in a considerable number of cases, whereas prostate-specific membrane antigen (PSMA) is overexpressed in most PCs. Therefore, a (68)Ga-labelled PSMA ligand could be superior to choline tracers by obtaining a high contrast. The aim of this study was to compare such a novel tracer with standard choline-based PET/CT.

METHODS

Thirty-seven patients with biochemical relapse of PC [mean prostate-specific antigen (PSA) 11.1 ± 24.1 ng/ml, range 0.01-116] were retrospectively analysed after (18)F-fluoromethylcholine and (68)Ga-PSMA PET/CT within a time window of 30 days. Radiotracer uptake that was visually considered as PC was semi-quantitatively analysed by measuring the maximum standardized uptake values (SUVmax) of the scans acquired 1 h after injection of (68)Ga-PSMA complex solution (median 132 MBq, range 59-263 MBq) and (18)F-fluoromethylcholine (median 237 MBq, range 114-374 MBq), respectively. In addition, tumour to background ratios were calculated.

RESULTS

A total of 78 lesions characteristic for PC were detected in 32 patients using (68)Ga-PSMA PET/CT and 56 lesions were detected in 26 patients using choline PET/CT. The higher detection rate in (68)Ga-PSMA PET/CT was statistically significant (p=0.04). In five patients no lesion was found with both methods. All lesions detected by (18)F-fluoromethylcholine PET/CT were also seen by (68)Ga-PSMA PET/CT. In (68)Ga-PSMA PET/CT SUVmax was clearly (>10 %) higher in 62 of 78 lesions (79.1 %) and the tumour to background ratio was clearly (>10 %) higher in 74 of 78 lesions (94.9 %) when compared to (18)F-fluoromethylcholine PET/CT.

CONCLUSION

(68)Ga-PSMA PET/CT can detect lesions characteristic for PC with improved contrast when compared to standard (18)F-fluoromethylcholine PET/CT, especially at low PSA levels.

Choline PET or PET/CT and biochemical relapse of prostate cancer: a systematic review and meta-analysis

AIM

The increase of prostate-specific antigen (PSA) after radical retropubic prostatectomy (RP) or external beam radiotherapy (EBRT) is the most sensitive tool for detecting prostate cancer (PCa) recurrence, although this measure cannot distinguish between local, regional, or distant recurrence. The aim of this meta-analysis was to evaluate the diagnostic performance of 18F-choline and 11C-choline PET or PET/CT in detection of locoregional or distant metastases in PCa.

MATERIALS AND METHODS

Medline, Web of Knowledge, and Google Scholar search was carried out in order to select English-language articles dealing with diagnostic performance of both 18F-choline and 11C-choline PET for the detection of PCa recurrence after RP or EBRT. Articles were included only if absolute numbers of true-positive, true-negative, false-positive, and false-negative test results were available or derivable from the text and regarded local, lymph node, and distant metastases. Reviews, clinical reports, and editorial articles were excluded. All complete studies were re-analyzed thus performing a quantitative analysis.

RESULTS

From the years 2000 to 2012, we found 53 complete articles that critically evaluated the role of choline PET in restaging patients with PCa recurrence. The meta-analysis was carried out and dealt with 19 selected studies (12 studies for all sites of disease, 3 for lymph node metastases, and 4 for local recurrence), with a total of 1555 patients. The meta-analysis provided a pooled sensitivity of 85.6% (95% CI: 82.9%-88.1%) and pooled specificity of 92.6% (95% CI: 90.1%-94.6%) for all sites of disease (prostatic fossa, lymph nodes, and bone), a pooled sensitivity of 75.4% (95% CI: 66.9%-82.6%) and pooled specificity of 82% (95% CI: 68.6%-91.4%) for prostatic fossa recurrence, and a pooled sensitivity of 100% (95% CI: 90.5%-100%) and pooled specificity of 81.8% (95% CI: 48.2%-97.7%) for lymph node metastases. The heterogeneity ranged between 0.00% and 88.6%. The diagnostic odds ratios were 62.123 (95% CI: 24.783-155.72), 5.869 (95% CI: 1.818-18.946), and 138.57 (95% CI: 11.27-1703.8), respectively, for all sites of disease, local recurrence, and lymph node disease.

CONCLUSIONS

Choline PET and PET/CT represent high sensitivity and specificity techniques for the detection of locoregional and distant metastases in PCa patients with recurrence of disease. Moreover, a high diagnostic odds ratio was found for the identification of lymph node disease in patients with biochemical recurrence of PCa.

Comparison of integrated whole-body [11C]choline PET/MR with PET/CT in patients with prostate cancer

PURPOSE

To evaluate the performance of conventional [(11)C]choline PET/CT in comparison to that of simultaneous whole-body PET/MR.

METHODS

The study population comprised 32 patients with prostate cancer who underwent a single-injection dual-imaging protocol with PET/CT and subsequent PET/MR. PET/CT scans were performed applying standard clinical protocols (5 min after injection of 793 ± 69 MBq [(11)C]choline, 3 min per bed position, intravenous contrast agent). Subsequently (52 ± 15 min after injection) PET/MR was performed (4 min per bed position). PET images were reconstructed iteratively (OSEM 3D), scatter and attenuation correction of emission data and regional allocation of [(11)C]choline foci were performed using CT data for PET/CT and segmented Dixon MR, T1 and T2 sequences for PET/MR. Image quality of the respective PET scans and PET alignment with the respective morphological imaging modality were compared using a four point scale (0-3). Furthermore, number, location and conspicuity of the detected lesions were evaluated. SUVs for suspicious lesions, lung, liver, spleen, vertebral bone and muscle were compared.

RESULTS

Overall 80 lesions were scored visually in 29 of the 32 patients. There was no significant difference between the two PET scans concerning number or conspicuity of the detected lesions (p not significant). PET/MR with T1 and T2 sequences performed better than PET/CT in anatomical allocation of lesions (2.87 ± 0.3 vs. 2.72 ± 0.5; p = 0.005). The quality of PET/CT images (2.97 ± 0.2) was better than that of the respective PET scan of the PET/MR (2.69 ± 0.5; p = 0.007). Overall the maximum and mean lesional SUVs exhibited high correlations between PET/CT and PET/MR (ρ = 0.87 and ρ = 0.86, respectively; both p < 0.001).

CONCLUSION

Despite a substantially later imaging time-point, the performance of simultaneous PET/MR was comparable to that of PET/CT in detecting lesions with increased [(11)C]choline uptake in patients with prostate cancer. Anatomical allocation of lesions was better with simultaneous PET/MR than with PET/CT, especially in the bone and pelvis. These promising findings suggest that [(11)C]choline PET/MR might have a diagnostic benefit compared to PET/CT in patients with prostate cancer, and now needs to be further evaluated in prospective trials.

Target volume definition in high-risk prostate cancer patients using sentinel node SPECT/CT and 18 F-choline PET/CT

BACKGROUND

To assess the influence of sentinel lymph nodes (SNs) SPECT/CT and 18 F-choline (18 F-FCH) PET/CT in radiotherapy (RT) treatment planning for prostate cancer patients with a high-risk for lymph node (LN) involvement.

METHODS

Twenty high-risk prostate cancer patients underwent a pelvic SPECT acquisition following a transrectal ultrasound guided injection of 99mTc-Nanocoll into the prostate. In all patients but one an 18 F-FCH PET/CT for RT treatment planning was performed. SPECT studies were coregistered with the respective abdominal CTs. Pelvic SNs localized on SPECT/CT and LN metastases detected by 18 F-FCH PET/CT were compared to standard pelvic clinical target volumes (CTV).

RESULTS

A total of 104 pelvic SNs were identified on SPECT/CT (mean 5.2 SNs/patient; range 1-10). Twenty-seven SNs were located outside the standard pelvic CTV, 17 in the proximal common iliac and retroperitoneal regions above S1, 9 in the pararectal fat and 1 in the inguinal region. SPECT/CT succeeded to optimize the definition of the CTV and treatment plans in 6/20 patients due to the presence of pararectal SNs located outside the standard treatment volume. 18 F-FCH PET/CT identified abnormal tracer uptake in the iliac LN region in 2/19 patients. These abnormal LNs were negative on SPECT/CT suggesting a potential blockade of lymphatic drainage by metastatic LNs with a high tumour burden.

CONCLUSIONS

Multimodality imaging which combines SPECT/CT prostate lymphoscintigraphy and 18 F-FCH PET/CT identified SNs outside standard pelvic CTVs or highly suspicious pelvic LNs in 40% of high-risk prostate cancer patients, highlighting the potential impact of this approach in RT treatment planning.

Detection of recurrent prostate cancer with 18F-fluorocholine PET/CT in relation to PSA level at the time of imaging

Purpose

To evaluate fluorine-18 fluorocholine (FCH) PET/CT for the detection of recurrent prostate cancer in relation to prostate-specific antigen (PSA) level.

Methods

FCH PET/CT was performed in 50 patients with rising PSA levels at follow-up of primary treatment of prostate cancer (radical prostatectomy in 28, radiation therapy in 13, and brachytherapy in 9). PET detection rates were determined at various PSA thresholds and examined by receiver operating characteristic analysis.

Results

Findings consistent with recurrent prostate cancer were noted on FCH PET/CT in 31/50 (62 %) patients, with positive findings in 17/18 (94 %), and 11/13 (85 %), 2/7 (29 %), and 1/12 (8 %) patients with PSA >4, >2–4, >0.5–2, and ≤0.5 ng/mL, respectively. These findings were indicative of local/regional recurrence in 23 cases and systemic recurrence in 8 cases, with only a single route of recurrence (i.e., either hematogenous, lymphatic, or intraprostatic) in 84 % of PET scans with positive findings. Abnormal tumor activity was detected in 88 % of patients with a PSA level of 1.1 ng/mL or higher, and in only 6 % of patients with a PSA level below this threshold value.

Conclusion

FCH PET/CT may serve to identify the route of tumor progression in patients with recurrent prostate cancer; however, the likelihood of tumor detection may be related to the PSA level at the time of imaging.

Imaging of prostate cancer with PET/CT and radioactively labeled choline derivates

PET- and PET/CT using [(11)C]- and [(18)F]-labeled choline derivates are increasingly being used for imaging of prostate cancer. The value of PET- and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in biochemical recurrence of prostate cancer has been examined in many studies and demonstrates an increasing importance. PET/CT, in comparison to PET, improves especially the lesion localization as well as characterization. Primary prostate cancer can be detected with moderate sensitivity using PET and PET/CT using [(11)C]- and [(18)F]-labeled choline derivates--the differentiation between benign prostatic hyperplasia, prostatitis, or high-grade intraepithelial neoplasia (HGPIN) is not always possible. At the present time, [(11)C]-choline PET/CT is not recommended in the primary setting but may be utilized in clinically suspected prostate cancer with repeatedly negative prostate biopsies, in preparation of a focused re-biopsy. Promising results have been obtained for the use of PET and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in patients with biochemical recurrence. The detection rate of choline PET and PET/CT for local, regional, and distant recurrence in patients with a biochemical recurrence shows a linear correlation with PSA value at the time of imaging and reaches about 75% in patients with PSA > 3 ng/ml. Even at PSA values below 1 ng/ml, the recurrence can be diagnosed with choline PET/CT in approximately one-third of the patients. PET and PET/CT with [(11)C]- and [(18)F]-choline derivates can be helpful in the clinical setting for choosing a therapeutic strategy in the sense of an individualized treatment: an early diagnosis of recurrence is crucial to the choice of optimal treatment. Especially important for the choice of treatment is the exact localization of the site of recurrence: local recurrence, recurrence as lymph node metastasis, or systemic recurrence, as it has direct influence on individual therapy. This article reviews the use of PET and PET/CT with [(11)C]- and [(18)F]-labeled choline derivates in prostate cancer imaging with special emphasis on patients with biochemical recurrence. We briefly provide an overview of PET tracers for prostate cancer imaging, the rationale of using choline derivatives for prostate cancer imaging and discuss the contribution of choline PET/CT in patients suffering from prostate cancer with an emphasis on recurrent disease. Furthermore, we provide an outlook on future prospects of choline PET/CT imaging for therapy guidance and monitoring in the framework of therapy individualization.

Role of (18)F-choline PET/CT in evaluation of patients with prostate carcinoma

Background

Choline presents a high affinity for malignant prostate tissue. It can be labelled with positron emitting ¹⁸F, and used for the evaluation of patients with prostate carcinoma by PET/CT imaging. The aim of this paper is to summarise our experience with fluoromethylcholine (¹⁸F-choline) PET/CT in patients with prostate cancer.

Methods

In 4 months we investigated the patients with histopathological (or cytological) confirmed prostate cancer. Two observers evaluated the early and late ¹⁸F-choline PET images in correlation with corresponding localising CT images and using the semiquantitative standard uptake value (SUV) calculation.

Results

The ¹⁸F-choline PET/CT was made in 50 patients with prostate cancer. There were 18 patients after radical prostatectomy and 32 without surgery. In all patients without surgery the pathological uptake was seen in the prostate. In 14 (44 %) patients of this group there was evidence of metastatic spread in local or distant lymph nodes and/or bones. In out of 18 patients after radical prostatectomy the local recurrence was detected in 6 patients (33%) and distant metastases were present in 2 patients (10%).

Conclusions

¹⁸F-choline PET/CT seems to be useful imaging modality in patients with prostate carcinoma; it can demonstrate spread of the disease preoperatively and detect the local recurrence after radical prostatectomy.

18F-fluorocholine PET-guided target volume delineation techniques for partial prostate re-irradiation in local recurrent prostate cancer

BACKGROUND AND PURPOSE

We evaluate the contribution of (18)F-choline PET/CT in the delineation of gross tumour volume (GTV) in local recurrent prostate cancer after initial irradiation using various PET image segmentation techniques.

MATERIALS AND METHODS

Seventeen patients with local-only recurrent prostate cancer (median=5.7 years) after initial irradiation were included in the study. Rebiopsies were performed in 10 patients that confirmed the local recurrence. Following injection of 300 MBq of (18)F-fluorocholine, dynamic PET frames (3 min each) were reconstructed from the list-mode acquisition. Five PET image segmentation techniques were used to delineate the (18)F-choline-based GTVs. These included manual delineation of contours (GTV(man)) by two teams consisting of a radiation oncologist and a nuclear medicine physician each, a fixed threshold of 40% and 50% of the maximum signal intensity (GTV(40%) and GTV(50%)), signal-to-background ratio-based adaptive thresholding (GTV(SBR)), and a region growing (GTV(RG)) algorithm. Geographic mismatches between the GTVs were also assessed using overlap analysis.

RESULTS

Inter-observer variability for manual delineation of GTVs was high but not statistically significant (p=0.459). In addition, the volumes and shapes of GTVs delineated using semi-automated techniques were significantly higher than those of GTVs defined manually.

CONCLUSIONS

Semi-automated segmentation techniques for (18)F-choline PET-guided GTV delineation resulted in substantially higher GTVs compared to manual delineation and might replace the latter for determination of recurrent prostate cancer for partial prostate re-irradiation. The selection of the most appropriate segmentation algorithm still needs to be determined.

RapidArc, intensity modulated photon and proton techniques for recurrent prostate cancer in previously irradiated patients: a treatment planning comparison study

Background

A study was performed comparing volumetric modulated arcs (RA) and intensity modulation (with photons, IMRT, or protons, IMPT) radiation therapy (RT) for patients with recurrent prostate cancer after RT.

Methods

Plans for RA, IMRT and IMPT were optimized for 7 patients. Prescribed dose was 56 Gy in 14 fractions. The recurrent gross tumor volume (GTV) was defined on ¹⁸F-fluorocholine PET/CT scans. Plans aimed to cover at least 95% of the planning target volume with a dose > 50.4 Gy. A maximum dose (D_Max) of 61.6 Gy was allowed to 5% of the GTV. For the urethra, D_Max was constrained to 37 Gy. Rectal D_Median was < 17 Gy. Results were analyzed using Dose-Volume Histogram and conformity index (CI₉₀) parameters.

Results

Tumor coverage (GTV and PTV) was improved with RA (V_95% 92.6 ± 7.9 and 83.7 ± 3.3%), when compared to IMRT (V_95% 88.6 ± 10.8 and 77.2 ± 2.2%). The corresponding values for IMPT were intermediate for the GTV (V_95% 88.9 ± 10.5%) and better for the PTV (V_95%85.6 ± 5.0%). The percentages of rectal and urethral volumes receiving intermediate doses (35 Gy) were significantly decreased with RA (5.1 ± 3.0 and 38.0 ± 25.3%) and IMPT (3.9 ± 2.7 and 25.1 ± 21.1%), when compared to IMRT (9.8 ± 5.3 and 60.7 ± 41.7%). CI₉₀ was 1.3 ± 0.1 for photons and 1.6 ± 0.2 for protons. Integral Dose was 1.1 ± 0.5 Gy*cm³ *10⁵ for IMPT and about a factor three higher for all photon's techniques.

Conclusion

RA and IMPT showed improvements in conformal avoidance relative to fixed beam IMRT for 7 patients with recurrent prostate cancer. IMPT showed further sparing of organs at risk.

Molecular PET/CT imaging-guided radiation therapy treatment planning

The role of positron emission tomography (PET) during the past decade has evolved rapidly from that of a pure research tool to a methodology of enormous clinical potential. (18)F-fluorodeoxyglucose (FDG)-PET is currently the most widely used probe in the diagnosis, staging, assessment of tumor response to treatment, and radiation therapy planning because metabolic changes generally precede the more conventionally measured parameter of change in tumor size. Data accumulated rapidly during the last decade, thus validating the efficacy of FDG imaging and many other tracers in a wide variety of malignant tumors with sensitivities and specificities often in the high 90 percentile range. As a result, PET/computed tomography (CT) had a significant impact on the management of patients because it obviated the need for further evaluation, guided further diagnostic procedures, and assisted in planning therapy for a considerable number of patients. On the other hand, the progress in radiation therapy technology has been enormous during the last two decades, now offering the possibility to plan highly conformal radiation dose distributions through the use of sophisticated beam targeting techniques such as intensity-modulated radiation therapy (IMRT) using tomotherapy, volumetric modulated arc therapy, and many other promising technologies for sculpted three-dimensional (3D) dose distribution. The foundation of molecular imaging-guided radiation therapy lies in the use of advanced imaging technology for improved definition of tumor target volumes, thus relating the absorbed dose information to image-based patient representations. This review documents technological advancements in the field concentrating on the conceptual role of molecular PET/CT imaging in radiation therapy treatment planning and related image processing issues with special emphasis on segmentation of medical images for the purpose of defining target volumes. There is still much more work to be done and many of the techniques reviewed are themselves not yet widely implemented in clinical settings.