Imaging techniques for local recurrence of prostate cancer: for whom, why and how?

Precision Medicine Approach in Prostate Cancer

Prostate cancer is the most prevalent type of cancer and the second cause of death in men worldwide. Various diagnostic and treatment procedures are available for this type of malignancy, but High-grade or locally advanced prostate cancers showed the potential to develop to lethal phase that can be causing dead. Therefore, new approaches are needed to prolong patients' survival and to improve their quality of life. Precision medicine is a novel emerging field that plays an essential role in identifying new sub-classifications of diseases and in providing guidance in treatment that is based on individual multi-omics data. Multi-omics approaches include the use of genomics, transcriptomics, proteomics, metabolomics, epigenomics and phenomics data to unravel the complexity of a disease-associated biological network, to predict prognostic biomarkers, and to identify new targeted drugs for individual cancer patients. We review the impact of multi-omics data in the framework of systems biology in the era of precision medicine, emphasising the combination of molecular imaging modalities with highthroughput techniques and the new treatments that target metabolic pathways involved in prostate cancer.

Management of Isolated Local Failures Following Stereotactic Body Radiation Therapy for Low to Intermediate Risk Prostate Cancer

Background: Stereotactic body radiation therapy (SBRT) is a safe and effective treatment option for patients with low to intermediate risk prostate cancer (1). SBRT results in very low PSA nadirs secondary to the delivery of high biologically effective doses. Studies reporting on the diagnosis, confirmation, and management of salvageable isolated local failures (ILF) are limited. This study aims to determine the incidence and management approach of ILF after SBRT in a large single institution cohort. Method: All patients with low or intermediate risk localized prostate cancer treated with SBRT at Georgetown University Hospital were eligible for this study. Treatment was delivered using robotic SBRT with doses of 35-36.25 Gy in five fractions. ILF were diagnosed using multiparametric MRI and/or biopsy prompted by rising PSA levels after achieving long-term nadir. Patient's characteristics were extracted from a prospective institutional quality of life trial (IRB 2009-510). Type of salvage therapy and post-salvage PSA were determined on subsequent follow-up and chart review. Results: Between December 2008 to August 2018, 998 men with low to intermediate risk prostate cancer were eligible for inclusion in this analysis. Twenty-four patients (low risk, n = 5; intermediate risk, n = 19) were found to have ILF within the prostate on either MRI (n = 19) and/or biopsy (n = 20). Median pre-treatment PSA was 7.55 ng/ml. Median time to diagnosis of ILF was 72 months (24-110 months) with median PSA at the time of ILF of 2.8 ng/ml (0.7-33 ng/ml). Median PSA doubling time was 17 months (5-47 months). Thirteen patients with biopsy proven ILF proceeded with salvage therapy (cryotherapy n = 12, HIFU n = 1). Of 12 patients who underwent cryotherapy, 7 had a post-treatment PSA of <0.1 ng/ml. One patient experienced a urethral-cutaneous fistula (grade 3 toxicity). Conclusion: The incidence of isolated local recurrence is rare in our cohort. Diagnosis and management of isolated local failures post-SBRT continues to evolve. Our report highlights the importance of early utilization of MRI and confirmatory biopsy at relatively low PSA levels and long PSA doubling time (1). Additionally, undetectable PSA levels after salvage therapy supports the role of early treatment in ILF (1). Further research is needed to determine appropriate patient selection and salvage modality in this population.

Focal HIFU therapy for anterior compared to posterior prostate cancer lesions

Objective

To compare cancer control in anterior compared to posterior prostate cancer lesions treated with a focal HIFU therapy approach.

Materials and methods

In a prospectively maintained national database, 598 patients underwent focal HIFU (Sonablate^®500) (March/2007–November/2016). Follow-up occurred with 3-monthly clinic visits and PSA testing in the first year with PSA, every 6–12 months with mpMRI with biopsy for MRI-suspicion of recurrence. Treatment failure was any secondary treatment (ADT/chemotherapy, cryotherapy, EBRT, RRP, or re-HIFU), tumour recurrence with Gleason ≥ 3 + 4 on prostate biopsy without further treatment or metastases/prostate cancer-related mortality. Cases with anterior cancer were compared to those with posterior disease.

Results

267 patients were analysed following eligibility criteria. 45 had an anterior focal-HIFU and 222 had a posterior focal-HIFU. Median age was 64 years and 66 years, respectively, with similar PSA level of 7.5 ng/ml and 6.92 ng/ml. 84% and 82%, respectively, had Gleason 3 + 4, 16% in both groups had Gleason 4 + 3, 0% and 2% had Gleason 4 + 4. Prostate volume was similar (33 ml vs. 36 ml, p = 0.315); median number of positive cores in biopsies was different in anterior and posterior tumours (7 vs. 5, p = 0.009), while medium cancer core length, and maximal cancer percentage of core were comparable. 17/45 (37.8%) anterior focal-HIFU patients compared to 45/222 (20.3%) posterior focal-HIFU patients required further treatment (p = 0.019).

Conclusion

Treating anterior prostate cancer lesions with focal HIFU may be less effective compared to posterior tumours.

Diagnostic performance of imaging techniques for detecting of local recurrence after prostate brachytherapy

PURPOSE

The purpose of this study was to evaluate MRI and fluorocholine PET/CT diagnostic performances for the detection of local recurrence following prostate brachytherapy for localised prostate cancer.

MATERIAL AND METHODS

In this single-centre study, we retrospectively reviewed data from 21 patients treated by brachytherapy for localised prostate cancer and diagnosed with biochemical recurrence according to Phoenix Criteria, who underwent MRI and fluorocholine PET/CT. We included patients with local relapse suspicion according to imaging exams, with biopsy for the final assessment of local recurrence. Patient analysis data were supplemented by segment analysis using an 8-segment model.

RESULTS

The fluorocholine PET/CT was positive for 81% and negative for 19% of patients. The sensitivity and specificity were 92% and 33% with diagnosis accuracy of 67%. The MRI was positive for 57% and negative for 43% of patients. The sensitivity and specificity were 67% and 56% with diagnosis accuracy of 62%. There was no statistically significant difference between fluorocholine PET/CT and MRI accuracy (P=0.63). On a segment-based analysis, the sensitivity and specificity were 44% and 82% for fluorocholine PET/CT with diagnosis accuracy of 78%. For MRI, specificity was 91% diagnosis accuracy was 82%.

CONCLUSION

Both MRI and fluorocholine PET/CT permit to highlight local recurrence sites after prostate brachytherapy. Confirmation biopsies are, however, necessary since this accuracy is insufficient.

Contrast-Enhanced Transrectal Ultrasound in Focal Therapy for Prostate Cancer

PURPOSE OF REVIEW

Contrast-enhanced transrectal ultrasound (CeTRUS) is an emerging imaging technique in prostate cancer (PCa) diagnosis and treatment. We review the utility and implications of CeTRUS in PCa focal therapy (FT).

RECENT FINDINGS

CeTRUS utilizes intravenous injection of ultrasound-enhancing agents followed by high-resolution ultrasound to evaluate tissue microvasculature and differentiate between benign tissue and PCa, with the latter demonstrating increased enhancement. The potential utility of CeTRUS in FT for PCa extends to pre-, intra- and post-operative settings. CeTRUS may detect PCa, facilitate targeted biopsy and aid surgical planning prior to FT. During FT, the treated area can be visualized as a well-demarcated non-enhancing zone and continuous real-time assessment allows immediate re-treatment if necessary. Following FT, the changes on CeTRUS are immediate and consistent, thus facilitating repeat imaging for comparison during follow-up. Areas suspicious for recurrence may be detected and target-biopsied. Enhancement can be quantified using time-intensity curves allowing objective assessment and comparison. Based on encouraging early outcomes, CeTRUS may become an alternative imaging modality in prostate cancer FT. Further study with larger cohorts and longer follow-up are needed.

The utility of PET-based imaging for prostate cancer biochemical recurrence: a systematic review and meta-analysis

INTRODUCTION

Conventional imaging modalities have been poor in characterizing the true extent of disease in men with biochemical recurrence following primary treatment for prostate cancer. Functional imaging with positron emission tomography (PET) has shown promise of being a superior imaging modality. We conducted a systematic review and meta-analysis to define the diagnostic accuracy of PET/CT using 11C-choline, 18F-FACBC, or 68Ga-PSMA in detecting recurrent prostate cancer.

METHODS

We searched multiple databases in line with the preferred reporting items for systematic review and meta-analysis (PRISMA) statement to define the diagnostic accuracy of 11C-choline, 18F-FACBC, or 68Ga-PSMA PET/CT. Only studies secondarily staging participants with biochemical recurrence and those with an appropriate reference standard (pathology, further imaging, and/or clinical response) were eligible for analysis.

RESULTS

Twenty-one studies with 3202 participants met the inclusion criteria. Of these, 11C-choline, 18F-FACBC, and 68Ga-PSMA were the tracer investigated in 16, 5, and 1 studies, respectively. The summary sensitivity for each tracer was 80.9% (95% CI 70.4-88.3%), 79.7% (95% CI 51.9-93.4%), and 76.4% (95% CI 68.3-82.9%), respectively. The corresponding summary specificity was 84.1% (95% CI 70.2-92.2%), 61.9% (95% CI 41.1-79.0%), and 99.8% (95% CI 97.5-100%), respectively. Detection rates ranged between 58.6 and 82.8%. All included studies were judged to be at high risk of bias primarily due to study limitations pertaining to the reference standard.

CONCLUSION

There is a lack of high-quality data to verify the accuracy of PET-based imaging using 11C-choline, 18F-FACBC, or 68Ga-PSMA. The early results are encouraging that these techniques are superior to conventional imaging modalities, which would allow salvage therapies to be optimized.

A review discussing fluciclovine (18F) PET/CT imaging in the detection of recurrent prostate cancer

A significant number of patients radically treated for prostate cancer (PCa) will develop prostate-specific antigen recurrence (27-53%). Localizing the anatomical site of relapse is critical, in order to achieve the optimal treatment management. To date the diagnostic accuracy of standard imaging is low. Several desirable features have been identified for the amino-acid-based PET agent, fluciclovine (¹⁸F) including: long ¹⁸F half-life which allows more practical use in centers without a cyclotron onsite; acting as a substrate for amino acid transporters upregulated in PCa or associated with malignant phenotype; lacking of incorporation into protein; and limited urinary excretion. Fluciclovine (¹⁸F) is currently approved both in USA and Europe with specific indication in adult men with suspected recurrent PCa based on elevated prostate-specific antigen following prior treatment.

Management of Biochemical Recurrence after Primary Curative Treatment for Prostate Cancer: A Review

How to manage patients with prostate cancer (PCa) with biochemical recurrence (BCR) following primary curative treatment is a controversial issue. Importantly, this prostate-specific antigen (PSA)-only recurrence is a surrogate neither of PCa-specific survival nor of overall survival. Physicians are therefore challenged with preventing or delaying the onset of clinical progression in those deemed at risk, while avoiding over-treating patients whose disease may never progress beyond PSA-only recurrence. Adjuvant therapy for radical prostatectomy (RP) or local radiotherapy (RT) has a role in certain at-risk patients, although it is not recommended in low-risk PCa owing to the significant side-effects associated with RT and androgen deprivation therapy (ADT). The recommendations for salvage therapy differ depending on whether BCR occurs after RP or primary RT, and in either case, definitive evidence regarding the best strategy is lacking. Options for treatment of BCR after RP are RT at least to the prostatic bed, complete or intermittent ADT, or observation; for BCR after RT, salvage RP, cryotherapy, complete or intermittent ADT, brachytherapy, high-intensity focused ultrasound (HIFU), or observation can be considered. Many patient- and cancer-specific factors need to be taken into account when deciding on the best strategy, and optimal management depends on the involvement of a multidisciplinary team, consultation with the patient themselves, and the adoption of an individualised approach. Improvements in imaging techniques may enable earlier detection of metastases, which will hopefully refine future management decisions.

Practical aspects of prostate MRI: hardware and software considerations, protocols, and patient preparation

The use of multiparametric MRI scans for the evaluation of men with prostate cancer has increased dramatically and is likely to continue expanding as new developments come to practice. However, it has not yet gained the same level of acceptance of other imaging tests. Partly, this is because of the use of suboptimal protocols, lack of standardization, and inadequate patient preparation. In this manuscript, we describe several practical aspects of prostate MRI that may facilitate the implementation of new prostate imaging programs or the expansion of existing ones.

Value of bimodal (18)F-choline-PET/MRI and trimodal (18)F-choline-PET/MRI/TRUS for the assessment of prostate cancer recurrence after radiation therapy and radical prostatectomy

Between 27% and 53% of all patients who undergo radical prostatectomy (RP) or radiation therapy (RT) as the first-line treatment of prostate cancer (PCa) develop a biochemical recurrence. Imaging plays a pivotal role in restaging by helping to distinguish between local relapse and metastatic disease (i.e., lymph-node and skeletal metastases). At present, the most promising tools for assessing PCa patients with biochemical recurrence are multiparametric magnetic resonance imaging (mpMRI) and positron emission tomography (PET)/computed tomography (CT) with radio-labeled choline derivatives. The main advantage of mpMRI is its high diagnostic accuracy in detecting local recurrence, while choline-PET/CT is able to identify lymph-node metastases when they are not suspicious on morphological imaging. The most recent advances in the field of fusion imaging have shown that multimodal co-registration, synchronized navigation, and combined interpretation are more valuable than the individual; separate assessment offered by different diagnostic techniques. The objective of the present essay was to describe the value of bimodal choline-PET/mpMRI fusion imaging and trimodal choline-PET/mpMRI/transrectal ultrasound (TRUS) in the assessment of PCa recurrence after RP and RT. Bimodal choline-PET/mpMRI fusion imaging allows morphological, functional, and metabolic information to be combined, thereby overcoming the limitations of each separate imaging modality. In addition, trimodal real-time choline-PET/mpMRI/TRUS fusion imaging may be useful for the planning and real-time guidance of biopsy procedures in order to obtain histological confirmation of the local recurrence.

A Domain Constrained Deformable (DoCD) Model for Co-registration of Pre- and Post-Radiated Prostate MRI

External beam radiation treatment (EBRT) is a popular method for treating prostate cancer (CaP) involving destroying tumor cells with ionizing radiation. Following EBRT, biochemical failure has been linked with disease recurrence. However, there is a need for methods for evaluating early treatment related changes to allow for an early intervention in case of incomplete disease response. One method for looking at treatment evaluation is to detect changes in MRI markers on a voxel-by-voxel basis following treatment. Changes in MRI markers may be correlated with disease recurrence and complete or partial response. In order to facilitate voxel-by-voxel imaging related treatment changes, and also to evaluate morphologic changes in the gland post treatment, the pre- and post-radiated MRI must first be brought into spatial alignment via image registration. However, EBRT induces changes in the prostate volume and distortion to the internal anatomy of the prostate following radiation treatment. The internal substructures of the prostate, the central gland (CG) and peripheral zone (PZ), may respond to radiation differently, and their resulting shapes may change drastically. Biomechanical models of the prostate that have been previously proposed tend to focus on how external forces affect the surface of the prostate (not the internals), and assume that the prostate is a volume-preserving entity. In this work we present DoCD, a biomechanical model for automatically registering pre-, post-EBRT MRI with the aim of expressly modeling the (1) changes in volume, and (2) changes to the CG and PZ. DoCD was applied to a cohort of 30 patients and achieved a root mean square error of 2.994 mm, which was statistically significantly better a traditional biomechanical model which did not consider changes to the internal anatomy of the prostate (mean of 5.071 mm).

A prospective development study investigating focal irreversible electroporation in men with localised prostate cancer: Nanoknife Electroporation Ablation Trial (NEAT)

Introduction

Focal therapy may reduce the toxicity of current radical treatments while maintaining the oncological benefit. Irreversible electroporation (IRE) has been proposed to be tissue selective and so might have favourable characteristics compared to the currently used prostate ablative technologies. The aim of this trial is to determine the adverse events, genito-urinary side effects and early histological outcomes of focal IRE in men with localised prostate cancer.

Methods

This is a single centre prospective development (stage 2a) study following the IDEAL recommendations for evaluating new surgical procedures. Twenty men who have MRI-visible disease localised in the anterior part of the prostate will be recruited. The sample size permits a precision estimate around key functional outcomes. Inclusion criteria include PSA ≤ 15 ng/ml, Gleason score ≤ 4 + 3, stage T2N0M0 and absence of clinically significant disease outside the treatment area. Treatment delivery will be changed in an adaptive iterative manner so as to allow optimisation of the IRE protocol. After focal IRE, men will be followed during 12 months using validated patient reported outcome measures (IPSS, IIEF-15, UCLA-EPIC, EQ-5D, FACT-P, MAX-PC). Early disease control will be evaluated by mpMRI and targeted transperineal biopsy of the treated area at 6 months.

Discussion

The NEAT trial will assess the early functional and disease control outcome of focal IRE using an adaptive design. Our protocol can provide guidance for designing an adaptive trial to assess new surgical technologies in the challenging landscape of health technology assessment in prostate cancer treatment.

Evaluation of 3 T pelvic MRI imaging in prostate cancer patients receiving post-prostatectomy IMRT

PURPOSE

The purpose of the study was to evaluate the utility of a 3 T pelvic magnetic resonance imaging (MRI) in detecting a local recurrence in post-prostatectomy prostate cancer patients prior to receiving adjuvant or salvage intensity-modulated radiation therapy (IMRT).

METHODS

Ninety prostate cancer patients status post-prostatectomy with rising prostate-specific antigen (PSA) had a 3 T pelvic MRI prior to IMRT. The following variables were analyzed for predicting positive findings on MRI: initial presenting and initial post-op PSA, PSA at the time of imaging, PSA velocity, surgical margins, Gleason score, pathological stage, pre-RT digital rectal examination, and type of surgical prostatectomy.

RESULTS

The only significant variable predictive of a positive MRI was positive margins. Specifically, 15 of 46 (33 %) patients with positive margins had a positive MRI, while 5 of 44 (11 %) patients with negative margins had a positive MRI. In the MRI positive group, the location of the positive findings on MRI corresponded with the pathology report in 9 of 12 (75 %) cases.

CONCLUSION

Post-prostatectomy patients with pathologic positive margins are three times more likely to have positive findings on a 3 T MRI.

Metabolic atrophy and 3-T 1H-magnetic resonance spectroscopy correlation after radiation therapy for prostate cancer

OBJECTIVE

To correlate 3-T magnetic resonance spectroscopic imaging (MRSI) with prostate-specific antigen (PSA) levels in patients with prostate cancer treated with external beam radiation therapy to assess the potential advantages of MRSI.

MATERIALS AND METHODS

A total of 50 patients (age range 65-83 years) underwent PSA and MRSI surveillance before and at 3, 6, 12, 18 and 24 months after radiotherapy.

RESULTS

Of the 50 patients examined, 13 patients completely responded to therapy showing metabolic atrophy (MA), defined as a choline-plus-creatine/citrate (CC/C) ratio <0.2, at 3 months; in this group none had biochemical relapse (PSA nadir + 2 ng/mL) by the end of the follow-up. Of the 50 patients, 35 showed a partial response to therapy (CC/C ratio between 0.2 and 0.8) at 3 and 6 months and, of these 35 patients, 30 reached MA at 12 months, while five developed a recurrence (CC/C ratio >0.8). Three of those patients with recurrence had a biochemical relapse at 18 months and the other two at 24 months. Two of the 50 patients did not respond to the treatment, showing persistent disease from the 3rd month (CC/C ratio >0.8); one patient had biochemical relapse at 6 and the other at 12 months.

CONCLUSIONS

MRSI was shown to have a greater potential than PSA level in monitoring patients after radiotherapy, because it anticipates PSA nadir, and biochemical relapse in particular.

Diagnostic imaging work-up for disease relapse after radical treatment for prostate cancer: how to differentiate local from systemic disease? The urologist point of view

About 40% of all patients undergoing radical treatment for localized prostate cancer (PCa) develop biochemical relapse (BCR) during lifetime but only 10-20% of them will show clinically detectable recurrences. Prostatic bed, pelvic or retroperitoneal lymph nodes (LN) and bones (especially the spine) are the sites where we must focus our attention in the early phase of PSA relapse. Time to PSA relapse, PSA kinetics, pathological Gleason score and pathological stage are the main factors related to the likelihood of local vs. distant relapse. Before an extensive diagnostic work-up in patients with BCR, is mandatory to understand if there is a therapeutic consequence or not for the patient. Current imaging techniques have some potential but many limits are yet encountered in the diagnosis of disease relapse. Transrectal ultrasound (TRUS) and Multiparametric Magnetic Resonance Imaging (MRI) have low accuracy in the detection of the recurrence. Today, Choline PET/CT may visualize the site of recurrence earlier, with better accuracy than conventional imaging, in a single step and even in the presence of low PSA level. In recent years, the new radiotracer (18)F-FACBC has been proposed as a possible alternative radiopharmaceutical to detect PCa relapse. From a clinical point of view, first clinical studies showed very promising and reproducible results with an improvement in sensitivity is about 20-25% with respect to Choline PET/CT, rendering the FACBC the possible radiotracer of the future for PCa. In conclusion, many improvements have been recently achieved in imaging techniques for PCa restaging, essentially in Nuclear Medicine and MRI, but negative results remain in many cases. Low sensitivity, costs, availability of technologies and confirmation of the results remain the major limitations in most cases.