Outcome after PSMA PET/CT based radiotherapy in patients with biochemical persistence or recurrence after radical prostatectomy

The Role of Prostate-specific Membrane Antigen Positron Emission Tomography for Assessment of Local Recurrence and Distant Metastases in Patients with Biochemical Recurrence of Prostate Cancer After Definitive Treatment: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

Positron emission tomography (PET) with prostate-specific membrane antigen (PSMA) radioligands has an established role in the assessment of recurrence of prostate cancer (PC) after primary treatment. However, an updated understanding of its diagnostic utility is warranted, particularly in the context of emerging targeted and systemic treatment options for recurrent PC. Our aim was to evaluate the diagnostic performance of PSMA PET for staging and detection of local or metastatic disease in patients with biochemical recurrence (BCR) following definitive treatment for PC.

METHODS

We conducted a systematic review (Web of Science/MEDLINE, Cochrane Library, and EMBASE from inception to April 25, 2024) and meta-analysis. Eligible retrospective and prospective studies had extractable data on PSMA PET for patients with BCR after radical prostatectomy (RP) or radiation therapy (RT). Risk of bias was assessed using the QUADAS-2 tool. Random-effects models were used to evaluate PSMA PET positivity rates across clinical subgroups stratified by PSA, primary treatment, PSMA PET radioligand, and anatomic lesion sites.

KEY FINDINGS AND LIMITATIONS

A total of 43 studies (8119 patients) were included. PSMA PET positivity rates varied substantially among patients with BCR after primary definitive treatment, with significant study heterogeneity (τ2 = 0.6; p < 0.001), which was mitigated in part after stratification by PSA category. Positivity rates were significantly higher after RT (92%) than after RP (60%; p < 0.001). PSMA PET positivity by anatomic location was 23% for local recurrence, 32% for pelvic nodes, 14% for extrapelvic nodes, 16% for bone metastases, and just 1% for visceral metastases. The positivity rate increased with PSA, from 48% at PSA 0.2-0.5 ng/ml to >90% at PSA >2 ng/ml. Gleason score (GS) at RP did not significantly influence the positivity rate (50% for GS ≤7 vs 62% for GS 8-10; p = 0.08). Heterogeneity limits the generalisability of our findings.

CONCLUSIONS AND CLINICAL IMPLICATIONS

We observed substantial variability in PSMA PET positivity rates in BCR because of significant study heterogeneity, mostly related to differences in treatment type, PSA, and anatomic sites. In post-RP BCR, approximately half of patients undergoing PSMA PET had positive findings, even at low PSA (0.2-0.5 ng/ml). In the post-RT setting, PSMA PET use was generally aligned with the Phoenix criterion for BCR, with most studies performing PSMA PET at PSA ≥2 ng/ml. Further research is needed to refine PSA thresholds for PSMA PET, particularly in the post-RT setting, and to assess its role in guiding salvage treatment decisions.

Long-term outcomes of PSMA PET/CT-guided radiotherapy in biochemical failure patients post-radical prostatectomy: a 5-year follow-up analysis

PURPOSE

To evaluate the role of PSMA PET/CT-guided salvage radiotherapy (sRT) in improving long-term biochemical recurrence-free survival (bRFS) in patients with biochemical recurrence (BCR) or PSA persistence (PERS) after radical prostatectomy (RP) for localized prostate cancer.

METHODS

This single-center retrospective study included 100 patients with BCR or PERS after RP who underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT and sRT according to EAU guidelines. The primary endpoint was bRFS (PSA ≤ 0.2 ng/ml).

RESULTS

Sixty-three patients had BCR and 37 had PERS. Fifteen patients had PSA pre-RT < 0.5 ng/ml, while 75 had PSA pre-RT ≥ 0.5 ng/ml. [⁶⁸Ga]Ga-PSMA-11 PET/CT was positive in 52 patients, with BCR patients more frequently exhibiting local recurrence while PERS patients showed more nodal involvement. Patients with PERS received sRT and androgen deprivation therapy (ADT) in 57% of cases. The hazard ratio (HR) of treatment failure for patients with PSA pre-RT ≥ 0.5 ng/ml vs. < 0.5 ng/ml was 2.2 (p < 0.039). With a median follow-up of 59 months, treatment failure occurred in 36% of patients, with no difference between BCR and PERS groups. Among those with treatment failure, 64% were [⁶⁸Ga]Ga-PSMA-11 PET/CT positive at recurrence, and 39% received a new PSMA PET/CT-based RT. All patients were alive at the last analysis.

CONCLUSION

[⁶⁸Ga]Ga-PSMA-11 PET/CT-guided sRT demonstrates significant long-term efficacy in patients with BCR or PERS after RP, leading to durable PSA response and guiding further treatment decisions.

TRIAL REGISTRATION

244/2016/O/Oss8 November 2016 retrospectively registered.

Controversies in the use of next-generation imaging for evaluation and treatment decision-making in patients with prostate cancer after biochemical recurrence: views from a Spanish expert panel

INTRODUCTION

Diagnosing and managing biochemical recurrence (BCR) of prostate cancer (PCa) following primary radical treatment remain a challenge. Implementing next-generation imaging (NGI) techniques has improved metastases detection. However, access to these techniques is heterogeneous, and controversies surround their use and subsequent treatment decisions. In November 2023, a multidisciplinary expert meeting was organized to discuss these aspects. This information was further reviewed in November 2024.

AREAS COVERED

NGI-specific tracers' selection, evidence supporting patient selection for NGI after BRC, current treatment strategies in patients with BRC, and the role of NGIs in current and future therapeutic approaches.

EXPERT OPINION

Despite improved detection performance compared to conventional imaging techniques, the application of NGIs to treatment decision-making and the impact on patient outcomes are yet to be proven. Given the lack of guidance, opinions and recommendations from multidisciplinary expert panels are valuable for diagnosing and adequately treating patients with BRC after radical treatment.

Implementation of PET/CT in radiation oncology-a patterns-of-care analysis of the German Society of Nuclear Medicine and the German Society of Radiation Oncology

BACKGROUND

The use of positron-emission tomography (PET)/computed tomography (CT) in radiation therapy (RT) has increased. Radiation oncologists (RadOncs) have access to PET/CT with a variety of tracers for different tumor entities and use it for target volume definition. The German Society of Nuclear Medicine (DGN) and the German Society of Radiation Oncology (DEGRO) aimed to identify current patterns of care in order to improve interdisciplinary collaboration.

METHODS

We created an online survey on participating RadOncs' use of PET tracers for different tumor entities and how they affect RT indication, dose prescription, and target volume definition. Further topics were reimbursement of PET/CT and organizational information (fixed timeslots and use of PET with an immobilization device [planning/RT-PET]). The survey contained 31 questions in German language (yes/no questions, multiple choice [MC] questions, multiple select [MS] questions, and free-text entry options). The survey was distributed twice via the DEGRO member mailing list.

RESULTS

During the survey period (May 22-August 7, 2023) a total of 156 RadOncs (13% of respondents) answered the survey. Among these, 59% reported access to diagnostic PET/CT within their organization/clinic and 24% have fixed timeslots for their patients. 37% of survey participants can perform RT-PET and 29% have the option of providing a dedicated RT technician for planning PET. Besides [18F]-fluorodeoxyglucose (FDG; mainly used in lung cancer: 95%), diagnostic prostate-specific membrane antigen (PSMA)-PET/CT for RT of prostate cancer is routinely used by 44% of participants (by 64% in salvage RT). Use of amino acid PET in brain tumors and somatostatin receptor PET in meningioma is low (19 and 25%, respectively). Scans are reimbursed through private (75%) or compulsory (55%) health insurance or as part of indications approved by the German Joint Federal Committee (Gemeinsamer Bundesausschuss; 59%). 98% of RadOncs agree that PET impacts target volume definition and 62% think that it impacts RT dose prescription.

DISCUSSION

This is the first nationwide survey on the role of PET/CT for RT planning among RadOncs in Germany. We find high acceptance of PET results for treatment decisions and target volume definition. Planning PET comes with logistic challenges for different healthcare settings (e.g., private practices vs. university hospitals). The decision to request PET/CT is often based on the possibility of reimbursement.

CONCLUSION

PET/CT has become an important tool for RadOncs, with several indications. However, access is still limited at several sites, especially for dedicated RT-PET. This study aims to improve interdisciplinary cooperation and adequate implementation of current guidelines for the treatment of various tumor entities.

EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer-2024 Update. Part I: Screening, Diagnosis, and Local Treatment with Curative Intent

BACKGROUND AND OBJECTIVE

The European Association of Urology (EAU)-European Association of Nuclear Medicine (EANM)-European Society for Radiotherapy and Oncology (ESTRO)-European Society of Urogenital Radiology (ESUR)-International Society of Urological Pathology (ISUP)-International Society of Geriatric Oncology (SIOG) guidelines provide recommendations for the management of clinically localised prostate cancer (PCa). This paper aims to present a summary of the 2024 version of the EAU-EANM-ESTRO-ESUR-ISUP-SIOG guidelines on the screening, diagnosis, and treatment of clinically localised PCa.

METHODS

The panel performed a literature review of all new data published in English, covering the time frame between May 2020 and 2023. The guidelines were updated, and a strength rating for each recommendation was added based on a systematic review of the evidence.

KEY FINDINGS AND LIMITATIONS

A risk-adapted strategy for identifying men who may develop PCa is advised, generally commencing at 50 yr of age and based on individualised life expectancy. The use of multiparametric magnetic resonance imaging in order to avoid unnecessary biopsies is recommended. When a biopsy is considered, a combination of targeted and regional biopsies should be performed. Prostate-specific membrane antigen positron emission tomography imaging is the most sensitive technique for identifying metastatic spread. Active surveillance is the appropriate management for men with low-risk PCa, as well as for selected favourable intermediate-risk patients with International Society of Urological Pathology grade group 2 lesions. Local therapies are addressed, as well as the management of persistent prostate-specific antigen after surgery. A recommendation to consider hypofractionation in intermediate-risk patients is provided. Patients with cN1 PCa should be offered a local treatment combined with long-term intensified hormonal treatment.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The evidence in the field of diagnosis, staging, and treatment of localised PCa is evolving rapidly. These PCa guidelines reflect the multidisciplinary nature of PCa management.

PATIENT SUMMARY

This article is the summary of the guidelines for "curable" prostate cancer. Prostate cancer is "found" through a multistep risk-based screening process. The objective is to find as many men as possible with a curable cancer. Prostate cancer is curable if it resides in the prostate; it is then classified into low-, intermediary-, and high-risk localised and locally advanced prostate cancer. These risk classes are the basis of the treatments. Low-risk prostate cancer is treated with "active surveillance", a treatment with excellent prognosis. For low-intermediary-risk active surveillance should also be discussed as an option. In other cases, active treatments, surgery, or radiation treatment should be discussed along with the potential side effects to allow shared decision-making.

Impact of 68Ga-PSMA PET/CT on radiation treatment planning of prostate cancer patients

AIM

This study aimed to assess the impact of 68Ga-PSMA PET/CT on radiation treatment (RT) planning in prostate cancer patients with salvage (sRT) or definitive (dRT) radiotherapy.

METHODS

38 patients (27 sRT, median PSA 0.79 ng/ml (range 0.06-12.1); 11 dRT, median PSA 4.35 ng/ml (range 1.55-55.5) underwent 68Ga-PSMA PET/CT before RT. Influence of 68Ga-PSMA PET/CT on the extent of planning target volume (PTV) and addition of PET-based boosts were assessed. Median follow up was 12 months (range 3-24).

RESULTS

68Ga-PSMA PET/CT showed positive findings in 23/38 patients (8/23: local recurrence (LR), 11/23: nodal metastasis, 1/23: LR and nodal, 2/23: solitary bone metastasis, 1/23: oligometastatic nodal/ bone metastases). In sRT primary PTV was changed in 16/27 patients extending the PTV to the lymphatic drainage (10/16), PSMA-positive LR (3/16), bone metastases (2/16) and both nodal/bone metastases (1/16). PET-based increase of primary PTV was 116%. PET-based boosts were administered in 19/27 patients (8/19: local, 10/19: nodal, 1/19: both), median boost volume was 31.3 cm3 (range 17.2-80.2) (local) and 19.7 cm3 (range 3.0-109.3) (nodal). PTV was changed in 1/11 (9%) of dRT patients (extension of primary PTV to the lymphatic drainage (RT volume of 644.5 cm3), additional nodal boost (volume of 2.7 cm3, 23.1 Gy)). All patients showed biochemical response (mean PSA decrease 88.8 +/- 14.0%). Nadir PSA was reached 10 months (range 1-17) after end of RT (median 0.07 ng/ml, range 0.002-3.96). Within a median 12 months follow-up (range 3-22/8-24 in sRT/dRT), median PSA was 0.05 ng/ml (range 0.002-8.5) (sRT) and 0.26 ng/ml (range 0.02-2.68) (dRT).

CONCLUSIONS

68Ga-PSMA PET/CT influenced sRT planning in almost 63% and dRT in 9% of patients by change of PTV and additional boosts.

Can 68 Ga-PSMA positron emission tomography and multiparametric MRI guide treatment for biochemical recurrence after radical prostatectomy?

OBJECTIVE

To evaluate the role of multiparametric magnetic resonance imaging (mpMRI) and Gallium-68 (68 Ga)-prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) in guiding salvage therapy for patients with biochemical recurrence (BCR) post-radical prostatectomy.

PATIENTS AND METHODS

Patients were evaluated with paired mpMRI and 68 Ga-PSMA PET/CT scans for BCR (prostate-specific antigen [PSA] >0.2 ng/mL). Patient, tumour, PSA and imaging characteristics were analysed with descriptive statistics.

RESULTS

A total of 117 patients underwent paired scans to investigate BCR, of whom 53.0% (62/117) had detectable lesions on initial scans and 47.0% (55/117) did not. Of those without detectable lesions, 8/55 patients proceeded to immediate salvage radiotherapy (sRT) and 47/55 were observed. Of patients with negative imaging who were initially observed, 46.8% (22/47) did not reach threshold for repeat imaging, while 53.2% were rescanned due to rising PSA levels. Of these rescanned patients, 31.9% (15/47) were spared sRT due to proven distant disease, or due to absence of disease on repeat imaging. Of the original 117 patients, 53 (45.3%) were spared early sRT due to absence of disease on imaging or presence of distant disease, while those undergoing delayed sRT still maintained good PSA responses. Of note, patients with high-risk features who underwent sRT despite negative imaging demonstrated satisfactory PSA responses to sRT. Study limitations include the observational design and absence of cause-specific or overall survival data.

CONCLUSION

Our findings support the use of mpMRI and 68 Ga-PSMA PET/CT in guiding timing and necessity of salvage therapy tailored to detected lesions, with potential to reduce unnecessary sRT-related morbidity. Larger or randomized trials are warranted to validate this.

PSMA-PET-guided dose-escalated volumetric arc therapy for newly diagnosed lymph node-positive prostate cancer: 5 Year outcomes following the FROGG and EviQ node-positive guidelines

INTRODUCTION

The Royal Australian and New Zealand College of Radiologists (RANZCR) Faculty of Radiation Oncology Genitourinary Group (FROGG) guidelines and online EviQ protocols incorporate prostate-specific membrane antigen (PSMA) positron emission tomography (PET)-guided dose-escalated intensity-modulated radiation therapy (DE-IMRT) for newly diagnosed lymph node (LN) positive prostate cancer. We evaluated late toxicity and efficacy outcomes following the FROGG and EviQ approach.

METHODS

Patients with LN-positive-only metastases on PSMA-PET imaging were offered curative therapy with 3 months neoadjuvant androgen deprivation therapy (ADT) followed by DE-IMRT and 3 years adjuvant ADT. IMRT was delivered via volumetric arc therapy (VMAT). We aimed to deliver 81 Gy in 45 fractions (Fx) to the prostate and PET-positive LNs, and 60 Gy in 45 Fx to elective pelvic nodes, contoured using the PIVOTAL guidelines.

RESULTS

Forty-five patients were included. The median number of PET-positive nodes boosted was 2 (range 1-6) and median boost volume 1.16 cc (range 0.15-4.14). Seventeen (38%) patients had PET-positive nodes outside of PIVOTAL contouring guidelines. With 60 months median follow-up, disease-free, metastasis-free, prostate cancer-specific and overall survival were 88.1%, 95.3%, 100% and 91.5%. There were no in-field nodal failures. Late grade 1, 2 and 3 gastrointestinal toxicities occurred in 4%, 2% and 0% of patients, and genitourinary toxicity in 18%, 18% and 4%. Lower limb grade 2 lymphoedema occurred in three patients (7%).

CONCLUSION

Outcomes following FROGG guidelines and EviQ are promising, with high long-term disease control and low toxicity. Contouring guidelines require modification due to the high rate of PET-positive nodes demonstrated beyond recommended coverage.

Metastatic Sites' Location and Impact on Patient Management After the Introduction of Prostate-specific Membrane Antigen Positron Emission Tomography in Newly Diagnosed and Biochemically Recurrent Prostate Cancer: A Critical Review

CONTEXT

The introduction of prostate-specific membrane antigen positron emission tomography (PSMA-PET) had a substantial impact on the management of prostate cancer (PCa) patients with a stage migration phenomenon and consequent treatment changes.

OBJECTIVE

To summarise the role of PSMA-PET to define the burden of disease through an accurate location of metastatic site(s) in PCa patients, describing the most common locations at PSMA-PET in the primary staging and recurrence setting, and to assess the clinical impact in the decision-making process.

EVIDENCE ACQUISITION

A comprehensive nonsystematic literature review was performed in April 2022. Literature search was updated until March 2022. The most relevant studies have been summarised, giving priority to registered clinical trials and multicentre collaborations.

EVIDENCE SYNTHESIS

PSMA-PET showed higher diagnostic accuracy than conventional imaging both in newly diagnosed PCa and in recurrent disease. This greater accuracy led to a migration of a higher proportion of patients identified with metastatic disease. Bone metastases were reported as the most frequent site of metastatic spread in staging (up to 17%) and restaging (up to 18%). In staging, considering the suboptimal sensitivity in lymph node metastasis detection prior to radical surgery, PSMA-PET should be performed in patients with high risk or unfavourable intermediate risk only, and it is not recommended to routinely avoid pelvic lymph node dissection in case of a negative scan. In case of prostate-specific antigen relapse, PSMA-PET had higher diagnostic accuracy than other diagnostic procedures in the early detection of the sites of recurrence, thus influencing the therapy decision-making process.

CONCLUSIONS

PSMA-PET detects a higher number of lesions than conventional imaging or other PET radiotracers, especially metastatic lesions unseen with other modalities. The high diagnostic accuracy of PSMA-PET leads to a significant patient upstage and thus an impact in clinical management, even if the overall impact on cancer mortality is still to be assessed.

PATIENT SUMMARY

Prostate-specific membrane antigen positron emission tomography (PSMA-PET) identifies metastatic lesions with higher accuracy than conventional imaging, both in primary prostate cancer and during disease recurrence. Skeletal metastasis and extrapelvic lymph nodes are the most common sites of metastatic spread. The high accuracy of PSMA-PET in the detection of metastatic disease led to a significant impact on patient management, even if the overall impact on cancer mortality is still to be assessed.

Oncologic outcomes of patients with lymph node invasion at prostatectomy and post-prostatectomy biochemical persistence

BACKGROUND

Pathologic nodal invasion at prostatectomy is frequently associated with persistently elevated prostate-specific antigen (PSA) and with increased risk of disease recurrence. Management strategies for these patients are poorly defined. We aimed to explore the long-term oncologic outcomes and patterns of disease progression.

METHODS

We included men treated between 2000 and 2017 who had lymph node invasion at radical prostatectomy and persistently detectable prostate-specific antigen post-prostatectomy. Postoperative imaging and management strategies were collated. Patterns of recurrence and probability of metastasis-free survival, prostate cancer-specific survival, and overall survival (OS) were assessed.

RESULTS

Among our cohort of 253 patients, 126 developed metastasis. Twenty-five had a positive scan within 6 months of surgery; of these, 15 (60%) had a nodal metastasis, 10 (40%) had a bone metastasis, and 4 (16%) had local recurrence. For metastasis-free survival, 5- and 10-year probabilities were 52% (95% CI 45%, 58%) and 37% (95% CI 28%, 46%), respectively. For prostate cancer-specific survival, 5- and 10-year probabilities were 89% (95% CI 84%, 93%) and 67% (95% CI 57%, 76%), respectively. A total of 221 patients proceeded to hormonal deprivation treatment alone. Ten patients received postoperative radiotherapy.

CONCLUSIONS

Biochemical persistence in patients with lymph node invasion is associated with high risk of disease progression and reduced prostate cancer-specific survival. Management was hindered by the limitation of imaging modalities utilized during the study period in accurately detecting residual disease. Novel molecular imaging may improve staging and help design a therapeutic strategy adapted to patients' specific needs.

Using PSMA imaging for prognostication in localized and advanced prostate cancer

The use of prostate-specific membrane antigen (PSMA)-directed applications in modern prostate cancer management has evolved rapidly over the past few years, helping to establish new treatment pathways and provide further insights into prostate cancer biology. However, the prognostic implications of PSMA-PET have not been studied systematically, owing to rapid clinical implementation without long follow-up periods to determine intermediate-term and long-term oncological outcomes. Currently available data suggest that traditional prognostic factors and survival outcomes are associated with high PSMA expression (both according to immunohistochemistry and PET uptake) in men with localized and biochemically recurrent disease. Treatment with curative intent (primary and/or salvage) often fails when PSMA-positive metastases are present; however, the sensitivity of PSMA-PET in detecting all metastases is poor. Low PSMA-PET uptake in recurrent disease is a favourable prognostic factor; however, it can be associated with poor prognosis in conjunction with high ¹⁸F-fluorodeoxyglucose uptake in metastatic castration-resistant prostate cancer. Clinical trials embedding PSMA-PET for guiding management with reliable oncological outcomes are needed to support ongoing clinical use.

Incorporating Prostate-specific Membrane Antigen Positron Emission Tomography in Management Decisions for Men with Newly Diagnosed or Biochemically Recurrent Prostate Cancer

CONTEXT

Prostate-specific membrane antigen (PSMA) is a promising molecular target for prostate cancer (PCa) that has allowed the development of a novel diagnostic approach to PCA in the primary and recurrent settings.

OBJECTIVE

To summarize available data and recommendations regarding the use of PSMA in newly diagnosed and recurrent PCa via a narrative review.

EVIDENCE ACQUISITION

A literature review was conducted using MEDLINE (via PubMed) and Scopus. The search strategy included meta-analyses, reviews, and original studies on staging and restaging with ⁶⁸Ga-PSMA positron emission tomography (PET)/computed tomography (CT).

EVIDENCE SYNTHESIS

Studies comparing PSMA-targeted imaging and conventional imaging suggest superior performance of PSMA-targeted imaging in primary and recurrent PCa, albeit with several clinically relevant limitations. Pretreatment ⁶⁸Ga-PSMA PET/CT allowed more accurate PCa staging in compared to routine practice for high-risk cases, and identified a number of otherwise unknown metastatic lesions. In biochemically recurrent PCa, PSMA PET can reveal sites of recurrence with greater sensitivity and specificity than conventional imaging, potentially detecting a major proportion of occult disease. This review will help providers in applying the most up-to-date and relevant literature to (1) determine which patients truly have oligometastatic disease and (2) ascertain who is most likely to experience a meaningful response to local consolidation in the biochemical recurrence setting.

CONCLUSIONS

Data on PSMA diagnostic studies in primary and recurrent PCa highlight the accuracy and clinical application of PSMA PET. While this review and the evidence to date might lead to a perception of superiority in metastasis directed therapy, fundamental lack of phase III clinical trials with clinically meaningful outcomes are yet to be determined.

PATIENT SUMMARY

PSMA (prostate-specific membrane antigen) scans have shown great promise for initial evaluation of prostate cancer (PCa) and in detection of PCa recurrence. The benefits are more apparent for initial staging of PCa. There are more limited clinical trial results for PCa recurrence on how best to use this new technique to guide cancer treatment.

Clinical Value of PET.CT Based on Big Data in Colorectal and Peritoneal Metastatic Cancer

This study focuses on the evaluation of the clinical utility of PET-CT imaging in peritoneal metastases and colorectal cancer. One hundred patients with colorectal peritoneal metastases, who underwent whole-body PET-CT imaging from January 2015 to December 2019, were selected as the experimental group, and 20 healthy individuals were selected as the control group. The SUVmax of the two groups of patients was 5.73 ± 3.84 and 2.70 ± 2.32, respectively, and the difference was statistically significant. The SUVmax AUC was 0.720, and the AUC of serum AFP, CEA, CA125, and CA199 were 0.596, 0.677, 0.642, and 0.696, respectively. Conclusion. 100 patients with colorectal and peritoneal metastatic cancer underwent PET/CT examination. The follow-up or other imaging examinations confirmed the diagnosis. Analysis of the ROC curve in this study found that with a peritoneal SUVmax> 3.2 as the diagnostic index for colorectal peritoneal metastatic cancer, the sum of sensitivity and specificity reached the maximum.

The Cellular and Molecular Immunotherapy in Prostate Cancer

In recent history, immunotherapy has become a viable cancer therapeutic option. However, over many years, its tenets have changed, and it now comprises a range of cancer-focused immunotherapies. Clinical trials are currently looking into monotherapies or combinations of medicines that include immune checkpoint inhibitors (ICI), CART cells, DNA vaccines targeting viruses, and adoptive cellular therapy. According to ongoing studies, the discipline should progress by incorporating patient-tailored immunotherapy, immune checkpoint blockers, other immunotherapeutic medications, hormone therapy, radiotherapy, and chemotherapy. Despite significantly increasing morbidity, immunotherapy can intensify the therapeutic effect and enhance immune responses. The findings for the immunotherapy treatment of advanced prostate cancer (PCa) are compiled in this study, showing that is possible to investigate the current state of immunotherapy, covering new findings, PCa treatment techniques, and research perspectives in the field’s unceasing evolution.

The Role of PSMA PET/CT in the Primary Diagnosis and Follow-Up of Prostate Cancer-A Practical Clinical Review

Simple Summary

The combination of positron emission tomography (PET)-diagnostics with ligands binding to the prostate-specific membrane antigen (PSMA) has been a diagnostic milestone in the situation of biochemical recurrence of prostate cancer and is gaining importance in primary diagnostics, providing a highly specific and sensitive diagnostic method in various clinical situations. However, the clinical application of this method requires a comprehensive knowledge of its advantages and disadvantages, potential pitfalls and influencing factors. This review aims to provide a practical clinical review of the currently available background data on PSMA PET/CT, as well as the clinical implications. Although a large amount of data already exist, a thorough analysis is complicated by study heterogeneity, showing the need for future systematic and prospective research.

Abstract

The importance of PSMA PET/CT in both primary diagnostics and prostate cancer recurrence has grown steadily since its introduction more than a decade ago. Over the past years, a vast amount of data have been published on the diagnostic accuracy and the impact of PSMA PET/CT on patient management. Nevertheless, a large heterogeneity between studies has made reaching a consensus difficult; this review aims to provide a comprehensive clinical review of the available scientific literature, covering the currently known data on physiological and pathological PSMA expression, influencing factors, the differences and pitfalls of various tracers, as well as the clinical implications in initial TNM-staging and in the situation of biochemical recurrence. This review has the objective of providing a practical clinical overview of the advantages and disadvantages of the examination in various clinical situations and the body of knowledge available, as well as open questions still requiring further research.

Clinicopathological and oncological significance of persistent prostate-specific antigen after radical prostatectomy: A systematic review and meta-analysis

Objective

To investigate the association of persistently elevated prostate-specific antigen (PSA) after radical prostatectomy (RP) with clinicopathological features and long-term oncological prognosis for the development of a potential management strategy.

Methods

A systematic literature search was performed using PubMed and Web of Science up to June 2021 to identify the eligible studies focusing on understanding the impact of persistent PSA in patients who underwent RP for localized prostate cancer. Meta-analyses were performed on parameters with available information.

Results

A total of 32 RP studies were identified, of which 11 included 26 719 patients with consecutive cohorts and the remaining 21 comprised 24 177 patients with cohorts carrying specific restrictions. Of the 11 studies with consecutive cohorts, the incidence of persistent PSA varied between 3.1% and 34.6% with a median of 11.0%. Meta-analyses revealed patients with persistent PSA consistently showed unfavorable clinicopathological features and a more than 3.5-fold risk of poorer biochemical recurrence, metastasis, and prostate cancer-specific mortality prognosis independently, when compared to patients with undetectable PSA. Similarly, cases with persistent PSA in different specific patient cohorts with a higher risk of prostate cancer also showed a trend of worse outcomes.

Conclusion

We found that the frequency of persistent PSA was about 11.0% in consecutive RP cohorts. Persistent PSA was significantly associated with unfavorable clinicopathological characteristics and worse oncological outcomes. Patients with persistent PSA after RP may benefit from early salvage treatment to delay or prevent biochemical recurrence, improving oncological outcomes for these patients. Further prospective randomized controlled trials are warranted to understand optimal systemic therapy in these patients.

The impact of PSMA PET on the treatment and outcomes of men with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

BACKGROUND

Prostate-specific membrane antigen (PSMA) PET is highly sensitive in identifying disease recurrence in men with biochemical recurrence of prostate cancer (BCR) after primary therapy and is rapidly being adopted in clinical practice. The purpose of this systematic review and meta-analysis was to assess the documented impact of PSMA-PET on patient management and outcomes, including prostate-specific antigen (PSA) response, and intermediate and long-term outcome measures.

MATERIALS AND METHODS

MBASE, PubMed, Web of Science, Cochrane and OVID databases were searched for studies reporting on the impact of PSMA-PET on the management and outcomes of patients with BCR after definitive primary therapy. Outcome measures assessed included biochemical response to therapy after PET and BCR-free survival (BRFS). The proportions of patients in whom management changed, and the proportion of patients in whom each outcome measure was obtained were tabulated and pooled into meta-analysis using DerSimonian-Laird method.

RESULTS

A total of 34 studies with 3680 men reported change in management after PSMA-PET and 27 studies with 2639 men reported on at least one outcome measure and had follow-up data. PSMA-PET was positive in 2508/3680 (68.2%). The pooled proportion of change in management after PSMA-PET was 56.4% (95% CI, 48.0-63.9%). A decrease in serum PSA was documented in 72.4% of men (95% CI, 63.4-81.5%), and complete biochemical response in 23.3% (95% CI, 14.6-32.0%) at a median follow-up of 8.1 and 11 months, respectively. The pooled BRFS rate was 60.2% (95% CI, 49.1-71.4%) at a median follow-up of 20 months.

CONCLUSION

In conclusion, PSMA PET is positive in more than 2/3 of men with BCR and impacts patient management in more than half of the men. BRFS after PET-directed management is 60% at a median of 20 months after salvage therapy, and complete biochemical response may be achieved in up to a quarter of men.

PSMA and Choline PET for the Assessment of Response to Therapy and Survival Outcomes in Prostate Cancer Patients: A Systematic Review from the Literature

Simple Summary

Radiolabeled choline and PSMA PET have been largely tested in the initial staging of prostate cancer and for biochemical recurrence. Moreover, diverse data are now available about their role in the evaluation of response to local and systematic therapies, and their predictive impact on the prognosis, before and after therapy. Therefore, in the present systematic review, we aimed to describe the available data, to summarize the current evidence in these settings of disease.

Abstract

The aims of this systematic review were to (1) assess the utility of PSMA-PET and choline-PET in the assessment of response to systemic and local therapy, and to (2) determine the value of both tracers for the prediction of response to therapy and survival outcomes in prostate cancer. We performed a systematic literature search in PubMed/Scopus/Google Scholar/Cochrane/EMBASE databases (between January 2010 and October 2021) accordingly. The quality of the included studies was evaluated following the “Quality Assessment of Prognostic Accuracy Studies” tool (QUAPAS-2). We selected 40 articles: 23 articles discussed the use of PET imaging with [⁶⁸Ga]PSMA-11 (16 articles/1123 patients) or [¹¹C]/[¹⁸F]Choline (7 articles/356 patients) for the prediction of response to radiotherapy (RT) and survival outcomes. Seven articles (three with [⁶⁸Ga]PSMA-11, three with [¹¹C]Choline, one with [¹⁸F]Choline) assessed the role of PET imaging in the evaluation of response to docetaxel (as neoadjuvant therapy in one study, as first-line therapy in five studies, and as a palliative regimen in one study). Seven papers with radiolabeled [¹⁸F]Choline PET/CT (n = 121 patients) and three with [⁶⁸Ga]PSMA-11 PET (n = 87 patients) were selected before and after enzalutamide/abiraterone acetate. Finally, [¹⁸F]Choline and [⁶⁸Ga]PSMA-11 PET/CT as gatekeepers for the treatment of metastatic prostate cancer with Radium-223 were assessed in three papers. In conclusion, in patients undergoing RT, radiolabeled choline and [⁶⁸Ga]PSMA-11 have an important prognostic role. In the case of systemic therapies, the role of such new-generation imaging techniques is still controversial without sufficient data, thus requiring additional in this scenario.

Targeting PSMA Revolutionizes the Role of Nuclear Medicine in Diagnosis and Treatment of Prostate Cancer

Targeting the prostate-specific membrane antigen (PSMA) protein has become of great clinical value in prostate cancer (PCa) care. PSMA positron emission tomography/computed tomography (PET/CT) is increasingly used in initial staging and restaging at biochemical recurrence in patients with PCa, where it has shown superior detection rates compared to previous imaging modalities. Apart from targeting PSMA for diagnostic purposes, there is a growing interest in developing ligands to target the PSMA-protein for radioligand therapy (RLT). PSMA-based RLT is a novel treatment that couples a PSMA-antibody to (alpha or beta-emitting) radionuclide, such as Lutetium-177 (177Lu), to deliver high radiation doses to tumor cells locally. Treatment with 177Lu-PSMA RLT has demonstrated a superior overall survival rate within randomized clinical trials as compared to routine clinical care in patients with metastatic castration-resistant prostate cancer (mCRPC). The current review provides an overview of the literature regarding recent developments in nuclear medicine related to PSMA-targeted PET imaging and Theranostics.

Combining External Beam Radiation and Radionuclide Therapies: Rationale, Radiobiology, Results and Roadblocks

The emergence of effective radionuclide therapeutics, such as radium-223 dichloride, [177Lu]Lu-DOTA-TATE and [177Lu]Lu-PSMA ligands, over the last 10 years is driving a rapid expansion in molecular radiotherapy (MRT) research. Clinical trials that are underway will help to define optimal dosing protocols and identify groups of patients who are likely to benefit from this form of treatment. Clinical investigations are also being conducted to combine new MRT agents with other anticancer drugs, with particular emphasis on DNA repair inhibitors and immunotherapeutics. In this review, the case is presented for combining MRT with external beam radiotherapy (EBRT). The technical and dosimetric challenges of combining two radiotherapeutic modalities have impeded progress in the past. However, the need for research into the specific radiobiological effects of radionuclide therapy, which has lagged behind that for EBRT, has been recognised. This, together with innovations in imaging technology, MRT dosimetry tools and EBRT hardware, will facilitate the future use of this important combination of treatments.

Salvage therapy for prostate cancer after radical prostatectomy

More than 40% of men with intermediate-risk or high-risk prostate cancer will experience a biochemical recurrence after radical prostatectomy. Clinical guidelines for the management of these patients largely focus on the use of salvage radiotherapy with or without systemic therapy. However, not all patients with biochemical recurrence will go on to develop metastases or die from their disease. The optimal pre-salvage therapy investigational workup for patients who experience biochemical recurrence should, therefore, include novel techniques such as PET imaging and genomic analysis of radical prostatectomy specimen tissue, as well as consideration of more traditional clinical variables such as PSA value, PSA kinetics, Gleason score and pathological stage of disease. In patients without metastatic disease, the only known curative intervention is salvage radiotherapy but, given the therapeutic burden of this treatment, importance must be placed on accurate timing of treatment, radiation dose, fractionation and field size. Systemic therapy also has a role in the salvage setting, both concurrently with radiotherapy and as salvage monotherapy.

Outcome after PSMA-PET/CT-based salvage radiotherapy for nodal recurrence after radical prostatectomy

Purpose

Nodal recurrent prostate cancer (PCa) represents a common state of disease, amenable to local therapy. PSMA-PET/CT detects PCa recurrence at low PSA levels. The aim of this study was to evaluate the outcome of PSMA-PET/CT-based salvage radiotherapy (sRT) for lymph node (LN) recurrence.

Methods

A total of 100 consecutive patients treated with PSMA-PET/CT-based salvage elective nodal radiotherapy (sENRT) for LN recurrence were retrospectively examined. Patients underwent PSMA-PET/CT scan due to biochemical persistence (bcP, 76%) or biochemical recurrence (bcR, 24%) after radical prostatectomy (RP). Biochemical recurrence-free survival (BRFS) defined as PSA < post-RT nadir + 0.2 ng/ml and distant metastasis-free survival (DMFS) were calculated using the Kaplan–Meier method and uni- and multivariate analysis was performed.

Results

Median follow-up was 37 months. Median PSA at PSMA-PET/CT was 1.7 ng/ml (range 0.1–40.1) in patients with bcP and 1.4 ng/ml (range 0.3–5.1) in patients with bcR. PSMA-PET/CT detected 1, 2, and 3 or more LN metastases in 35%, 23%, and 42%, respectively. Eighty-three percent had only pelvic, 2% had only paraaortic, and 15% had pelvic and paraaortic LN metastases. Cumulatively, a total dose converted to EQD2_1.5 Gy of 66 Gy (60–70 Gy) was delivered to the prostatic fossa, 70 Gy (66–72 Gy) to the local recurrence, if present, 65.1 Gy (56–66 Gy) to PET-positive lymph nodes, and 47.5 Gy (42.4–50.9 Gy) to the lymphatic pathways. Concomitant androgen deprivation therapy (ADT) was administered in 83% of patients. One-, 2-, and 3-year BRFS was 80.7%, 71.6%, and 65.8%, respectively. One-, 2-, and 3-year DMFS was 91.6%, 79.1%, and 66.4%, respectively. In multivariate analysis, concomitant ADT, longer ADT duration (≥ 12 vs. < 12 months) and LN localization (pelvic vs. paraaortic) were associated with improved BRFS and concomitant ADT and lower PSA value before sRT (< 1 vs. > 1 ng/ml) with improved DMFS, respectively. No such association was seen for the number of affected lymph nodes.

Conclusions

Overall, the present analysis shows that the so far, unmatched sensitivity and specificity of PSMA-PET/CT translates in comparably high BRFS and DMFS after PSMA-PET/CT-based sENRT for patients with PCa LN recurrence. Concomitant ADT, duration of ADT, PSA value before sRT, and localization of LN metastases were significant factors for improved outcome.

Benefits of early salvage therapy on oncological outcomes in high-risk prostate cancer with persistent PSA after radical prostatectomy

BACKGROUND

Patients with prostate-specific antigen (PSA) persistence are at the increased risk of disease progression. The aim of our study was to evaluate the impact of early salvage therapy on oncological outcomes in patients with persistent PSA after radical prostatectomy (RP).

METHODS

Within a single tertiary centre database, we identified men with persistent (≥ 0.1 ng/ml) versus undetectable (< 0.1 ng/ml) PSA 4-8 weeks after RP for high-risk prostate cancer (HRPCa). The cumulative incidence function was used to estimate cancer-specific survival (CSS) and clinical progression-free survival (CPFS). The Kaplan-Meier method was used to estimate overall survival (OS). The effects on oncological outcomes of salvage radiotherapy (SRT) ± androgen deprivation therapy (ADT) vs. ADT monotherapy were tested in the subgroup of patients with persistent PSA.

RESULTS

Of 414 consecutive patients who underwent RP for HRPC, 125 (30.2%) had persistent PSA. Estimated 10-year CPFS, CSS and OS for men with persistent vs. undetectable PSA were 63.8% vs. 93.5%, 78.5% vs. 98.3% and 54% vs. 83.2% (all p < 0.0001), respectively. In men with persistent PSA, ADT alone was associated with higher risk (hazard ratio (HR) for worse CSS (HR 3.9, p = 0.005) and OS (HR 4.7, p < 0.0001) but not for CP (HR 1.6, p = 0.2) when compared with SRT ± ADT.

CONCLUSION

In patients who underwent RP for HRPCa, persistent PSA was associated with poor oncological outcomes. Early SRT ± ADT resulted in significantly improved CSS and OS in men with persistent PSA comparing with early androgen deprivation monotherapy.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

[68Ga]Ga-P16-093 as a PSMA-Targeted PET Radiopharmaceutical for Detection of Cancer: Initial Evaluation and Comparison with [68Ga]Ga-PSMA-11 in Prostate Cancer Patients Presenting with Biochemical Recurrence

PURPOSE

This study was undertaken to evaluate radiation dosimetry for the prostate-specific membrane antigen targeted [⁶⁸Ga]Ga-P16-093 radiopharmaceutical, and to initially assess agent performance in positron emission tomography (PET) detection of the site of disease in prostate cancer patients presenting with biochemical recurrence.

PROCEDURES

Under IND 133,222 and an IRB-approved research protocol, we evaluated the biodistribution and pharmacokinetics of [⁶⁸Ga]Ga-P16-093 with serial PET imaging following intravenous administration to ten prostate cancer patients with biochemical recurrence. The recruited subjects were all patients in whom a recent [⁶⁸Ga]Ga-PSMA-11 PET/X-ray computed tomography (CT) exam had been independently performed under IND 131,806 to assist in decision-making with regard to their clinical care. Voided urine was collected from each subject at ~ 60 min and ~ 140 min post-[⁶⁸Ga]Ga-P16-093 injection and assayed for Ga-68 content. Following image segmentation to extract tissue time-activity curves and corresponding cumulated activity values, radiation dosimetry estimates were calculated using IDAC Dose 2.1. The prior [⁶⁸Ga]Ga-PSMA-11 PET/CT exam (whole-body PET imaging at 60 min post-injection, performed with contrast-enhanced diagnostic CT) served as a reference scan for comparison to the [⁶⁸Ga]Ga-P16-093 findings.

RESULTS

[⁶⁸Ga]Ga-P16-093 PET images at 60 min post-injection provided diagnostic information that appeared equivalent to the subject's prior [⁶⁸Ga]Ga-PSMA-11 scan. With both radiopharmaceuticals, sites of tumor recurrence were found in eight of the ten patients, identifying 16 lesions. The site of recurrence was not detected with either agent for the other two subjects. Bladder activity was consistently lower with [⁶⁸Ga]Ga-P16-093 than [⁶⁸Ga]Ga-PSMA-11. The kidneys, spleen, salivary glands, and liver receive the highest radiation exposure from [⁶⁸Ga]Ga-P16-093, with estimated doses of 1.7 × 10^-1, 6.7 × 10^-2, 6.5 × 10^-2, and 5.6 × 10^-2 mGy/MBq, respectively. The corresponding effective dose from [⁶⁸Ga]Ga-P16-093 is 2.3 × 10^-2 mSv/MBq.

CONCLUSIONS

[⁶⁸Ga]Ga-P16-093 provided diagnostic information that appeared equivalent to [⁶⁸Ga]Ga-PSMA-11 in this limited series of ten prostate cancer patients presenting with biochemical recurrence, with the kidneys found to be the critical organ. Diminished tracer appearance in the urine represents a potential advantage of [⁶⁸Ga]Ga-P16-093 over [⁶⁸Ga]Ga-PSMA-11 for detection of lesions in the pelvis.

Use and Impact of Positron Emission Tomography/Computed Tomography Prior to Salvage Radiation Therapy in Men with Biochemical Recurrence After Radical Prostatectomy: A Scoping Review

CONTEXT

The use, common findings, and impact of modern molecular positron emission tomography (PET)/computed tomography (CT) imaging prior to salvage radiation therapy (RT) in men with biochemical recurrence after radical prostatectomy (RP) have not been evaluated comprehensively.

OBJECTIVE

We performed a scoping systematic review of the literature assessing detection rates, detection patterns, changes in management, as well as changes in patient outcome resulting from molecular PET/CT imaging using three molecular tracers: 18F-fluciclovine, 8Ga prostate-specific membrane antigen (PSMA)-11, and 18F-DCFPyL.

EVIDENCE ACQUISITION

A computerized bibliographic search of the Medline/PubMed database was carried out from inception to October 1, 2020. We included published reports and abstracts evaluating the utility of 1Fluciclovine, 68Ga-PSMA-11, and 18F-DCFPyL PET in the detection of recurrent disease in the post-RP, pre-salvage RT setting. Outcomes of interest were extracted and tabulated, and existing evidence was synthesized qualitatively.

EVIDENCE SYNTHESIS

A total of 45 studies were included in our qualitative synthesis. Detection rates were high across most studies, and there was often a clear relationship between prostate-specific antigen (PSA) level and positive imaging findings. Though limited randomized data are available, there appears to be increased sensitivity with the use of PSMA ligands compared with fluciclovine at low PSA values. Most studies have shown that only one-third to one-half of patients with detected lesions have lesions in the prostatic fossa alone. Management changes occur in nearly 50% of patients undergoing molecular imaging, and biochemical response in patients who undergo molecular PET-based RT planning appears to be statistically superior to the response in patients who undergo conventional imaging -based RT planning alone. High biochemical responses from molecular PET-based salvage RT, ranging from 45% to 94%, did not appear to come at the expense of increased genitourinary or gastrointestinal toxicity. The presence or absence of avid lesions appears to be a strong prognostic factor.

CONCLUSIONS

Molecular PET/CT imaging in the post-RP, pre-salvage RT setting often triggers management changes that result from detecting lesions in locations not typically included in consensus-driven postoperative RT fields. Ongoing trials will assess the benefit of PSMA PET in guiding salvage RT following RP and determine its impact on long-term outcomes.

PATIENT SUMMARY

We reviewed and reported detection rates, detection patterns, and changes in management resulting from molecular positron emission tomography/computed tomography imaging in men with biochemically recurrent prostate cancer following radical prostatectomy. Prior to the receipt of salvage radiation therapy, molecular tracers targeting prostate-specific membrane antigen appear to be especially sensitive at identifying the place where prostate cancer has come back after surgery, which can help radiation oncologists better target the recurrent disease and potentially improve the rates of cure from prostate cancer in this setting. Future studies will determine whether these imaging tools will change cure rates and side effects, but early results are promising.

A survey among German-speaking radiation oncologists on PET-based radiotherapy of prostate cancer

Background

Positron emission tomography-(PET) has evolved as a powerful tool to guide treatment for prostate cancer (PC). The aim of this survey was to evaluate the acceptance and use of PET—especially with prostate-specific membrane antigen (PSMA) targeting tracers—in clinical routine for radiotherapy (RT) and the impact on target volume definition and dose prescription.

Methods

We developed an online survey, which we distributed via e-mail to members of the German Society of Radiation Oncology (DEGRO). The survey included questions on patterns of care of RT for PC with/without PET. For evaluation of doses we used the equivalent dose at fractionation of 2 Gy with α/β = 1.5 Gy [EQD2(1.5 Gy)].

Results

From 109 participants, 78.9% have the possibility to use PET for RT planning. Most centers use PSMA-targeting tracers (98.8%). In 39.5%, PSMA-PET for biochemical relapse after prior surgery is initiated at PSA ≥ 0.5 ng/mL, while 30.2% will perform PET at ≥ 0.2 ng/mL (≥ 1.0 ng/mL: 16.3%, ≥ 2.0 ng/mL: 2.3%, regardless of PSA: 11.7%). In case of PET-positive local recurrence (LR) and pelvic lymph nodes (LNs), 97.7% and 96.5% of the participants will apply an escalated dose. The median total dose in EQD2(1.5 Gy) was 70.00 Gy (range: 56.89–85.71) for LR and 62.00 Gy (range: 52.61–80.00) for LNs. A total number of ≤ 3 (22.0%) or ≤ 5 (20.2%) distant lesions was most often described as applicable for the definition as oligometastatic PC.

Conclusion

PSMA-PET is widely used among German radiation oncologists. However, specific implications on treatment planning differ among physicians. Therefore, further trials and guidelines for PET-based RT are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01811-8.

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.

Radiotherapy of oligometastatic prostate cancer: a systematic review

BACKGROUND

Due to improved imaging sensitivity, the term "oligometastatic" prostate cancer disease is diagnosed more often, leading to an increasing interest in metastasis-directed therapy (MDT). There are two types of radiation based MDT applied when treating oligometastatic disease: (1) stereotactic body radiation therapy (SBRT) generally used for bone metastases; or (2) SBRT for isolated nodal oligometastases combined with prophylactic elective nodal radiotherapy. This review aims to summarize current evidence data, which may shed light on the optimal management of this heterogeneous group of patients.

METHODS

A systematic review of the Medline database through PubMed was performed according to PRISMA guidelines. All relevant studies published up to November 2020 were identified and screened. Fifty-six titles were included. Besides outcome parameters, different prognostic and predictive factors were assessed, including site of metastases, time between primary treatment and MDT, use of systemic therapies, hormone sensitivity, as well as pattern of recurrence.

FINDINGS

Evidence consists largely of retrospective case series and no consistent precise definition of oligometastasis exists, however, most investigators seem to acknowledge the need to distinguish between patients presenting with what is frequently called "synchronous" versus "metachronous" oligometastatic disease. Available data on radiotherapy as MDT demonstrate high local control rates and a small but relevant proportion of patients without progressive disease after 2 years. This holds true for both hormone sensitive and castration resistant prostate cancer diseases. The use of 68Ga-PSMA PET/CT for staging increased dramatically. Radiation doses and field sizes varied considerably among the studies. The search for relevant prognostic and predictive factors is ongoing.

CONCLUSIONS

To our best knowledge this review on oligometastatic prostate cancer included the largest number of original articles. It demonstrates the therapeutic potential and challenges of MDT for oligometastatic prostate cancer. Prospective studies are under way and will provide further high-level evidence.

Management of Persistently Elevated Prostate-specific Antigen After Radical Prostatectomy: A Systematic Review of the Literature

CONTEXT

The prognosis and optimal management of pN0/pN1 patients with persistently elevated prostate-specific antigen (PSA) 6-8 wk after radical prostatectomy (RP) remain unclear.

OBJECTIVE

To perform a systematic review of oncologic outcomes and effectiveness of salvage therapies in men with a detectable PSA level after RP.

EVIDENCE ACQUISITION

A systematic review was performed in May 2020. A total of 2374 articles were screened, and 25 studies including 5217 men were selected and included in the systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

EVIDENCE SYNTHESIS

PSA persistence was most commonly defined as PSA >0.1 ng/ml. PSA persistence was significantly correlated with disease aggressiveness and associated with worse oncologic outcomes than in men with undetectable PSA levels. The 5-yr recurrence-free survival rates varied from 21.5% to 67.0%. The ≥10-yr cancer-specific survival was 75-88%. Salvage radiotherapy ± androgen deprivation therapy was associated with improved survival outcomes. Risk stratification according to pathologic features, PSA levels/kinetics, and genomic classifier may aid in personalization of treatment. The usefulness of molecular imaging in this setting remains underevaluated. Main limitations of this systematic review are the retrospective design of the included studies and the lack of randomized controlled trials (RCTs) focusing on this specific population.

CONCLUSIONS

PSA persistence after RP is strongly correlated with poor oncologic outcomes. Our review suggests a benefit from immediate radiotherapy; however, current evidence is still low. Indication of subsequent therapies should be based on individual discussions, taking into account all the prognostic factors and the efficacy/toxicity imbalance of proposed treatment. Results from ongoing RCTs are awaited to state on the role of more intensified systemic therapy in this population.

PATIENT SUMMARY

Patients with a detectable prostate-specific antigen level after surgery are at high risk of subsequent progression. Immediate radiotherapy might improve survival outcomes. Further research into the role of molecular imaging and genomic classifier is needed in this patient population.

EAU-EANM-ESTRO-ESUR-SIOG Guidelines on Prostate Cancer-2020 Update. Part 1: Screening, Diagnosis, and Local Treatment with Curative Intent

OBJECTIVE

To present a summary of the 2020 version of the European Association of Urology (EAU)-European Association of Nuclear Medicine (EANM)-European Society for Radiotherapy and Oncology (ESTRO)-European Society of Urogenital Radiology (ESUR)-International Society of Geriatric Oncology (SIOG) guidelines on screening, diagnosis, and local treatment of clinically localised prostate cancer (PCa).

EVIDENCE ACQUISITION

The panel performed a literature review of new data, covering the time frame between 2016 and 2020. The guidelines were updated and a strength rating for each recommendation was added based on a systematic review of the evidence.

EVIDENCE SYNTHESIS

A risk-adapted strategy for identifying men who may develop PCa is advised, generally commencing at 50 yr of age and based on individualised life expectancy. Risk-adapted screening should be offered to men at increased risk from the age of 45 yr and to breast cancer susceptibility gene (BRCA) mutation carriers, who have been confirmed to be at risk of early and aggressive disease (mainly BRAC2), from around 40 yr of age. The use of multiparametric magnetic resonance imaging in order to avoid unnecessary biopsies is recommended. When a biopsy is performed, a combination of targeted and systematic biopsies must be offered. There is currently no place for the routine use of tissue-based biomarkers. Whilst prostate-specific membrane antigen positron emission tomography computed tomography is the most sensitive staging procedure, the lack of outcome benefit remains a major limitation. Active surveillance (AS) should always be discussed with low-risk patients, as well as with selected intermediate-risk patients with favourable International Society of Urological Pathology (ISUP) 2 lesions. Local therapies are addressed, as well as the AS journey and the management of persistent prostate-specific antigen after surgery. A strong recommendation to consider moderate hypofractionation in intermediate-risk patients is provided. Patients with cN1 PCa should be offered a local treatment combined with long-term hormonal treatment.

CONCLUSIONS

The evidence in the field of diagnosis, staging, and treatment of localised PCa is evolving rapidly. The 2020 EAU-EANM-ESTRO-ESUR-SIOG guidelines on PCa summarise the most recent findings and advice for their use in clinical practice. These PCa guidelines reflect the multidisciplinary nature of PCa management.

PATIENT SUMMARY

Updated prostate cancer guidelines are presented, addressing screening, diagnosis, and local treatment with curative intent. These guidelines rely on the available scientific evidence, and new insights will need to be considered and included on a regular basis. In some cases, the supporting evidence for new treatment options is not yet strong enough to provide a recommendation, which is why continuous updating is important. Patients must be fully informed of all relevant options and, together with their treating physicians, decide on the most optimal management for them.

Patterns of Lymph Node Failure in Patients With Recurrent Prostate Cancer Postradical Prostatectomy and Implications for Salvage Therapies

PURPOSE

There is increasing use of radical prostatectomy to treat patients with high-risk prostate cancer. This has contributed toward a pathologic stage migration, and a greater number of patients are subsequently being diagnosed with biochemical failure. There is increasing use of advanced imaging techniques in the setting of biochemical failure, including positron emission tomography-computed tomography (PET-CT).

METHODS AND MATERIALS

This critical literature review highlights the evidence for PET-CT in postprostatectomy biochemical failure and identifies sites of pelvic lymph node relapse in the setting of biochemical failure and the potential implications that the locations of these relapses may have for salvage therapies. Potential future directions are then considered.

RESULTS

The optimal PET-CT tracer remains uncertain but there is increasing use of prostate-specific membrane antigen PET-CT for investigating sites of nodal metastasis at low prostate-specific antigen levels, and this is leading to a blurring of the biochemical and radiologic recurrence phases. The optimal therapeutic approach remains undefined, with current trials investigating postoperative radiation therapy to the whole pelvis in addition to the prostatic fossa, the use of PET-CT in the setting of biochemical recurrence to guide delivery of salvage radiation therapy, and, for patients with node-only relapsed prostate cancer, the addition of whole pelvis radiation therapy to metastasis-directed therapies such as stereotactic ablative radiotherapy.

CONCLUSIONS

The most appropriate target volume for salvage radiation therapy remains uncertain, and the findings of studies using PET-CT to map nodal recurrences suggest that there could be a role for extending whole pelvis radiation therapy volumes to increase coverage of superior nodal regions. The emerging fields of radiomics and radiogenomics could provide important prognostic information and aid decision making for patients with relapsed prostate cancer.

[F18] FDG-PET/CT for manual or semiautomated GTV delineation of the primary tumor for radiation therapy planning in patients with esophageal cancer: is it useful?

Background

Target volume definition of the primary tumor in esophageal cancer is usually based on computed tomography (CT) supported by endoscopy and/or endoscopic ultrasound and can be difficult given the low soft-tissue contrast of CT resulting in large interobserver variability. We evaluated the value of a dedicated planning [F18] FDG-Positron emission tomography/computer tomography (PET/CT) for harmonization of gross tumor volume (GTV) delineation and the feasibility of semiautomated structures for planning purposes in a large cohort.

Methods

Patients receiving a dedicated planning [F18] FDG-PET/CT (06/2011–03/2016) were included. GTV was delineated on CT and on PET/CT (GTV_CT and GTV_PET/CT, respectively) by three independent radiation oncologists. Interobserver variability was evaluated by comparison of mean GTV and mean tumor lengths, and via Sørensen–Dice coefficients (DSC) for spatial overlap. Semiautomated volumes were constructed based on PET/CT using fixed standardized uptake values (SUV) thresholds (SUV30, 35, and 40) or background- and metabolically corrected PERCIST-TLG and Schaefer algorithms, and compared to manually delineated volumes.

Results

45 cases were evaluated. Mean GTV_CT and GTV_PET/CT were 59.2/58.0 ml, 65.4/64.1 ml, and 60.4/59.2 ml for observers A–C. No significant difference between CT- and PET/CT-based delineation was found comparing the mean volumes or lengths. Mean Dice coefficients on CT and PET/CT were 0.79/0.77, 0.81/0.78, and 0.8/0.78 for observer pairs AB, AC, and BC, respectively, with no significant differences. Mean GTV volumes delineated semiautomatically with SUV30/SUV35/SUV40/Schaefer’s and PERCIST-TLG threshold were 69.1/23.9/18.8/18.6 and 70.9 ml. The best concordance of a semiautomatically delineated structure with the manually delineated GTV_CT/GTV_PET/CT was observed for PERCIST-TLG.

Conclusion

We were not able to show that the integration of PET/CT for GTV delineation of the primary tumor resulted in reduced interobserver variability. The PERCIST-TLG algorithm seemed most promising compared to other thresholds for further evaluation of semiautomated delineation of esophageal cancer.

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.

Recent advances of PET imaging in clinical radiation oncology

Radiotherapy and radiation oncology play a key role in the clinical management of patients suffering from oncological diseases. In clinical routine, anatomic imaging such as contrast-enhanced CT and MRI are widely available and are usually used to improve the target volume delineation for subsequent radiotherapy. Moreover, these modalities are also used for treatment monitoring after radiotherapy. However, some diagnostic questions cannot be sufficiently addressed by the mere use standard morphological imaging. Therefore, positron emission tomography (PET) imaging gains increasing clinical significance in the management of oncological patients undergoing radiotherapy, as PET allows the visualization and quantification of tumoral features on a molecular level beyond the mere morphological extent shown by conventional imaging, such as tumor metabolism or receptor expression. The tumor metabolism or receptor expression information derived from PET can be used as tool for visualization of tumor extent, for assessing response during and after therapy, for prediction of patterns of failure and for definition of the volume in need of dose-escalation. This review focuses on recent and current advances of PET imaging within the field of clinical radiotherapy / radiation oncology in several oncological entities (neuro-oncology, head & neck cancer, lung cancer, gastrointestinal tumors and prostate cancer) with particular emphasis on radiotherapy planning, response assessment after radiotherapy and prognostication.

Sensitivity of CE-MRI in detecting local recurrence after radical prostatectomy

AIM

The aim of our study was to evaluate the sensitivity of contrast-enhanced magnetic resonance (CE-MR) with phased array coil in the diagnosis of local recurrence in patients with prostate cancer after radical prostatectomy and referred for salvage radiotherapy (SRT).

MATERIALS AND METHODS

This retrospective study included 73 patients treated with SRT after radical prostatectomy in the period between September 2006 and November 2017. All patients performed a CE-MRI with phased array coil before the start of SRT. A total of 213 patients treated at the ASST Grande Ospedale Metropolitano Niguarda in the period between September 2006 and November 2017 with SRT after radical prostatectomy were reviewed. Seventy-three patients with a CE-MRI with phased array coil of the pelvis before the start of SRT were included in the present study.

RESULTS

At imaging review, recurrence local recurrent disease was diagnosed in 48 of 73 patients. By considering as reference standard the decrease in prostate-specific antigen (PSA) value after radiotherapy, we defined: 41 true positive (patients with MRI evidence of local recurrence and PSA value decreasing after SRT), 7 false positive (patients with MRI evidence of local recurrence without biochemical response after SRT), 3 true negative (patients without MRI evidence of local recurrence and stable or increased PSA value after SRT) and 22 false negative (patients without MRI evidence of local recurrence and PSA value decreasing after SRT) cases. The sensitivity values were calculated in relation to the PSA value before the start of treatment, obtaining a value of 74% for PSA above 0.2 ng/mL.

CONCLUSION

The sensitivity of CE-MRI in local recurrence detection after radical prostatectomy increases with increasing PSA values. CE-MRI with phased array coil can detect local recurrences after radical prostatectomy with a good sensitivity in patients with pre-RT PSA value above 0.2 ng/mL.

PSMA-PET guided dose-escalated volumetric arc therapy (VMAT) for newly diagnosed lymph node positive prostate cancer: Efficacy and toxicity outcomes at two years

PURPOSE/OBJECTIVES

There are no published reports of prostate specific membrane antigen (PSMA) positron emission tomography (PET) guided dose-escalated intensity-modulated radiation therapy (DE-IMRT) in newly diagnosed lymph node (LN) positive prostate cancer. We report early toxicity and efficacy outcomes with this approach.

MATERIALS/METHODS

Patients with newly diagnosed high-risk prostate cancer were staged using PSMA PET, computed tomography (CT) and bone scans. Patients with LN positive-only metastases were offered curative therapy using 3 months androgen deprivation therapy (ADT) followed by DE-IMRT (using volumetric arc therapy), and 3 years adjuvant ADT. All patients had fiducial marker insertion, with privately insured patients having spacer hydrogel insertion. PET and prostate magnetic resonance imaging were fused with the planning CT. We aimed to deliver 81 Gy in 45 fractions (Fx) to the prostate and PET-positive LNs, and 60 Gy in 45Fx to bilateral elective pelvic LNs.

RESULTS

In all, 46 patients were treated, with 83% Gleason 8-10, 67% T3/T4, median number of LNs 2 (range 1-6), and median PET-positive LN volume 1.14 cc (range 0.15-4.14). LNs were outside of standard contouring guidelines in 37% of patients. The mean PET-positive LN clinical target volume dose ranged from 73.3 to 85.9 Gy (median 83.6 Gy). With 24 months median follow-up, two year failure-free survival was 100%, and 2 year overall survival 95.7%. Acute grade 1 and 2 GI toxicity occurred in 48 and 11% of patients, and GU toxicity in 72 and 24%. Late grade 1, 2 and 3 GI toxicity occurred in 13, 2 and 0%, and GU toxicity 28, 13 and 4%. No toxicity was attributable to the high dose LN boost.

CONCLUSIONS

PSMA PET-guided DE-IMRT up to 81 Gy to the prostate and involved LNs, and long term ADT, is a promising approach for newly diagnosed LN positive prostate cancer. LN contouring guidelines require re-evaluation in the era of PSMA PET imaging.

Detection Rate and Localization of Prostate Cancer Recurrence Using 68Ga-PSMA-11 PET/MRI in Patients with Low PSA Values ≤ 0.5 ng/mL

A first analysis of simultaneous ⁶⁸Ga-prostate-specific membrane antigen (PSMA)-11 PET/MRI showed some improvement in the detection of recurrent disease at low serum prostate specific antigen (PSA) values below 0.5 ng/mL compared with the already high detection rate of ⁶⁸Ga-PSMA-11 PET/CT. We therefore focused on all patients with biochemical recurrence and PSA values no higher than 0.5 ng/mL to assess the detection rate for ⁶⁸Ga-PSMA-11 PET/MRI. Methods: We retrospectively analyzed a cohort of 66 consecutive patients who underwent ⁶⁸Ga-PSMA-11 PET/MRI for biochemical recurrence with a PSA value no higher than 0.5 ng/mL at our institution. Median PSA level was 0.23 ng/mL (range, 0.03-0.5 ng/mL). Detection of PSMA-positive lesions within the prostate fossa, local and distant lymph nodes, bones, or visceral organs was recorded. In addition, all scans with ⁶⁸Ga-PSMA-11 PET/MRI-positive lesions were retrospectively assessed to analyze if lesions were detected inside or outside a standard salvage radiotherapy volume. Results: Overall, in 36 of 66 patients (54.5%) PSMA-positive lesions were detected; in 26 of 40 (65%) patients with a PSA level between 0.2 and 0.5 ng/mL and in 10 of 26 (38.5%) patients with a PSA level less than 0.2 ng/mL. Even at those low PSA values, only 8 of 66 (12.1%) patients had exclusive local recurrence. Lymph nodes were detected in 23 patients and bone metastases in 5 on ⁶⁸Ga-PSMA-11 PET/MRI. In 26 of 66 patients (39.4%), PSMA-positive lesions were located outside a standard salvage radiotherapy volume. Conclusion: Our data confirm that ⁶⁸Ga-PSMA-11 PET/MRI has a high detection rate for recurrent prostate cancer, even at low PSA levels no higher than 0.5 ng/mL. In addition, we show that ⁶⁸Ga-PSMA-11 PET/MRI detected PSMA-positive lesions outside a standard salvage radiotherapy volume in 39.4% of all patients.

The impact of prostate-specific antigen persistence after radical prostatectomy on the efficacy of salvage radiotherapy in patients with primary N0 prostate cancer

OBJECTIVE

To test whether salvage radiotherapy (SRT) in patients with lymph node negative (N0) prostate cancer is equally effective with persistent prostate-specific antigen (PSA) and PSA rising from the undetectable range (<0.1 ng/mL) after radical prostatectomy (RP).

PATIENTS AND METHODS

We assessed post-SRT PSA progression-free survival (PFS) in 555 patients with prostate cancer. The entire cohort was compared with a risk-adjusted subgroup of 112 patient pairs with matching pre-RP PSA level (±10 ng/mL), Gleason score (≤6 vs 7 vs ≥8), and pre-SRT PSA level (±0.5 ng/mL).

RESULTS

The median follow-up was 6.1 years. After RP, PSA was undetectable in 422 and persistent in 133 patients. PSA persistence and a pre-SRT PSA level of ≥0.5 ng/mL reduced Kaplan-Meier rates of PFS significantly. In multivariate analysis of the entire cohort and after risk adjustment, the pre-SRT PSA level but not post-RP PSA persistence was a significant parameter. In the matched cohort's subgroup with early SRT at a PSA level of <0.5 ng/mL, a trend towards a worse outcome with post-RP PSA persistence was observed. Delayed SRT with a PSA level ≥0.5 ng/mL led to a PFS of <30%, irrespective of the post-RP PSA level.

CONCLUSION

In patients with N0 prostate cancer with post-RP PSA persistence, early SRT at a PSA level <0.5 ng/mL seems to be less effective than in recurrent patients with post-RP undetectable PSA. They might benefit from intensified therapy, but larger case numbers are required to substantiate this conclusion. In patients with a PSA level ≥0.5 ng/mL and higher-risk features associated with post-RP PSA persistence, SRT alone is unlikely to provide long-term freedom from further progression.

Consensus on molecular imaging and theranostics in prostate cancer

Rapid developments in imaging and treatment with radiopharmaceuticals targeting prostate cancer pose issues for the development of guidelines for their appropriate use. To tackle this problem, international experts representing medical oncologists, urologists, radiation oncologists, radiologists, and nuclear medicine specialists convened at the European Association of Nuclear Medicine Focus 1 meeting to deliver a balanced perspective on available data and clinical experience of imaging in prostate cancer, which had been supported by a systematic review of the literature and a modified Delphi process. Relevant conclusions included the following: diphosphonate bone scanning and contrast-enhanced CT are mentioned but rarely recommended for most patients in clinical guidelines; MRI (whole-body or multiparametric) and prostate cancer-targeted PET are frequently suggested, but the specific contexts in which these methods affect practice are not established; sodium fluoride-18 for PET-CT bone scanning is not widely advocated, whereas gallium-68 or fluorine-18 prostate-specific membrane antigen gain acceptance; and, palliative treatment with bone targeting radiopharmaceuticals (rhenium-186, samarium-153, or strontium-89) have largely been replaced by radium-223 on the basis of the survival benefit that was reported in prospective trials, and by other systemic therapies with proven survival benefits. Although the advances in MRI and PET-CT have improved the accuracy of imaging, the effects of these new methods on clinical outcomes remains to be established. Improved communication between imagers and clinicians and more multidisciplinary input in clinical trial design are essential to encourage imaging insights into clinical decision making.

MR-guidance in clinical reality: current treatment challenges and future perspectives

Magnetic Resonance-guided radiotherapy (MRgRT) marks the beginning of a new era. MR is a versatile and suitable imaging modality for radiotherapy, as it enables direct visualization of the tumor and the surrounding organs at risk. Moreover, MRgRT provides real-time imaging to characterize and eventually track anatomical motion. Nevertheless, the successful translation of new technologies into clinical practice remains challenging. To date, the initial availability of next-generation hybrid MR-linac (MRL) systems is still limited and therefore, the focus of the present preview was on the initial applicability in current clinical practice and on future perspectives of this new technology for different treatment sites.MRgRT can be considered a groundbreaking new technology that is capable of creating new perspectives towards an individualized, patient-oriented planning and treatment approach, especially due to the ability to use daily online adaptation strategies. Furthermore, MRL systems overcome the limitations of conventional image-guided radiotherapy, especially in soft tissue, where target and organs at risk need accurate definition. Nevertheless, some concerns remain regarding the additional time needed to re-optimize dose distributions online, the reliability of the gating and tracking procedures and the interpretation of functional MR imaging markers and their potential changes during the course of treatment. Due to its continuous technological improvement and rapid clinical large-scale application in several anatomical settings, further studies may confirm the potential disruptive role of MRgRT in the evolving oncological environment.

68Ga-PSMA PET/CT-based metastasis-directed radiotherapy for oligometastatic prostate cancer recurrence after radical prostatectomy

PURPOSE

The aim of this communication was to assess the efficacy of directed oligometastatic radiotherapy (RT) based on ⁶⁸Ga-PSMA PET/CT in patients with prostate cancer (PCa) biochemical relapse (BCR) after primary treatment with curative intent.

METHODS

This is a retrospective analysis of a monocentric cohort of PCa patients diagnosed with oligometastatic disease on ⁶⁸Ga-PSMA PET/CT and treated with metastasis-directed RT. Inclusion criteria were: histologically proven PCa, BCR after primary treatment with curative intent, oligometastatic disease defined as ≤ 3 metastatic lesions. To evaluate the efficacy of the therapy, biochemical response defined as a decrease of > 50% of PSA (PSA₅₀) was measured at 1 and 4 months. Patients were followed up until progression and start of androgen deprivation therapy (ADT). BCR-free survival and ADT-free survival were calculated.

RESULTS

20 patients met the inclusion criteria. Median PSA value: 1.4 ng/ml (IQR, 0.3-2.3 ng/ml). A total of 30 PSMA-positive lesions were treated: 18 lymph nodes (60%), nine bone (30%) and three visceral lesions (10%). Median follow-up was 15 months (range 4-33 months). Biochemical response at 1 and 4 months was found in 3/20 patients (15%) and 14/20 (70%), respectively. BCR-free survival rate at 1 year was 79% and 53% at 2 years. ADT-free survival at 2 years was 74%.

CONCLUSION

This retrospective study suggests that metastasis-directed RT based on ⁶⁸Ga-PSMA PET/CT may be a valuable treatment in patients with PCa oligometastatic disease, providing promising BCR-free survival rates and potentially postponing ADT for at least 2 years in 74% of the patients. Response assessment should not be measured before 4 months after treatment.

Randomized prospective phase III trial of 68Ga-PSMA-11 PET/CT molecular imaging for prostate cancer salvage radiotherapy planning [PSMA-SRT]

BACKGROUND

Salvage radiotherapy (SRT) for prostate cancer (PCa) recurrence after prostatectomy offers long-term biochemical control in about 50-60% of patients. SRT is commonly initiated in patients with serum PSA levels < 1 ng/mL, a threshold at which standard-of-care imaging is insensitive for detecting recurrence. As such, SRT target volumes are usually drawn in the absence of radiographically visible disease. 68Ga-PSMA-11 (PSMA) PET/CT molecular imaging is highly sensitive and may offer anatomic localization of PCa biochemical recurrence. However, it is unclear if incorporation of PSMA PET/CT imaging into the planning of SRT could improve its likelihood of success. The purpose of this trial is to evaluate the success rate of SRT for recurrence of PCa after prostatectomy with and without planning based on PSMA PET/CT.

METHODS

We will randomize 193 patients to proceed with standard SRT (control arm 1, n = 90) or undergo a PSMA PET/CT scan (free of charge for patients) prior to SRT planning (investigational arm 2, n = 103). The primary endpoint is the success rate of SRT measured as biochemical progression-free survival (BPFS) after initiation of SRT. Biochemical progression is defined by PSA ≥ 0.2 ng/mL and rising. The randomization ratio of 1:1.13 is based on the assumption that approximately 13% of subjects randomized to Arm 2 will not be treated with SRT because of PSMA-positive extra-pelvic metastases. These patients will not be included in the primary endpoint analysis but will still be followed. The choice of treating the prostate bed alone vs prostate bed and pelvic lymph nodes, with or without androgen deprivation therapy (ADT), is selected by the treating radiation oncologist. The radiation oncologist may change the radiation plan depending on the findings of the PSMA PET/CT scan. Any other imaging is allowed for SRT planning in both arms if done per routine care. Patients will be followed until either one of the following conditions occur: 5 years after the date of initiation of randomization, biochemical progression, diagnosis of metastatic disease, initiation of any additional salvage therapy, death.

DISCUSSION

This is the first randomized phase 3 prospective trial designed to determine whether PSMA PET/CT molecular imaging can improve outcomes in patients with PCa early BCR following radical prostatectomy.

ACRONYM

PSMA-SRT Phase 3 trial.

CLINICAL TRIAL REGISTRATION

■ IND#130649 ◦ Submission: 04.26.2016 ◦ Safe-to-proceed letter issued by FDA: 05.25.2016 ■ UCLA IRB #18-000484, ■ First submission: 3.27.2018 ■ Date of approval: 5.31.2018 ■ UCLA JCCC Short Title NUC MED 18-000484 ■ NCI Trial Identifier NCI-2018-01518 ■ ClinicalTrials.gov Identifier NCT03582774 ■ First Submitted: 06.19.2018 ■ First Submitted that Met QC Criteria: 06.27.2018 ■ First Posted: 07.11.2018 ■ Last Update Submitted that Met QC Criteria: 07.17.2018 ■ Last Update Posted: 07.19.2018 TRIAL STATUS: Current Trial Status Active as of 08/13/2018 Trial Start Date 09/01/2018-Actual Primary Completion Date 09/01/2023-Anticipated Trial Completion Date 09/01/2024-Anticipated.

Impact of 68Ga-PSMA PET/CT on the Radiotherapeutic Approach to Prostate Cancer in Comparison to CT: A Retrospective Analysis

⁶⁸Ga-prostate-specific membrane antigen PET/CT (⁶⁸Ga-PSMA PET/CT) offers unprecedented accuracy for staging of primary, persistent, or recurrent prostate cancer. Thus, we hypothesized that ⁶⁸Ga-PSMA PET/CT before radiotherapy significantly affects the radiotherapeutic approach in comparison to the current standard, a CT-based approach. Methods: Between February 2014 and December 2017, 172 patients underwent ⁶⁸Ga-PSMA PET/CT before radiotherapy and were included in this retrospective analysis. Twenty-two (13%) patients were referred for primary definitive radiotherapy, 51% (88/172) for prostate-specific antigen (PSA) persistence, and 36% (62/172) for PSA recurrence after radical prostatectomy. An experienced radiation oncologist, masked to the CT and PET/CT results, decided on the radiation treatment management of all patients on the basis of the clinical and pathologic variables. The potential increase in diagnostic accuracy, and the subsequent change in radiotherapeutic approach, were documented separately for PET/CT versus CT. Results: The overall detection rate was 70% (120/172) for ⁶⁸Ga-PSMA PET/CT. Patients with a pre-PET/CT PSA level of more than 0.5 ng/mL (98/111; 88%) had PET-positive results significantly more often. Overall, PSMA PET/CT revealed 171 lesions, PET alone 156, and CT alone 85. For all patients, a continuous diagnostic increase in positive findings was observed for primary tumor/local recurrence (CT, 18%, vs. PET/CT, 37%), pelvic lymph nodes (CT, 21%, vs. PET/CT, 44%), and distant metastases (CT, 7%, vs. PET/CT, 19%) when comparing CT with PET/CT. Compared with CT, the combination of PET/CT information resulted in a change in treatment in 107 of 172 (62%) patients, that is, 8 of 22 (36%) patients before any treatment, 31 of 62 (50%) with PSA recurrence, and 68 of 88 (77%) with PSA persistence. Comparing the different radiotherapy indications with one another, there was a higher rate of change in management for postoperative patients than for patients before any treatment. Conclusion: Compared with conventional CT, ⁶⁸Ga-PSMA PET/CT had a remarkable impact on radiotherapeutic approach, especially in postoperative patients. Thus, considering the growing amount of data on the impact of ⁶⁸Ga-PSMA PET/CT on postoperative patients, ⁶⁸Ga-PSMA PET/CT has recently been endorsed by a few cancer guidelines as an imaging modality in patients with PSA persistence or recurrence (e.g., the German S3 guideline and the European Association of Urology guideline).