The Impact of Positron Emission Tomography with 18F-Fluciclovine on the Treatment of Biochemical Recurrence of Prostate Cancer: Results from the LOCATE Trial

A bicentric retrospective analysis of clinical utility of 18F-fluciclovine PET in biochemically recurrent prostate cancer following primary radiation therapy: is it helpful in patients with a PSA rise less than the Phoenix criteria?

PURPOSE

¹⁸F-Fluciclovine PET imaging has been increasingly used in the restaging of prostate cancer patients with biochemical recurrence (BCR); however, its clinical utility in patients with low prostate-specific antigen (PSA) levels following primary radiation therapy has not been well-studied. This study aims to determine the detection rate and diagnostic accuracy of ¹⁸F-fluciclovine PET and the patterns of prostate cancer recurrence in patients with rising PSA after initial radiation therapy, particularly in patients with PSA levels below the accepted Phoenix definition of BCR (PSA nadir +2 ng/mL).

METHODS

This retrospective study included patients from two tertiary institutions who underwent ¹⁸F-fluciclovine PET scans for elevated PSA level following initial external beam radiation therapy, brachytherapy, and/or proton therapy. Logistic regression and receiver operating characteristic (ROC) curve analyses were performed to determine the diagnostic accuracy of ¹⁸F-fluciclovine PET and associations of PSA kinetic parameters with ¹⁸F-fluciclovine PET outcome.

RESULTS

One hundred patients were included in this study. The overall detection rate on a patient-level was 79% (79/100). ¹⁸F-Fluciclovine PET was positive in 62% (23/37) of cases with PSA below the Phoenix criteria. The positive predictive value of ¹⁸F-fluciclovine PET was 89% (95% CI: 80-94%). In patients with PSA below the Phoenix criteria, the PSA velocity had the highest predictive value of ¹⁸F-fluciclovine PET outcome. PSA doubling time (PSADT) and PSA velocity were associated with the presence of extra-pelvic metastatic disease.

CONCLUSION

¹⁸F-Fluciclovine PET can identify recurrent disease at low PSA level and PSA rise below accepted Phoenix criteria in patients with suspected BCR after primary radiation therapy, particularly in patients with low PSADT or high PSA velocity. In patients with low PSADT or high PSA velocity, there is an increased probability of extra-pelvic metastases. Therefore, these patients are more likely to benefit from PET/CT or PET/MRI than pelvic MRI alone.

18F-fluciclovine-PET/CT imaging versus conventional imaging alone to guide postprostatectomy salvage radiotherapy for prostate cancer (EMPIRE-1): a single centre, open-label, phase 2/3 randomised controlled trial

BACKGROUND

Molecular imaging is increasingly used to guide treatment decisions and planning in prostate cancer. We aimed to evaluate the role of ¹⁸F-fluciclovine-PET/CT in improving cancer control compared with conventional imaging (bone scan and either CT or MRI) alone for salvage postprostatectomy radiotherapy.

METHODS

In EMPIRE-1, a single-centre, open-label, phase 2/3 randomised controlled trial, patients with prostate cancer with detectable PSA after prostatectomy and negative conventional imaging (no extrapelvic or bone findings) were randomly assigned in a 1:1 ratio to radiotherapy directed by conventional imaging alone or to conventional imaging plus ¹⁸F-fluciclovine-PET/CT. Computer-generated randomisation was stratified by PSA concentration, adverse pathology indicators, and androgen deprivation therapy intent. In the ¹⁸F-fluciclovine-PET/CT group, radiotherapy decisions were rigidly determined by PET findings, which were also used for target delineation. The primary endpoint was 3 year event-free survival, with events defined as biochemical or clinical recurrence or progression, or initiation of systemic therapy, using univariate and multivariable analyses in patients who received radiotherapy. This trial is registered with ClinicalTrials.gov, NCT01666808 and is closed to new participants.

FINDINGS

From Sept 18, 2012, to March 4, 2019, 165 patients were randomly assigned, with median follow-up of 3·52 years (95% CI 2·98-3·95). PET findings resulted in four patients in the ¹⁸F-fluciclovine-PET/CT group having radiotherapy aborted; these patients were excluded from survival analyses. Median survival was not reached (95% CI 35·2-not reached; 33% of 81 patients had events) in the conventional imaging group compared with not reached (95% CI not reached-not reached; 20% of 76 patients) in the ¹⁸F-fluciclovine-PET/CT group, and 3 year event-free survival was 63·0% (95% CI 49·2-74·0) in the conventional imaging group versus 75·5% (95% CI 62·5-84·6) for ¹⁸F-fluciclovine-PET/CT (difference 12·5; 95% CI 4·3-20·8; p=0·0028). In adjusted analyses, study group (hazard ratio 2·04 [95% CI 1·06-3·93], p=0·0327) was significantly associated with event-free survival. Toxicity was similar in both study groups, with the most common adverse events being late urinary frequency or urgency (37 [46%] of 81 patients in the conventional imaging group and 31 [41%] of 76 in the PET group), and acute diarrhoea (11 [14%] in the conventional imaging group and 16 [21%] in the PET group).

INTERPRETATION

Inclusion of ¹⁸F-fluciclovine-PET into postprostatectomy radiotherapy decision making and planning significantly improved survival free from biochemical recurrence or persistence. Integration of novel PET radiotracers into radiotherapy decisions and planning for prostate cancer patients warrants further study.

FUNDING

National Institutes of Health/National Cancer Institute, Blue Earth Diagnostics, and Winship Cancer Institute of Emory University.

Current State of Personalized Genitourinary Cancer Radiotherapy in the Era of Precision Medicine

Radiation therapy plays a crucial role for the management of genitourinary malignancies, with technological advancements that have led to improvements in outcomes and decrease in treatment toxicities. However, better risk-stratification and identification of patients for appropriate treatments is necessary. Recent advancements in imaging and novel genomic techniques can provide additional individualized tumor and patient information to further inform and guide treatment decisions for genitourinary cancer patients. In addition, the development and use of targeted molecular therapies based on tumor biology can result in individualized treatment recommendations. In this review, we discuss the advances in precision oncology techniques along with current applications for personalized genitourinary cancer management. We also highlight the opportunities and challenges when applying precision medicine principles to the field of radiation oncology. The identification, development and validation of biomarkers has the potential to personalize radiation therapy for genitourinary malignancies so that we may improve treatment outcomes, decrease radiation-specific toxicities, and lead to better long-term quality of life for GU cancer survivors.

Diagnostic performance of 18F-fluciclovine PET/CT in prostate cancer patients with rising PSA level ≤ 0.5 ng/ml after multiple treatment failures

This retrospective study is to assess the performance of ¹⁸F-Fluciclovine PET/CT in prostate cancer (PC) patients with multiple treatment failures and prostate-specific antigen (PSA) ≤ 0.5 ng/mL. PC patients with multiple treatment failures who had PSA level within 2-week interval of ¹⁸F-Fluciclovine PET/CT (PSA_PET) ≤ 0.5 ng/mL were identified in retrospective review of our institution's database (n=28). Patient, tumor, treatment, PSA and castration characteristics as well as findings on ¹⁸F-Fluciclovine PET/CT were collected and compared between positive and negative ¹⁸F-Fluciclovine PET/CT subgroups by using Fisher's exact test. The overall detection rate of ¹⁸F-Fluciclovine PET/CT was 7 of 28 studies (25%). PSA_PET > 0.2 ng/mL was associated with higher detection rates in all (33.3 vs 10%, P=0.172), castration-resistant (CR) (50 vs 20%, P=0.343) and castration-sensitive (CS) (28.6 vs 0%, P=0.179) patients. Sites of recurrence were local 42.9% (3/7), nodal 42.9% (3/7) and bone metastases 14.3% (1/7). Higher Gleason score (GS 8-10) (33.3 vs 14.5%, P=0.396), advanced tumor stage (T3-T4) (35.7 vs 20%, P=0.653), second-line androgen deprivation therapy (ADT) uses (66.7 vs 20%, P=0.145), chemotherapy uses (50 vs 23.1%, P=0.444) and CRPC (33.3 vs 21.1%, P=0.483) related to positivity of ¹⁸F-Fluciclovine PET/CT but none reached statistical significance. Performance of ¹⁸F-Fluciclovine PET/CT in prostate cancer patients with multiple treatment failures and PSA_PET ≤ 0.5 ng/mL was acceptable particularly in patients with PSA_PET ≥ 0.3 ng/mL, CRPC, initial GS ≥ 8 or T3-T4.

Prostate Cancer Liver Metastases Presenting as Relatively Photopenic Lesions on 18F-Fluciclovine PET/CT

ABSTRACT

A 66-year-old man with prostate adenocarcinoma status post radical retropubic prostatectomy and bilateral pelvic lymph node dissection, followed by salvage external beam radiation therapy to the prostate bed 1 year after surgery. Over the course of 17 years, the patient underwent multiple lines of systemic treatment for recurrent disease. He was referred for restaging 18F-fluciclovine PET/CT due to rising serum prostate-specific antigen levels. Contrast-enhanced 18F-fluciclovine PET/CT images demonstrated multiple new liver metastases, which were relatively photopenic in comparison with the physiologic radiotracer activity in the surrounding normal liver parenchyma.

Current and Emerging Clinical Applications of PSMA PET Diagnostic Imaging for Prostate Cancer

Prostate-specific membrane antigen (PSMA) is highly expressed on most prostate cancer (PCa) cells, and several PSMA ligands for PET imaging are now available worldwide. ⁶⁸Ga-PSMA-11 has already received U.S. Food and Drug Administration and European Medicines Agency approval, and use of PSMA PET is currently suggested by several international guidelines for investigating PCa in different clinical settings. In primary PCa, PSMA PET has been shown to be superior to cross-sectional imaging for the detection of pelvic lymph nodes and distant metastases with subsequent clinical management changes. Additionally, it might also have a role in intraprostatic tumor localization, especially when combined with multiparametric MRI. In a setting of PCa recurrence, higher detection rates have been observed than for any other available imaging techniques, especially at low prostate-specific antigen values. Furthermore, PSMA PET consistently led to a shift in clinical management, thus increasing the proportion of radiotherapy, surgery, or other focal therapies at the expense of systemic options or no treatment. In oligometastatic disease after radical surgery, PSMA PET may be relevant in guiding a metastasis-directed therapy approach, as preliminary data seem to suggest a benefit in terms of progression-free survival after treatment of PSMA PET-positive lesions. As a staging and gatekeeping technique, PSMA PET represents a reliable whole-body imaging procedure in combination with second-line therapy of castration-resistant PCa, as well as being pivotal when assessing patients eligible for radioligand therapy such as ¹⁷⁷Lu-PSMA. This critical review aims at providing a comprehensive overview of the latest literature on the current or emerging main indications, as well as a general outlook on the recommended interpretation criteria for PSMA PET imaging.

18F-Fluciclovine PET/CT in Therapeutic Decision Making for Prostate Cancer: A Large Single-Center Practice-Based Analysis

METHODS

We carried out a retrospective cohort study of patients with BR after primary treatment of PC who received imaging with 18F-fluciclovine PET/CT at our institution between January 2010 and January 2019. PET/CT results were compared with biopsy, conventional imaging results, and/or response to PC therapy. 18F-Fluciclovine PET/CT performance statistics and effects on treatment planning were calculated.

RESULTS

A total of 328 patients with a median age of 71 years (range, 47-90 years) and median serum prostate-specific antigen level of 1.6 ng/mL (0.02-186.7 ng/mL) were included. Three hundred thirty-six 18F-fluciclovine PET/CT scans were analyzed and classified as positive (65%), negative (25%), or equivocal (10%) based on radiology reports. Sensitivity was 93% (95% confidence interval, 86%-96%) and specificity was 63% (95% confidence interval, 45%-77%). Of patients with known management recommendations post-PET/CT, scan results changed or influenced pre-PET/CT management plans in 73%, and 58% of recommendations involved treatment modality decisions. Overall, 82% of patients' actual management was concordant with post-PET/CT recommendations. Of evaluable patients, 116 (35%) had some form of post-PET radiotherapy included in their care plans, with 95% receiving radiotherapy at a PET-avid target.

CONCLUSIONS

In the largest single-institutional cohort to date, 18F-fluciclovine PET/CT showed value in the workup of PC in the setting of BR, with noteworthy influence over clinical management decisions. Further studies are needed to evaluate whether PET/CT-based changes in management are associated with improved outcomes.

Role of 18F-Fluciclovine and Prostate-Specific Membrane Antigen PET/CT in Guiding Management of Oligometastatic Prostate Cancer: AJR Expert Panel Narrative Review

Twenty-five years ago, oligometastatic disease was proposed as an intermediary clinical state of cancer with unique implications for therapies that may impact cancer evolution and patient outcome. Identification of limited metastases that are potentially amenable to targeted therapies fundamentally depends on the sensitivity of diagnostic tools, including new-generation imaging methods. For men with biochemical recurrence after definitive therapy of the primary prostate cancer, PET/CT using either the FDA-approved radiolabeled amino acid analogue ¹⁸F-fluciclovine or investigational radiolabeled agents targeting prostate-specific membrane antigen (PSMA) enables identification of early metastases at lower serum PSA levels than was previously feasible using conventional imaging. Evidence supports PSMA PET/CT as the most sensitive imaging modality available for identifying disease sites in oligometastatic prostate cancer. PSMA PET/CT will likely become the modality of choice after regulatory approval and will drive the development of trials of emerging metastasis-directed therapies such as stereotactic ablative body radiation and radioguided surgery. Indeed, numerous ongoing or planned clinical trials are studying advances in management of oligometastatic prostate cancer based on this heightened diagnostic capacity. In this rapidly evolving clinical environment, radiologists and nuclear medicine physicians will play major roles in facilitating clinical decision making and management of patients with oligometastatic prostate cancer.

Incidental Detection of Urothelial Carcinoma on 18F-Fluciclovine PET/CT

ABSTRACT

18F-Fluciclovine PET/CT has become a common diagnostic imaging study used in the evaluation of biochemical recurrence in prostate cancer since its approval in 2016. We present a case report of an 82-year-old man with history of both prostate and bladder cancer who presented for a fluciclovine study due to rising PSA levels. There was incidental detection of focal penile activity, and a subsequent urethral biopsy performed showed urothelial carcinoma, which was also seen on a subsequent MRI study.

Patterns of Recurrence, Detection Rates, and Impact of 18-F Fluciclovine PET/CT on the Management of Men With Recurrent Prostate Cancer

OBJECTIVE

To evaluate the characteristics of FACBC PET/CT in detecting recurrent prostate cancer after radiation or prostatectomy. The secondary aim was to determine the impact of FACBC PET/CT on radiation treatment recommendations in men with biochemical recurrence postprostatectomy.

METHODS

This is a single center retrospective study of men who underwent an FACBC PET/CT for rising PSA after definitive prostate cancer therapy. Detection rates in men with recurrence following any definitive treatment were compared at different PSA levels and anatomical sites. Radiotherapy treatment recommendations for patients postprostatectomy based on conventional imaging findings were compared to recommendations based on FACBC PET/CT findings.

RESULTS

A total of 103 men underwent imaging with FACBC PET/CT. 74.8% (77) had lesions consistent with sites of prostate cancer recurrence. At PSA thresholds of <1, 1-2, and >2 ng/mL lesions were detected in 35.5%, 63.6%, and 95.2% of patients respectively (P <.001). The most common site of recurrence was outside of the pelvis (37). Detection of extraprostatic or extrapelvic recurrence was observed in 45.5% of men in the PSA tertile <1ng/mL. FACBC PET/CT results led to changes to the recommended radiotherapy treatment plan in 44.1% (15/34) of men with recurrence following radical prostatectomy.

CONCLUSION

FACBC PET/CT demonstrated increased detection of recurrent prostate cancer with increasing PSA levels. Most recurrences were found outside the pelvis. Results of FACBC PET/CT changed radiotherapy management decisions in men treated with prostatectomy, supporting its use in localizing sites of disease recurrence in men with prostate cancer.

The Clinical Utility of 18F-Fluciclovine PET/CT in Biochemically Recurrent Prostate Cancer: an Academic Center Experience Post FDA Approval

PURPOSE

To evaluate the diagnostic performance and clinical utility of ¹⁸F-fluciclovine PET/CT in patients with biochemical recurrence (BCR) of prostate cancer (PC).

METHODS

¹⁸F-Fluciclovine scans of 165 consecutive men with BCR after primary definitive treatment with prostatectomy (n = 102) or radiotherapy (n = 63) were retrospectively evaluated. Seventy patients had concurrent imaging with at least one other conventional modality (CT (n = 31), MRI (n = 31), or bone scan (n = 26)). Findings from ¹⁸F-fluciclovine PET were compared with those from conventional imaging modalities. The positivity rate and impact of ¹⁸F-fluciclovine PET on patient management were recorded. In 33 patients who underwent at least one other PET imaging (¹⁸F-NaF PET/CT (n = 12), ⁶⁸Ga-PSMA11 PET/CT (n = 5), ¹⁸F-DCFPyL PET/CT (n = 20), and ⁶⁸Ga-RM2 PET/MRI (n = 5)), additional findings were evaluated.

RESULTS

The overall positivity rate of ¹⁸F-fluciclovine PET was 67 %, which, as expected, increased with higher prostate-specific antigen (PSA) levels (ng/ml): 15 % (PSA < 0.5), 50 % (0.5 ≤ PSA < 1), 56 % (1 ≤ PSA < 2), 68 % (2 ≤ PSA < 5), and 94 % (PSA ≥ 5), respectively. One hundred and two patients (62 %) had changes in clinical management based on ¹⁸F-fluciclovine PET findings. Twelve of these patients (12 %) had lesion localization on ¹⁸F-fluciclovine PET, despite negative conventional imaging. Treatment plans of 14 patients with negative ¹⁸F-fluciclovine PET were changed based on additional PET imaging with a different radiopharmaceutical.

CONCLUSION

¹⁸F-Fluciclovine PET/CT remains a useful diagnostic tool in the workup of patients with BCR PC, changing clinical management in 62 % of participants in our cohort.

Evaluating determinants of receipt of molecular imaging in biochemical recurrent prostate cancer

BACKGROUND

Molecular imaging with novel radiotracers is changing the treatment landscape in prostate cancer (PCa). Currently, standard of care includes either conventional and molecular imaging at time of biochemical recurrence (BCR). This study evaluated the determinants of and cost associated with utilization of molecular imaging for BCR PCa.

METHODS

This is a retrospective observational cohort study among men with BCR PCa from June 2018 to May 2019. Multivariate logistic regression models were employed to analyze the primary outcome: receipt of molecular imaging (e.g. Fluciclovine PET and Prostate Specific Membrane Antigen PET) as part of diagnostic work-up for BCR PCa. Multivariate linear regression models were used to analyze the secondary outcome: overall healthcare cost within a 1-year time frame.

RESULTS

The study sample included 234 patients; 79.1% White, 2.1% Black, 8.5% Asian/Pacific Islander, and 10.3% Other. The majority were 55 years or older (97.9%) and publicly insured (74.8%). Analysis indicated a one-unit reduction in PSA is associated with 1.3 times higher likelihood of receiving molecular imaging (p < 0.01). Analysis found that privately insured patients were associated with approximately $500,000 more in hospital reimbursement (p < 0.01) as compared to the publicly insured. Additionally, a one-unit increase in PSA is associated with $6254 increase in hospital reimbursement or an increase in total payments by 2.1% (p < 0.05).

CONCLUSIONS

Higher PSA was associated with lower likelihood for molecular imaging and higher cost in a one-year time frame. Higher cost was also associated with private insurance, but there was no clear relationship between insurance type and imaging type.

Recent updates and developments in PET imaging of prostate cancer

A number of positron emission tomography (PET) radiotracers have been developed to improve the sensitivity and specificity of imaging for prostate cancer. These radiotracers include the bone-seeking agent Na¹⁸F as well as more tumor-specific compounds such as ¹¹C-choline and ¹⁸F-fluciclovine. In this review, we will discuss the advantages and disadvantages of these PET radiotracers for the imaging of men with prostate cancer across a range of clinical contexts. We will also touch upon radiotracers in late clinical development that have not gained regulatory approval, including those targeted against prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR).

Prostate cancer recurrence in patients with negative or equivocal conventional imaging: A role for 18F-fluciclovine-PET/CT in delineating sites of recurrence and identifying patients with oligometastatic disease

INTRODUCTION

Despite improvements in overall survival, biochemical recurrence of prostate cancer, characterized by rising prostate-specific antigen (PSA) levels after curative intent primary therapy, remains common. With the advent of highly sensitive molecular imaging, men with limited metastatic disease burden, or oligometastatic prostate cancer, are increasingly being identified. The LOCATE trial (NCT02680041) assessed the impact of positron emission tomography (PET) with ¹⁸F-fluciclovine on management of men with prostate cancer recurrence after curative intent primary therapy and negative/equivocal conventional imaging. Here, we use LOCATE data to characterize the sites of disease recurrence and explore the potential for ¹⁸F-fluciclovine-PET/CT to evaluate oligometastatic disease.

METHODS

Eligible men (≥18 years; prior curative intent treatment of prostate cancer; recurrence based on rising PSA; negative/equivocal conventional imaging) underwent ¹⁸F-fluciclovine-PET/CT according to standard protocols. The primary outcome measure of the LOCATE trial was a revised management plan post-scan. We performed a secondary analysis of the LOCATE imaging data to characterize anatomical sites of disease recurrence and to explore the potential for ¹⁸F-fluciclovine-PET/CT to evaluate oligometastatic disease. Imaging results were stratified by baseline PSA levels and prior treatment(s) and the Fisher exact test used to analyze differences between groups. Oligometastatic disease was defined as 1-5 extraprostatic lesions (≤3 lesions in any single organ system) plus negative prostate/bed imaging (as a surrogate for primary tumor control).

RESULTS

Of 213 enrolled patients, 164 (77%) had undergone prostatectomy as their initial treatment; their median PSA was 0.57ng/ml. For the 49 patients with an intact prostate, the median PSA was 5.5ng/ml. The overall ¹⁸F-fluciclovine-PET/CT detection rate was 57%. Detection rates were 84% in men with intact prostates and 49% in those who had undergone prostatectomy, with the difference being attributable to prostate/bed findings (71% vs. 18%, respectively). The detection rate in lymph nodes was 29% and in bone was 11%. In total, 53/213 (25%) had oligometastatic disease. Twenty (38%) oligometastatic patients had PSA ≤1.0 ng/ml. Forty-two (79%) experienced a change to their management plan following the scan, commonly to target a lesion identified by ¹⁸F-fluciclovine-PET/CT. The majority of management changes (74%) involved a new treatment modality; however, 10 patients (24%) experienced a modification of the existing plan for radiotherapy to incorporate a boost to an area guided by the ¹⁸F-fluciclovine-PET/CT results.

CONCLUSION

Even at low PSA levels, ¹⁸F-fluciclovine-PET/CT identified a diverse pattern of recurrence missed with conventional imaging. One-quarter of men had oligometastatic disease, raising the potential for ¹⁸F-fluciclovine-PET/CT to guide targeted treatment of oligometastases.

Salvage Therapies After 18F-Fluciclovine Detected Prostate Cancer Recurrences

BACKGROUND

F-Fluciclovine is the most recent prostate cancer (PCa)-directed PET radiotracer approved by the US Food and Drug Administration for detection of recurrent PCa. We report the treatments and outcomes of patients at our institution with PCa recurrences detected on F-fluciclovine PET/CT.

METHODS

We identified men with recurrent PCa detected on F-fluciclovine PET/CT performed between 2017 and 2018 who were previously treated definitively and analyzed their patterns of care and cancer-specific outcomes.

RESULTS

We identified 28 men with recurrent PCa detected on F-fluciclovine PET/CT. Twenty-three were initially treated with surgery and 13 also received postoperative radiation therapy (RT). Five patients were initially treated with definitive radiation. After surgery, the median time to F-fluciclovine PET/CT was 67 months (median prostate-specific antigen [PSA] of 1.63 ng/mL). After RT, the median time to F-fluciclovine PET/CT was 95 months with median PSA of 13.31 ng/mL. Six men recurred locally, 9 recurred in the pelvic nodes, 9 had distant nodal recurrences, and 4 had osseous metastases. Of the patients initially treated with surgery, 4 received salvage radiation and 3 received androgen deprivation therapy (ADT). Of the patients initially treated with surgery and postoperative RT, 3 received salvage pelvic nodal dissection, 4 received salvage radiation, and 2 received ADT. Of the patients initially treated with radiation, 4 received salvage ADT. All had PSA decline after salvage therapy.

CONCLUSIONS

F-fluciclovine PET/CT can localize PCa recurrences, and subsequent salvage therapies appear effective with decreasing PSA. Longer follow-up will reveal if these diagnostic tests and subsequent therapies will improve PCa survival.

Hypofractionated Postoperative Radiotherapy for Prostate Cancer: Is the Field Ready Yet?

Context

Radiotherapy (RT) is a valid adjuvant treatment for men with high-risk pathological features after radical prostatectomy and a salvage treatment for biochemical recurrence. A major inconvenience is that RT takes course over 7–8 wk in these settings, which has been shown to limit its use. Retrospective and pilot prospective investigations suggest that hypofractionation may provide noninferior outcomes but report variable results regarding toxicities. Additionally, our evolving understanding of prostate cancer radiobiology suggests that hypofractionated regimens may not increase toxicity.

Objective

We examine and review the rationale and clinical evidence of hypofractionated RT in the adjuvant and salvage settings for prostate cancer.

Evidence acquisition

We reviewed relevant literature, with a particular focus on recent studies employing hypofractionated RT.

Evidence synthesis

Hypofractionated RT in the adjuvant or salvage setting is not a standard option for prostate cancer RT outside of an investigational trial. While smaller studies show conflicting data regarding toxicity, initial evidence from larger clinical trials appears to demonstrate that hypofractionated postoperative RT is as effective and safe as conventionally fractionated courses.

Conclusions

With the growing acceptance of hypofractionation across other cancer sites and the rise of extreme hypofractionation for definitive prostate cancer treatment, hypofractionated postoperative therapy for prostate cancer is poised to become an option, as it may reduce the burden on men and treatment centers while maintaining clinical efficacy and safety. Prospective trials are currently ongoing to address efficacy and safety concerns.

Patient summary

Postoperative radiotherapy is a potentially curative treatment for patients with high-risk disease or recurrence after surgery. Shortening of the treatment regimen with the availability of modern treatment delivery techniques in conjunction with the integration of molecular imaging information to refine treatment volumes may improve therapeutic benefit without increasing toxicity.

Comparison of Diagnostic Utility of Fluciclovine PET/CT Versus Pelvic Multiparametric MRI for Prostate Cancer in the Pelvis in the Setting of Rising PSA After Initial Treatment

PURPOSE

The aim of this study was to investigate the imaging diagnostic performance of F-fluciclovine PET/CT and pelvic multiparametric MRI (mpMRI) for prostate cancer in the setting of rising PSA after initial treatment, with a focus on detection of recurrent and metastatic prostate cancer in the pelvis.

METHODS

Patients with prostate cancer who had fluciclovine PET and pelvic mpMRI between October 2017 and October 2018 in our center were retrospectively reviewed. Patients were included if they had fluciclovine PET/CT and mpMRI within a 3-month interval. Patients were excluded if they had separate concurrent cancer or if the PSA were more than 2-fold difference with an absolute difference more than 1 ng/mL between the 2 image studies. For each eligible patient, we compared all abnormal lesions identified on either scan. The findings were verified by pathology or other imaging techniques within minimal 10-month clinical follow-up.

RESULTS

A total of 129 patients with 129 paired tests were included in this study. Fluciclovine PET/CT and pelvic MRI had a high degree of concordance (121/129, 93.8%). The sensitivity, specificity, positive predictive value, and negative predictive value for fluciclovine PET/CT and mpMRI were 96.6%, 94.3%, 93.4%, and 97%, and 91.5%, 95.7%, 94.7%, and 93%, respectively. There were no statistical significant differences in diagnostic performance between the 2 imaging tests. Among the 8/129 discordant cases, although fluciclovine PET/CT provided definitive diagnosis when mpMRI was equivocal due to paramagnetic artifacts from fiducial markers and detected normal-sized regional lymph nodes, mpMRI detected subcentimeter periurethral recurrence and clarified physiological urinary artifacts that was not appreciated on fluciclovine PET/CT.

CONCLUSIONS

Our single-center study demonstrated that fluciclovine PET/CT has similar diagnostic performance with pelvic mpMRI in detecting recurrent/metastatic prostate disease in the pelvis in the setting of rising PSA after initial treatment. Moreover, fluciclovine PET/CT and mpMRI have different implications in different clinical scenario; each test has its own limitation and pitfalls, but can be complementary to each other.

Diagnostic performance of F-18 fluciclovine PET/CT in post-radical prostatectomy prostate cancer patients with rising prostate-specific antigen level ≤0.5 ng/mL

PURPOSE

The aim of the study was to assess the diagnostic performance of fluciclovine positron emission tomography (PET)/computerized tomography (CT) in post-radical prostatectomy prostate cancer patients with rising prostate-specific antigen (PSA) ≤0.5 ng/mL, and identify the associated predictive factors of positive studies.

PATIENTS AND METHODS

From 30 June 2017 to 9 August 2019, patients with post-radical prostatectomy prostate cancer who underwent F-18 fluciclovine PET/CT and had PSA level within 2-week interval (PSAPET) ≤0.5 ng/mL were enrolled into this single-institution retrospective study. Data on tumor characteristics, including Gleason scores, extra-prostatic extension, seminal vesicle invasion, surgical margin and nodal metastasis, PSA after radical prostatectomy, previous hormonal therapy, PSA doubling time (PSADT), scanner type, PSAPET and site of recurrence were collected. Comparison of these factors between groups of positive and negative fluciclovine PET/CT was done by using Mann-Whitney U-test and Fisher's exact test.

RESULTS

Of 94 eligible patients with post-radical prostatectomy prostate cancer, 10 patients had positive studies (10.6%). Detection rate at PSAPET 0.1, 0.2, 0.3, 0.4 and 0.5 ng/mL were 0% (0/11), 0% (0/15), 20% (6/30), 4% (1/25) and 23.1% (3/13), respectively. Upon multivariate analysis of clinical factors, only a PSADT <3 months (P = 0.023) was shown to have a statistically significant correlation with a positive study.

CONCLUSION

In post-radical prostatectomy prostate cancer patients with rising PSA 0.1-0.5 ng/mL, the sensitivity of F-18 fluciclovine PET/CT for identifying tumor recurrence/metastases is poor with an overall detection rate of 10.6%. Larger prospective studies are required to validate these findings.

The Role of PET-CT Imaging in Prostate Cancer

Prostate cancer is the commonest malignancy to affect men in the United Kingdom. Extraprostatic disease detection at staging and in the setting of biochemical recurrence is essential in determining treatment strategy. Conventional imaging including computed tomography and bone scintigraphy are limited in their ability to detect sites of loco-regional nodal and metastatic bone disease, particularly at clinically relevant low prostate-specific antigen levels. The use of positron emission tomography-computed tomography has helped overcome these deficiencies and is leading a paradigm shift in the management of prostate cancer using a wide range of radiopharmaceuticals. Their mechanisms of action, utility in both staging and biochemical recurrence, and comparative strengths and weaknesses will be covered in this article.

Clinical application of Fluciclovine PET, choline PET and gastrin-releasing polypeptide receptor (bombesin) targeting PET in prostate cancer

PURPOSE OF REVIEW

The aim of this review is to explore the clinical application of different PET radiopharmaceuticals in prostate cancer (PCa), beyond inhibitors of the prostate-specific membrane antigen (PSMA).

RECENT FINDINGS

Choline PET represented in the last decades the standard of reference for PET imaging in PCa and has been recently included in clinical trials evaluating the efficacy of metastasis-directed therapy in oligo-metastatic disease. Fluciclovine, as synthetic amino acid, has been proposed for investigating PCa. The results obtained by the first prospective studies led to FDA approval in 2016 in patients with biochemical recurrence. Recently, phase II/III trials explored its accuracy compared with PSMA PET and its impact on patient management. Imaging the gastrin-releasing polypeptide receptor (GRPR) recently drawn attention. Radio-labelled GRPR antagonists have the potential to be used as theranostic agents. Further evaluation is needed to understand the relation between GRPR expression and hormonal-resistant PCa, and for tumors characterized by heterogeneity of receptors expressed (e.g. PSMA-negative) on their cell surface.

SUMMARY

Other new generation PET tracers may play an important role in PCa, namely in case of PSMA-negative phenotypes.

Novel PET imaging methods for prostate cancer

INTRODUCTION

Prostate cancer is a common neoplasm but conventional imaging methods such as CT and bone scan are often insensitive. A new class of PET agents have emerged to diagnose and manage prostate cancer.

METHODS

The relevant literature on PET imaging agents for prostate cancer was reviewed.

RESULTS

This review shows a broad range of PET imaging agents, the most successful of which is prostate specific membrane antigen (PSMA) PET. Other agents either lack the sensitivity or specificity of PSMA PET.

CONCLUSION

Among the available PET agents for prostate cancer, PSMA PET has emerged as the leader. It is likely to have great impact on the diagnosis, staging and management of prostate cancer patients.

Molecular imaging of prostate cancer: Review of imaging agents, modalities, and current status

INTRODUCTION

The clinical course of Prostate cancer (PCa) are markedly diverse, ranging from indolent to highly aggressive disseminated disease. Molecular imaging techniques are playing an increasing role in early PCa detection, staging and disease recurrence. There are some molecular imaging modalities, radiotracers agents and its performance are important in current clinical practice PCa.

OBJECTIVE

This review summarizes the latest information regarding molecular imaging of PCa and is designed to assist urologists with ordering and interpreting these modalities and different radiotracers for different patients.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted up to September 2019. We selected the most recent and relevant original articles, metanalysis and reviews that have provided relevant information to guide molecular imaging modalities and radiotracers use.

EVIDENCE SYNTHESIS

In this review, we discuss 3 main molecular imaging modalities and 7 radiotracer technologies available.

CONCLUSIONS

The use molecular imaging modalities and radiotracers has a unique role in biochemical recurrence and diagnosis of ganglionar and bone progression of PCa. In the present time, no one of these molecular imaging modalities can be recommended over the classical work-up of abdominopelvic CT scan and bone scan, and large-scale and multi-institutional studies are required to validate the efficacy and cost utility of these new technologies.

Fluorine-18-Labeled Fluciclovine PET/CT in Primary and Biochemical Recurrent Prostate Cancer Management

OBJECTIVE. The purpose of this article is to review the utility of ¹⁸F-fluciclovine PET/CT in the evaluation of recurrent prostate cancer. CONCLUSION. Fluorine-18-labeled fluciclovine PET/CT has shown promise in the evaluation of recurrent prostate cancer. Its performance has been superior to that of other imaging modalities. It has had good diagnostic accuracy, especially in the detection of extra-prostatic disease recurrence, and the findings have an impact on treatment planning. Gallium-68-labeled prostate-specific membrane antigen PET/CT has also had excellent performance in the detection of biochemically recurrent prostate cancer with detection rates superior to those of fluciclovine PET/CT.

Effect of 18F-Fluciclovine Positron Emission Tomography on the Management of Patients With Recurrence of Prostate Cancer: Results From the FALCON Trial

PURPOSE

Early and accurate localization of lesions in patients with biochemical recurrence (BCR) of prostate cancer may guide salvage therapy decisions. The present study, 18F-Fluciclovine PET/CT in biochemicAL reCurrence Of Prostate caNcer (FALCON; NCT02578940), aimed to evaluate the effect of 18F-fluciclovine on management of men with BCR of prostate cancer.

METHODS AND MATERIALS

Men with a first episode of BCR after curative-intent primary therapy were enrolled at 6 UK sites. Patients underwent 18F-fluciclovine positron emission tomography/computed tomography (PET/CT) according to standardized procedures. Clinicians documented management plans before and after scanning, recording changes to treatment modality as major and changes within a modality as other. The primary outcome measure was record of a revised management plan postscan. Secondary endpoints were evaluation of optimal prostate specific antigen (PSA) threshold for detection, salvage treatment outcome assessment based on 18F-fluciclovine-involvement, and safety.

RESULTS

18F-Fluciclovine was well tolerated in the 104 scanned patients (median PSA = 0.79 ng/mL). Lesions were detected in 58 out of 104 (56%) patients. Detection was broadly proportional to PSA level; ≤1 ng/mL, 1 out of 3 of scans were positive, and 93% scans were positive at PSA >2.0 ng/mL. Sixty-six (64%) patients had a postscan management change (80% after a positive result). Major changes (43 out of 66; 65%) were salvage or systemic therapy to watchful waiting (16 out of 66; 24%); salvage therapy to systemic therapy (16 out of 66; 24%); and alternative changes to treatment modality (11 out of 66, 17%). The remaining 23 out of 66 (35%) management changes were modifications of the prescan plan: most (22 out of 66; 33%) were adjustments to planned brachytherapy/radiation therapy to include a 18F-fluciclovine-guided boost. Where 18F-fluciclovine guided salvage therapy, the PSA response rate was higher than when 18F-fluciclovine was not involved (15 out of 17 [88%] vs 28 out of 39 [72%]).

CONCLUSIONS

18F-Fluciclovine PET/CT located recurrence in the majority of men with BCR, frequently resulting in major management plan changes. Incorporating 18F-fluciclovine PET/CT into treatment planning may optimize targeting of recurrence sites and avoid futile salvage therapy.

Recent developments in the treatment of non-metastatic castration resistant prostate cancer

Non-metastatic castration resistant prostate cancer (nmCRPC) is defined as a disease state withlack of radiographic evidence of metastatic disease, a confirmed rising PSA level on continuous ADT and maintaining a castrate level of testosterone following definitive therapy. Prior to the publication of PROSPER, SPARTAN and ARAMIS, no trials have demonstrated a clinical benefit for these patients. Recently enzalutamide, apalutamide, and darolutamide respectively, were tested in this disease setting with metastasis free survival (MFS) as the primary endpoint for each trial. In this review article, we define key terms related to the discussion of nmCRPC, examine the clinical trial design, and safety profile for each of these three key clinical trials and present updated overall survival (OS) results from these studies. Also we specifically discuss the key clinical trial results including the primary endpoint of MFS for each trial as well as quality of life effects of these three androgen receptor antagonists. Finally, this article examines the potential impact of molecular imaging testing on the applicability of these clinical trial results.

PSMA-targeted Radiotracers versus 18F Fluciclovine for the Detection of Prostate Cancer Biochemical Recurrence after Definitive Therapy: A Systematic Review and Meta-Analysis

Background National guidelines endorse fluorine 18 (¹⁸F) fluciclovine PET/CT for the detection of prostate cancer (PCa) in men with biochemically recurrent PCa. The comparative performance between fluciclovine and gallium 68 or ¹⁸F prostate-specific membrane antigen (PSMA) PET/CT, a newer examination, is unclear. Purpose To compare the detection of biochemical recurrence using fluciclovine versus PSMA-targeted radiotracers in patients with a prostate-specific antigen (PSA) level less than 2 ng/mL. Materials and Methods With use of the Preferred Reporting Items for a Systematic Review and Meta-Analysis of Diagnostic Test Accuracy, or PRISMA-DTA, guidelines, a systematic review of PubMed and EMBASE databases between 2012 and 2019 was performed. Studies of fluciclovine PET/CT or PSMA PET/CT in biochemical recurrence were identified. PSA levels, clinical data, and reference standards were obtained when available. A random-effects model was applied to pooled estimates and 95% confidence intervals (CIs) around the prevalence of a positive examination, stratified according to PSA tier. Results Quantitative analysis included 482 patients (median age, 67 years; interquartile range, 67-67 years) in six fluciclovine studies and 3217 patients (median age, 68 years; interquartile range, 67-70 years) in 38 PSMA studies. Pooled detection rates for PSMA and fluciclovine were 45% (95% CI: 38%, 52%) and 37% (95% CI: 25%, 49%), respectively, for a PSA level less than 0.5 ng/mL (P = .46); 59% (95% CI: 52%, 66%) and 48% (95% CI: 34%, 61%) for a PSA level of 0.5-0.9 ng/mL (P = .19); and 80% (95% CI: 75%, 85%) and 62% (95% CI: 54%, 70%) for a PSA level of 1.0-1.9 ng/mL (P = .01). A reference standard was positive in 703 of 735 patients (96%) in the PSMA cohort and 247of 256 (97%) in the fluciclovine cohort. Conclusion Patient-level detection rates for biochemically recurrent prostate cancer were greater for prostate-specific membrane antigen-targeted radiotracers than fluciclovine for prostate specific antigen levels of 1.0-1.9 ng/mL. © RSNA, 2020 Online supplemental material is available for this article.

Understanding and Improving 18F-Fluciclovine PET/CT Reports: A Guide for Physicians Treating Patients with Biochemical Recurrence of Prostate Cancer

The positron emission tomography (PET) tracer ¹⁸F-fluciclovine has seen increasing use to localize disease in men with biochemical recurrence of prostate cancer, i.e., elevated prostate-specific antigen (PSA) levels post-treatment. ¹⁸F-Fluciclovine PET/computed tomography (CT) imaging reports now play central roles in many physician-patient discussions. However, because no standardized grading system or templates yet exist for ¹⁸F-fluciclovine image assessment, reports vary in format, comprehensiveness, and terminology and may be challenging to fully understand. To better utilize these documents, referring physicians should be aware of six key features of ¹⁸F-fluciclovine PET/CT. First, ¹⁸F-fluciclovine is a radiolabeled synthetic amino acid targeting the amino acid transporters ASCT2 and LAT1, which are ubiquitous throughout the body, but overexpressed in prostate cancer. Second, ¹⁸F-fluciclovine image interpretation is predominantly visual/qualitative: radiotracer uptake in suspicious lesions is compared with uptake in bone marrow or blood pool. Location of ¹⁸F-fluciclovine-avid lesions relative to typical recurrence sites and findings elsewhere in the patient are considered when evaluating lesions' probability of malignancy, as is visibility on maximum intensity projection images when assessing bone lesions. Third, ¹⁸F-fluciclovine PET/CT detection rates increase as PSA levels rise. Fourth, detection rates may differ among centers, possibly due to equipment and reader experience. Fifth, since no diagnostic test is 100% accurate, scan data should not be used in isolation. Lastly, ¹⁸F-fluciclovine PET/CT findings frequently induce changes in disease management plans. In the prospective multicenter LOCATE and FALCON studies, scans altered management plans in 59% (126/213) and 64% (66/104) of patients, respectively; 78% (98/126) and 65% (43/66) of changes, respectively, involved modality switches. Referring physicians and imagers should collaborate to improve scan reports. Referrers should clearly convey critical information, including prescan PSA levels, and open clinical questions. Imagers should produce reports that read like consultations, avoid leaving open questions, and if needed, provide thoughts on next diagnostic steps.

Cost-consequence analysis of 18F-fluciclovine for the staging of recurrent prostate cancer

Background: Current detection methodologies are often unable to identify the location and extent of recurrent prostate cancer (PCa) leading potentially to 'futile' local therapies in the presence of metastatic disease. The use of ¹⁸ F-fluciclovine PET/CT may lead to better patient management. Objective: The aim of this study was to quantify the economic impact and cost-consequence of using ¹⁸ F-fluciclovine PET/CT in PCa recurrence. Study design: A decision analytic model based on recurrent PCa imaging guidelines. Setting: US hospital. Participants: PCa patients experiencing biochemical recurrence. Intervention: ¹⁸ F-fluciclovine PET/CT was compared to conventional imaging. Main outcome measure: Budget impact, correct diagnoses, futile treatments, and cost-consequence (cost per correct diagnosis) Results: For a hypothetical hospital serving 500,000 individuals, the model showed the use of ¹⁸ F-fluciclovine reduced 'futile' therapies by 19.2%. Re-imaging costs were reduced by 40.2% ($8.2 million); however, when assuming diagnostic and staging costs only, the total costs increased from $31.2 to $34.6 million (10.9%), driven by ¹⁸ F-fluciclovine imaging agent and procedure costs. The cost per 'correct' diagnosis declined $30,673 (46.8%). When including subsequent 5-year patient management, the cost per 'correct' diagnosis declined $410,206 (49.2%). Conclusion: ¹⁸ F-fluciclovine PET/CT imaging may improve the clinical management of men with recurrent PCa with minimal increase in healthcare spending.

Isolated Hepatic Metastasis of Prostate Cancer with Variable 18F-fluociclovine Uptake by PET/CT Imaging

A 74-year-old man presented with rapid rising prostate-specific antigen (PSA) 2 years after treatment of prostate cancer with prostatectomy and salvage radiation therapy. PSA increased from 923 to 4349 ng/mL within 2 months. No osseous metastatic lesions of prostate cancer were detected by ¹⁸F-sodium fluoride PET/CT imaging at an outside facility. ¹⁸F-fluciclovine PET/CT imaging was performed to evaluate local recurrence of prostate cancer at surgical bed of prostatectomy and distant metastasis. One small focus of low-level ¹⁸F-fluciclovine radiotracer uptake was noted in the surgical bed of prostatectomy without corresponding soft tissue mass on CT. No fluciclovine-avid lymph nodes or osseous metastatic lesions were detected, but multiple hypodense lesions of variable ¹⁸F-fluciclovine radiotracer uptake were noted in the liver, concerning for isolated liver metastasis of prostate cancer. The patient underwent docetaxel chemotherapy for treatment of prostate cancer liver metastasis and showed a favorable response to treatment by significant decreased size of the hypodense lesions in the liver on post treatment abdominal CT, along with dramatic reduction of PSA level and improvement of liver function. The findings from this case highlight the importance of checking hypoattenuating lesions in the liver for the presence of prostate cancer metastatic lesions that might appear similar to other benign hypoattenuating lesions of low fluciclovine uptake relative to physiological ¹⁸F-fluciclovine uptake in the normal liver tissues, a potential pitfall at interpretation of ¹⁸F-fluociclovine PET/CT imaging.

Extraprostatic Uptake of 18F-Fluciclovine: Differentiation of Nonprostatic Neoplasms From Metastatic Prostate Cancer

OBJECTIVE. Fluciclovine is a synthetic radiolabeled amino acid analog used for imaging of biochemical recurrent prostate cancer. Uptake of fluciclovine is mediated by several amino acid transporters, including alanine-serine-cysteine transporter 2 and large neutral amino acid transporters, which are known to be overexpressed in other malignancies. CONCLUSION. Knowledge of the common patterns of prostate cancer recurrence, in addition to what other neoplasms can show uptake, is critical for accurate study interpretation.

18F-rhPSMA-7 PET for the Detection of Biochemical Recurrence of Prostate Cancer After Radical Prostatectomy

¹⁸F-labeled prostate-specific membrane antigen (PSMA) PET tracers are increasingly used in preference to ⁶⁸Ga-PSMA-11 for restaging biochemical recurrence (BCR) of prostate cancer. They are associated with longer half-lives, larger-scale production, and lower positron range than their ⁶⁸Ga-labeled counterparts. Here, we describe the efficacy of an ¹⁸F-labeled radiohybrid PSMA, rhPSMA-7, a novel theranostic PSMA-targeting agent for imaging BCR of prostate cancer. Methods: Datasets from 261 consecutive patients with noncastrate BCR after radical prostatectomy who underwent ¹⁸F-rhPSMA-7 PET/CT at our institution between June 2017 and March 2018 were reviewed retrospectively. All lesions suspected of being recurrent prostate cancer were recorded. The detection rate for sites of presumed recurrence was correlated with patients' prostate-specific antigen (PSA) level, primary Gleason score, and prior therapy (androgen deprivation therapy and external-beam radiation therapy). Results: The 261 patients had a median PSA level of 0.96 ng/mL (range, 0.01-400 ng/mL). The median injected activity of ¹⁸F-rhPSMA-7 was 336 MBq, with a median uptake time of 76 min. In total, 211 patients (81%) showed pathologic findings on ¹⁸F-rhPSMA-7 PET/CT. The detection rates were 71% (42/59), 86% (44/51), 86% (42/49), and 95% (76/80) at PSA levels of 0.2 to <0.5 ng/mL, 0.5 to <1 ng/mL, 1 to <2 ng/mL, and ≥2 ng/mL, respectively. In 32% patients (7/22) with a PSA of less than 0.2 ng/mL, suggestive lesions were present. ¹⁸F-rhPSMA-7 PET/CT revealed local recurrence in 43% of patients (113). Lymph node metastases were present in the pelvis in 42% of patients (110), in the retroperitoneum in 17% (45), and in a supradiaphragmatic location in 8.0% (21). Bone and visceral metastases were detected in 21% (54) and 3.8% (10), respectively. Detection efficacy was not influenced by prior external-beam radiation therapy (79.1% vs. 82.1%, P = 0.55), androgen deprivation therapy within the 6 mo preceding imaging (80.6% vs. 80.9%, P = 0.54), or primary Gleason score (77.9% for ≤7 vs. 82.6% for ≥8, P = 0.38). Conclusion: ¹⁸F-rhPSMA-7 PET/CT offers high detection rates in early BCR after radical prostatectomy, especially among patients with low PSA values.

Prospective Evaluation of 18F-DCFPyL PET/CT in Biochemically Recurrent Prostate Cancer in an Academic Center: A Focus on Disease Localization and Changes in Management

¹⁸F-DCFPyL (2-(3-{1-carboxy-5-[(6-¹⁸F-fluoropyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid) is a promising PET radiopharmaceutical targeting prostate-specific membrane antigen (PSMA). We present our experience with this single-academic-center prospective study evaluating the positivity rate of ¹⁸F-DCFPyL PET/CT in patients with biochemical recurrence (BCR) of prostate cancer (PC). Methods: We prospectively enrolled 72 men (52-91 y old; mean ± SD, 71.5 ± 7.2) with BCR after primary definitive treatment with prostatectomy (n = 42) or radiotherapy (n = 30). The presence of lesions compatible with PC was evaluated by 2 independent readers. Fifty-nine patients had scans concurrent with at least one other conventional scan: bone scanning (24), CT (21), MR (20), ¹⁸F-fluciclovine PET/CT (18), or ¹⁸F-NaF PET (14). Findings from ¹⁸F-DCFPyL PET/CT were compared with those from other modalities. Impact on patient management based on ¹⁸F-DCFPyL PET/CT was recorded from clinical chart review. Results: ¹⁸F-DCFPyL PET/CT had an overall positivity rate of 85%, which increased with higher prostate-specific antigen (PSA) levels (ng/mL): 50% (PSA < 0.5), 69% (0.5 ≤ PSA < 1), 100% (1 ≤ PSA < 2), 91% (2 ≤ PSA < 5), and 96% (PSA ≥ 5). ¹⁸F-DCFPyL PET detected more lesions than conventional imaging. For anatomic imaging, 20 of 41 (49%) CT or MRI scans had findings congruent with ¹⁸F-DCFPyL, whereas ¹⁸F-DCFPyL PET was positive in 17 of 41 (41%) cases with negative CT or MRI findings. For bone imaging, 26 of 38 (68%) bone or ¹⁸F-NaF PET scans were congruent with ¹⁸F-DCFPyL PET, whereas ¹⁸F-DCFPyL PET localized bone lesions in 8 of 38 (21%) patients with negative results on bone or ¹⁸F-NaF PET scans. In 8 of 18 (44%) patients, ¹⁸F-fluciclovine PET had located the same lesions as did ¹⁸F-DCFPyL PET, whereas 5 of 18 (28%) patients with negative ¹⁸F-fluciclovine findings had positive ¹⁸F-DCFPyL PET findings and 1 of 18 (6%) patients with negative ¹⁸F-DCFPyL findings had uptake in the prostate bed on ¹⁸F-fluciclovine PET. In the remaining 4 of 18 (22%) patients, ¹⁸F-DCFPyL and ¹⁸F-fluciclovine scans showed different lesions. Lastly, 43 of 72 (60%) patients had treatment changes after ¹⁸F-DCFPyL PET and, most noticeably, 17 of these patients (24% total) had lesion localization only on ¹⁸F-DCFPyL PET, despite negative results on conventional imaging. Conclusion: ¹⁸F-DCFPyL PET/CT is a promising diagnostic tool in the work-up of biochemically recurrent PC, given the high positivity rate as compared with Food and Drug Administration-approved currently available imaging modalities and its impact on clinical management in 60% of patients.

18F-Facbc in Prostate Cancer: A Systematic Review and Meta-Analysis

Trans-1-amino-3-18F-fluorocyclobutanecarboxylic-acid (anti-[18F]-FACBC) has been approved for the detection of prostate cancer (PCa) in patients with elevated prostate-specific-antigen following prior treatment. This review and meta-analysis aimed to investigate the diagnostic performance of 18F-FACBC positron emission tomography/computed-tomography (PET/CT) in the detection of primary/recurrent PCa. A bibliographic search was performed including several databases, using the following terms: "FACBC"/"fluciclovine" AND "prostate cancer"/"prostate" AND "PET"/"Positron Emission Tomography". Fifteen and 9 studies were included in the systematic reviews and meta-analysis, respectively. At patient-based analysis, the pooled sensitivity and specificity of 18F-FACBC-PET/CT for the assessment of PCa were 86.3% and 75.9%, respectively. The pooled diagnostic odds-ratio value was 16.453, with heterogeneity of 30%. At the regional-based-analysis, the pooled sensitivity of 18F-FACBC-PET/CT for the evaluation of primary/recurrent disease in the prostatic bed was higher than in the extra-prostatic regions (90.4% vs. 76.5%, respectively); conversely, the pooled specificity was higher for the evaluation of extra-prostatic region than the prostatic bed (89% vs. 45%, respectively). 18F-FACBC-PET/CT seems to be promising in recurrent PCa, particularly for the evaluation of the prostatic bed. Additional studies to evaluate its utility in clinical routine are mandatory.

Multimodality Imaging of Prostate Cancer

Prostate cancer is a very heterogeneous disease, and contemporary management is focused on identification and treatment of the prognostically adverse high-risk tumors while minimizing overtreatment of indolent, low-risk tumors. In recent years, imaging has gained increasing importance in the detection, staging, posttreatment assessment, and detection of recurrence of prostate cancer. Several imaging modalities including conventional and functional methods are used in different clinical scenarios with their very own advantages and limitations. This continuing medical education article provides an overview of available imaging modalities currently in use for prostate cancer followed by a more specific section on the value of these different imaging modalities in distinct clinical scenarios, ranging from initial diagnosis to advanced, metastatic castration-resistant prostate cancer. In addition to established imaging indications, we will highlight some potential future applications of contemporary imaging modalities in prostate cancer.

18F-fluciclovine PET-CT and 68Ga-PSMA-11 PET-CT in patients with early biochemical recurrence after prostatectomy: a prospective, single-centre, single-arm, comparative imaging trial

BACKGROUND

National Comprehensive Cancer Network guidelines consider ¹⁸F-fluciclovine PET-CT for prostate cancer biochemical recurrence localisation after radical prostatectomy, whereas European Association of Urology guidelines recommend prostate-specific membrane antigen (PSMA) PET-CT. To the best of our knowledge, no prospective head-to-head comparison between these tests has been done so far. The aim of this study was to compare prospectively paired ¹⁸F-fluciclovine and PSMA PET-CT scans for localising biochemical recurrence of prostate cancer after radical prostatectomy in patients with low prostate-specific antigen (PSA) concentrations (<2·0 ng/mL).

METHODS

This was a prospective, single-centre, open-label, single-arm comparative study done at University of California Los Angeles (Los Angeles, CA, USA). Patients older than 18 years of age with prostate cancer biochemical recurrence after radical prostatectomy and PSA levels ranging from 0·2 to 2·0 ng/mL without any prior salvage therapy and with a Karnofsky performance status of at least 50 were eligible. Patients underwent ¹⁸F-fluciclovine (reference test) and PSMA (index test) PET-CT scans within 15 days. Detection rate of biochemical recurrence at the patient level and by anatomical region was the primary endpoint. A statistical power analysis demonstrated that a sample size of 50 patients was needed to show a 22% difference in detection rates in favour of PSMA (test for superiority). Each PET scan was interpreted by three independent masked readers and a consensus majority interpretation was generated (two vs one) to determine positive findings. This study is registered with ClinicalTrials.gov, number NCT02940262, and is complete.

FINDINGS

Between Feb 26, 2018, and Sept 20, 2018, 143 patients were screened for eligibility, of whom 50 patients were enrolled into the study. Median follow-up was 8 months (IQR 7-9). The primary endpoint was met; detection rates were significantly lower with ¹⁸F-fluciclovine PET-CT (13 [26%; 95% CI 15-40] of 50) than with PSMA PET-CT (28 [56%; 41-70] of 50), with an odds ratio (OR) of 4·8 (95% CI 1·6-19·2; p=0·0026) at the patient level; in the subanalysis of the pelvic nodes region (four [8%; 2-19] with ¹⁸F-fluciclovine vs 15 [30%; 18-45] with PSMA PET-CT; OR 12·0 [1·8-513·0], p=0·0034); and in the subanalysis of any extrapelvic lesions (none [0%; 0-6] vs eight [16%; 7-29]; OR non-estimable [95% CI non-estimable], p=0·0078).

INTERPRETATION

With higher detection rates, PSMA should be the PET tracer of choice when PET-CT imaging is considered for subsequent treatment management decisions in patients with prostate cancer and biochemical recurrence after radical prostatectomy and low PSA concentrations (≤2·0 ng/mL). Further research is needed to investigate whether higher detection rates translate into improved oncological outcomes.

FUNDING

None.

UK guidelines on 18F-fluciclovine PET/CT in prostate cancer imaging

The purpose of these guidelines is to assist specialists in Nuclear Medicine and Radionuclide Radiology in recommending, performing, interpreting and reporting F-fluciclovine PET/computed tomography. It should be recognised that adherence to the guidance in this document will not assure an accurate diagnosis or a successful outcome. These guidelines will assist individual departments in the formulation of their own local protocols. The guidelines apply to studies on adults. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources and the needs of the patient in order to deliver effective and safe medical care.

18F-Fluciclovine Parameters on Targeted Prostate Biopsy Associated with True Positivity in Recurrent Prostate Cancer

We evaluated ¹⁸F-fluciclovine uptake parameters that correlate with true positivity for local recurrence in non-prostatectomy-treated patients. Methods: Twenty-one patients (prostate-specific antigen level, 7.4 ± 6.8 ng/mL) with biochemical recurrence after nonprostatectomy local therapy (radiotherapy and cryotherapy) underwent dual-time-point ¹⁸F-fluciclovine (364.1 ± 37.7 MBq) PET/CT from pelvis to diaphragm. Prostatic uptake over background was delineated and coregistered to a prostate-biopsy-planning ultrasound. Transrectal biopsies of ¹⁸F-fluciclovine-defined targets were completed using a 3-dimensional visualization and navigation platform. Histologic analyses of lesions were completed. Lesion characteristics including SUV_max, target-to-background ratio (TBR), uptake pattern, and subjective reader's suspicion level were compared between true-positive (malignant) and false-positive (benign) lesions. Univariate analysis was used to determine the association between PET and histologic findings. Receiver-operating-characteristic curves were plotted to determine discriminatory cutoffs for TBR. Statistical significance was set at a P value of less than 0.05. Results: Fifty lesions were identified in 21 patients on PET. Seventeen of 50 (34.0%) targeted lesions in 10 of 21 patients were positive for malignancy. True-positive lesions had a significantly higher SUV_max (6.62 ± 1.70 vs. 4.92 ± 1.27), marrow TBR (2.57 ± 0.81 vs. 1.69 ± 0.51), and blood-pool TBR (4.10 ± 1.17 vs. 2.99 ± 1.01) than false-positive lesions at the early time point (P < 0.01) and remained significant at the delayed time point, except for blood-pool TBR. Focal uptake (odds ratio, 12.07; 95% confidence interval, 2.98-48.80; P < 0.01) and subjective highest suspicion level (odds ratio, 10.91; 95% confidence interval, 1.19-99.69; P = 0.03) correlated with true positivity. Using the receiver-operating-characteristic curve, optimal cutoffs for marrow TBR were 1.9 (area under the curve, 0.82) and 1.8 (area under the curve, 0.85) at early and delayed imaging, respectively. With these cutoffs, 15 of 17 malignant lesions were identified at both time points; however, fewer false-positive lesions were detected at the delayed time point (5/33) than at the early time point (11/33). Conclusion: True positivity of ¹⁸F-fluciclovine-targeted prostate biopsy in non-prostatectomy-treated patients correlates with focal uptake, TBR (blood pool and marrow), and subjective highest suspicion level. A marrow TBR of 1.9 at the early time point and 1.8 at the delayed time point had optimal discriminating capabilities. Despite the relatively low intraprostate positive predictive value (34.0%) with ¹⁸F-fluciclovine, application of these parameters to interpretative criteria may improve true positivity in the treated prostate.