Pelvic MRI findings in relapsed prostate cancer after radical prostatectomy

Imaging assessment of prostate cancer recurrence: advances in detection of local and systemic relapse

Prostate cancer (PCa) relapse, defined either by persistent PSA levels (after RP) or biochemical recurrence (BCR), is a common occurrence. The imaging evaluation of patients experiencing PCa relapse has undergone significant advancements in the past decade, notably with the introduction of new Positron Emission Tomography (PET) tracers such as Prostate-specific membrane antigen (PSMA), and the progress in functional Magnetic Resonance Imaging (MRI). This article will explore the role of traditional imaging, the evolution of MRI towards the development of the Prostate Magnetic Resonance Imaging for Local Recurrence Reporting (PI-RR) scoring system, and how next-generation imaging is enhancing diagnostic accuracy in the setting of PCa relapse, which is essential for adopting personalized strategies that may ultimately impact outcomes.

Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography-Based Clinical Target Volume Delineation Guideline for Postprostatectomy Salvage Radiation Therapy: The PERYTON Guideline

PURPOSE

Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) scan is the standard imaging procedure for biochemical recurrent prostate cancer postprostatectomy because of its high detection rate at low serum prostate-specific antigen levels. However, existing guidelines for clinical target volume (CTV) in prostate bed salvage external beam radiation therapy (sEBRT) are primarily based on experience-based clinical consensus and have been validated using conventional imaging modalities. Therefore, this study aimed to optimize CTV definition in sEBRT by using PSMA PET/CT-detected local recurrences (LRs).

METHODS AND MATERIALS

Patients with suspected LR on PSMA PET/CT postprostatectomy were retrospectively enrolled in 9 Dutch centers. Anonymized scans were centrally reviewed by an expert nuclear medicine physician. Each boundary of the CTV guideline from the Groupe Francophone de Radiothérapie en Urologie (GFRU) was evaluated and adapted to improve the accuracy and coverage of the area at risk of LR (CTV) on PSMA PET/CT. The proposed CTV adaptation was discussed with the radiation oncologists of the participating centers, and final consensus was reached. To assess reproducibility, the participating centers were asked to delineate 3 new cases according to the new PERYTON-CTV, and the submitted contours were evaluated using the Dice similarity coefficient (DSC).

RESULTS

After central review, 93 LRs were identified on 83 PSMA PET/CTs. The proposed CTV definition improved the coverage of PSMA PET/CT-detected LRs from 67% to 96% compared with the GFRU-CTV, while reducing the GFRU-CTV by 25%. The new CTV was highly reproducible, with a mean DSC of 0.82 (range, 0.81-0.83).

CONCLUSIONS

This study contributes to the optimization of CTV definition in postprostatectomy sEBRT by using the pattern of LR detected on PSMA PET/CT. The PERYTON-CTV is highly reproducible across the participating centers and ensures coverage of 96% LRs while reducing the GFRU-CTV by 25%.

MRI and PSMA PET/CT of Biochemical Recurrence of Prostate Cancer

Prostate cancer may recur several years after definitive treatment, such as prostatectomy or radiation therapy. A rise in serum prostate-specific antigen (PSA) level is the first sign of disease recurrence, and this is termed biochemical recurrence. Patients with biochemical recurrence have worse survival outcomes. Radiologic localization of recurrent disease helps in directing patient management, which may vary from active surveillance to salvage radiation therapy, androgen-deprivation therapy, or other forms of systemic and local therapy. The likelihood of detecting the site of recurrence increases with higher serum PSA level. MRI provides optimal diagnostic performance for evaluation of the prostatectomy bed. Prostate-specific membrane antigen (PSMA) PET radiotracers currently approved by the U.S. Food and Drug Administration demonstrate physiologic urinary excretion, which can obscure recurrence at the vesicourethral junction. However, MRI and PSMA PET/CT have comparable diagnostic performance for evaluation of local recurrence after external-beam radiation therapy or brachytherapy. PSMA PET/CT outperforms MRI in identifying recurrence involving the lymph nodes and bones. Caveats for use of both PSMA PET/CT and MRI do exist and may cause false-positive or false-negative results. Hence, these techniques have complementary roles and should be interpreted in conjunction with each other, taking the patient history and results of any additional prior imaging studies into account. Novel PSMA agents at various stages of investigation are being developed, and preliminary data show promising results; these agents may revolutionize the landscape of prostate cancer recurrence imaging in the future. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Turkbey in this issue. The slide presentation from the RSNA Annual Meeting is available for this article.

Detecting and Locating the Site of Local Relapse Using 18F-PSMA-1007 Imaging After Primary Treatment of 135 Prostate Cancer Patients-Potential Impact on PSMA-Guided Radiation Therapy

PURPOSE

Due to limited imaging options, the visualization of a local relapse of prostate cancer used to pose a considerable challenge. However, since the integration of ¹⁸F-PSMA-1007-PET/CT into the clinic, a relapsed tumor can now easily be detected by hybrid imaging. The present study aimed to evaluate and map the allocate relapse in a large cohort of prostate cancer patients focusing on individual patient management conclusions for radiation therapy.

PROCEDURES

The current study included 135 men with prostate cancer after primary treatment who underwent ¹⁸F-PSMA-1007-PET/CT due to biochemical relapse detecting a local relapse. Imaging data were reassessed and analyzed with regard to relapse locations. For the correlation of tumor foci with clinical data, we used binary logistic regression models as well as the Kruskal-Wallis test and Mann-Whitney test.

RESULTS

In total, 69.6% of all patients (mean age: 65 years) underwent prostatectomy while 30.4% underwent radiation therapy. PET imaging detected most frequently a unifocal relapse (72.6%). There was a statistically significantly higher rate of ipsilateral cases among the relapsed tumors. Comparing both treatment approaches, tumors relapsed most commonly within the posterior region after surgery and transition/peripheral zone after radiation therapy, respectively.

CONCLUSIONS

The present study confirms that ¹⁸F-PSMA-1007-PET/CT is highly suitable for the localization and allocation of a local relapse in patients with prostate cancer. The data enable further optimizing dose prescriptions and target volume delineations of radiation therapy in the future.

Diagnostic yield of multiparametric MRI for local recurrence at biochemical recurrence after radical prostatectomy

Purpose

To validate the diagnostic yield of multiparametric magnetic resonance imaging (mpMRI) for local biochemical recurrence after radical prostatectomy in patients with biochemical recurrence using large consecutive patient data.

Materials and methods

Of 4632 patients who underwent radical prostatectomy for prostate adenocarcinoma, 748 patients with prostate-specific antigen > 0.2 ng/mL and second confirmatory level were retrospectively identified. Among them, 468 patients who underwent multiparametric magnetic resonance imaging were analyzed. The primary outcome measure was the diagnostic yield of multiparametric magnetic resonance imaging for local recurrence, and the secondary measure was its accuracy, using the response to salvage radiotherapy as reference.

Results

Only 33 patients (7.1%) showed positive imaging findings. The positive and negative predictive values were 84.8% (28/33) and 37.5% (45/120), respectively. The sensitivity and specificity were 27.2% (28/103) and 90% (45/50), respectively. The overall accuracy was 47.7% (73/153). In multivariate logistic regression analysis, prostate-specific antigen level at recurrence was found to be the only factor significantly higher in the positive image findings group.

Conclusions

The universal use of multiparametric magnetic resonance imaging resulted in a low-diagnostic yield for local recurrence in patients with biochemical recurrence after radical prostatectomy. The results suggest that selective use of multiparametric magnetic resonance imaging should be considered in patients with a higher prostate-specific antigen threshold.

Targeting Local Recurrence After Surgery With MRI Imaging for Prostate Cancer in the Setting of Salvage Radiation Therapy

Magnetic resonance imaging (MRI) is being increasingly used for imaging suspected recurrence in prostate cancer therapy. Functional MRI with diffusion and perfusion imaging has the potential to demonstrate local recurrence even at low PSA value. Detection of recurrence can modify the management of postprostatectomy biochemical recurrence. MRI scan acquired before salvage radiotherapy is useful for the localization of recurrent tumors and also in the delineation of the target volume. The objective of this review is to assess the role and potential impact of MRI in targeting local recurrence after surgery for prostate cancer in the setting of salvage radiation therapy.

Imaging assessment of local recurrence of prostate cancer after radical prostatectomy

Definitive therapy for prostate cancer includes radical prostatectomy and radiation therapy. Treatment is elected based on patient preference, biological tumor factors, and underlying health. Post prostatectomy, men are surveyed for disease recurrence with serial PSA measurements, digital rectal exam, and imaging studies depending on nomogram predicted risk of local disease recurrence and distant metastasis. In men with rising PSA levels, pathologically incomplete surgical margins or, if symptoms of metastasis develop, imaging may be obtained to localize disease. In cases of known biochemical recurrence, imaging is used to target biopsy, to contour in salvage radiation therapy and to assess disease response. For local disease recurrence, the most commonly performed exams are pelvic MRI and transrectal US. CT can evaluate for lymph node metastasis, but is suboptimal in the evaluation of the prostatectomy bed. PET/CT and PET/MRI have been used successfully to evaluate for local disease recurrence. The PI-RADSv2.1 manual provides a risk level and lexicon for use in description of prostate carcinoma prior to prostatectomy, but does not address imaging features post-surgery. A detailed description of nodal, bony, and visceral metastasis is given elsewhere. This manuscript outlines the context in which appropriate imaging exams may be obtained and focuses on imaging findings concerning for local disease recurrence after prostatectomy on various imaging modalities including CT, US, MRI, and PET.

Predictors of prostate bed recurrence on magnetic resonance imaging in patients with rising prostate-specific antigen after radical prostatectomy

INTRODUCTION

Radical prostatectomy (RP) is a standard treatment modality for localized prostate cancer. Biochemical failure after RP is usually evaluated with whole-body imaging to exclude distant metastatic disease, and pelvic magnetic resonance imaging (MRI) to detect local recurrence in the prostatectomy bed. The goal of this study is to correlate disease characteristics and demographic data in patients with rising prostate-specific antigen (PSA) after RP to determine association with MRI-detected cancer recurrence.

METHODS

Sixty-four patients who underwent pelvic MRI for rising PSA after RP and had complete clinical and pathological data available were included. Using Chi-squared testing, we analyzed PSA levels, pathological disease characteristics (prostate cancer risk group, Gleason score, extracapsular extension, positive surgical margin, seminal vesicle involvement, perineural invasion, lymphovascular invasion, and PSA level before MRI), time from surgery to biochemical failure, and patient demographic characteristics as potential predictors of MRI-detected local recurrence.

RESULTS

Definite MRI-detected local recurrence was observed in 17/64 patients (27%). Eleven (17%) patients had a suspicious lesion with the differential of scarring, retained seminal vesicle, or recurrent cancer. Thirty-six (56%) patients had no evidence of tumor in the prostate bed or pelvis on MRI. Patient race was associated with likelihood of detecting a prostate nodule on MRI (p=0.04), with African American patients having 82% lower odds of MRI-detected tumor recurrence compared with white patients (p=0.045). No other tumor or patient characteristic was significantly associated with MRI-detected recurrence.

CONCLUSIONS

African American patients with biochemical failure after RP are less likely to have MRI-detectable recurrence in the prostate bed compared with white patients.

Magnetic Resonance Imaging Assessment After Therapy in Prostate Cancer

Prostate cancer is the fifth leading cause of death worldwide. A variety of treatment options is available for localized prostate cancer and may range from active surveillance to focal therapy or whole gland treatment, that is, surgery or radiotherapy. Serum prostate-specific antigen levels are an important tool to monitor treatment success after whole gland treatment, unfortunately prostate-specific antigen is unreliable after focal therapy. Multiparametric magnetic resonance imaging of the prostate is rapidly gaining field in the management of prostate cancer and may play a crucial role in the evaluation of recurrent prostate cancer. This article will focus on postprocedural magnetic resonance imaging after different forms of local therapy in patients with prostate cancer.

Stereotactic radiotherapy for prostate bed recurrence after prostatectomy, a multicentric series

OBJECTIVE

To assess the safety and effectiveness of stereotactic salvage radiotherapy (SSRT) in RT-naïve patients affected by macroscopic prostate bed recurrence.

PATIENTS AND METHODS

Consecutive patients treated for prostate bed macroscopic recurrence in three different Italian institutes were reviewed. Patients were treated with SSRT, with a total dose of 30-40 Gy in five fractions, the mean pre-SSRT PSA level was 2.3 ng/mL. Two different PSA thresholds were defined and biochemical recurrence-free survival (BCRFS) was reported, in order to better express outcome: BCRFS1 (a PSA level increase of >10% compared to the pre-SSRT value) and BCRFS2 (a PSA level increase of >0.2 ng/mL for patients with a PSA nadir of <0.2 ng/mL or two consecutive PSA level increases of >25% compared to nadir in patients with a PSA nadir of <0.2 ng/mL).

RESULTS

In all, 90 patients were treated, with a mean (range) follow-up of 21.2 (2-64) months, and 17 of these patients (19%) had concomitant androgen-deprivation therapy (ADT) during SSRT. Complete biochemical response, defined as a PSA nadir of <0.2 ng/mL, was obtained in 39 of the 90 patients (43.3%). Considering BCRFS1, 25 patients (27.8%) had BCR, with an actuarial median BCRFS1 time of 36.4 months. For BCRFS2, BCR was reported in 32 patients (35.5%), with an actuarial median BCRFS2 time of 24.3 months. There was no Grade >2 toxicity.

CONCLUSIONS

SSRT was found to yield significant biochemical control and allowed ADT delay despite adverse features.

Percutaneous Image-Guided Nodal Biopsy After 11C-Choline PET/CT for Biochemically Recurrent Prostate Cancer: Imaging Predictors of Disease and Clinical Implications

Purpose

Management of recurrent prostate cancer necessitates timely diagnosis and accurate localization of the sites of recurrent disease. The purpose of this study was to assess predictors of histologic outcomes after 11C-choline positron emission tomography/computed tomography (CholPET) to increase the positive predictive value and specificity of CholPET in identifying imaging predictors of malignant and benign nodal disease to better inform clinical decision making regarding local therapy planning.

Materials and Methods

Retrospective review of patients undergoing CholPET followed by percutaneous core needle biopsy between January 1, 2010 and January 1, 2016. A total of 153 patients were identified who underwent 166 biopsy procedures. Patient, CholPET, procedural, and pathologic characteristics were recorded.

Results

A total of 157 biopsies were technically successful, and 110 (70.1%; 95% confidence interval, 62.2-77.1) yielded histologic results abnormal for metastatic prostate cancer. Lesion location, lesion maximum standardized uptake value (SUVmax), SUV ratio (calculated as the ratio of SUVmax to SUV mean in the right atrium), prostate-specific antigen, lesion short axis length, total Gleason score, and castration resistance were all associated with abnormal biopsy results (P values <.001, <.001, <.001, .02, .02, .02, and .015, respectively). External iliac, common iliac, and inguinal sites were associated with much lower rates of histologic positivity (mean [95% confidence interval], 51.2% [35.1-67.1], 46.2% [19.2-74.9], and 33.3% [7.5-70.1]), respectively.

Conclusions

In a cohort of patients in whom core needle biopsy was performed after CholPET, characteristics of choline localization including node location, SUVmax, lesion–to–blood pool SUV ratio, prostate-specific antigen, total Gleason score, and castration resistance were significantly associated with abnormal biopsy results for metastatic disease on CholPET. Relatively high false positive rates were found in common iliac, external iliac, and inguinal lymph node locations. Histologic confirmation of these sites should be strongly considered in the appropriate clinical scenario before designing additional local therapy plans.

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).

Importance of 68Ga-PSMA PET/CT in hospital practice. View of the radiation oncologist

Radiotherapy is a treatment with curative intent, both in patients with primary diagnosis of prostate cancer (PCa) and in patients presenting with biochemical recurrence after radical prostatectomy (RP). Moreover, the use of stereotactic body radiotherapy as a metastasis directed therapy in patients with oligometastatic PCa has significantly increased in the recent years. Conventional imaging techniques, including transrectal ultrasound, computed tomography (CT), morphologic magnetic resonance and bone scintigraphy have traditionally played a minor role in all those clinical scenarios due to its low diagnostic accuracy. The recent development of the positron emission tomography (PET) radiotracer ⁶⁸Ga-PSMA binding to the prostate specific membrane antigen (PSMA), a transmembrane glycoprotein overexpressed in PCa cells, has shown promising results. Detection rates for PCa lesions are higher than CT and higher than the best technique available, the PET/CT with choline. Its superiority has been demonstrated even at very low PSA levels (<1 ng/ml). This increase in diagnostic accuracy represents a potential impact on patient management, especially in radiotherapy. Even if this imaging technique is already available for routine clinical practice in some European countries, in Spain, unfortunately, there is very limited access. In this review, we analyze the main studies that investigate the usefulness of ⁶⁸Ga-PSMA PET/CT in patients with PCa and its potential impact on radiotherapy treatments. In addition, we compared the ⁶⁸Ga-PSMA PET/CT, with the multiparametric magnetic resonance imaging and the PET/CT with choline, in the different clinical scenarios.

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

BACKGROUND

PSMA PET/CT visualises prostate cancer residual disease or recurrence at lower PSA levels compared to conventional imaging and results in a change of treatment in a remarkable high number of patients. Radiotherapy with dose escalation to the former prostate bed has been associated with improved biochemical recurrence-free survival. Thus, it can be hypothesised that PSMA PET/CT-based radiotherapy might improve the prognosis of these patients.

METHODS

One hundred twenty-nine patients underwent PSMA PET/CT due to biochemical persistence (52%) or recurrence (48%) after radical prostatectomy without evidence of distant metastases (February 2014-May 2017) and received PSMA PET/CT-based radiotherapy. Biochemical recurrence free survival (PSA ≤ 0.2 ng/ml) was defined as the study endpoint.

RESULTS

Patients with biochemical persistence were significantly more often high-risk patients with significantly shorter time interval before PSMA PET/CT than patients with biochemical recurrence. Patients with biochemical recurrence had significantly more often no evidence of disease or local recurrence only in PSMA PET/CT, whereas patients with biochemical persistence had significantly more often lymph node involvement. Seventy-three patients were started on antiandrogen therapy prior to radiotherapy due to macroscopic disease in PSMA PET/CT. Cumulatively, 70 (66-70.6) Gy was delivered to local macroscopic tumor, 66 (63-66) Gy to the prostate fossa, 61.6 (53.2-66) Gy to PET-positive lymph nodes and 50.4 (45-52.3) Gy to lymphatic pathways. Median PSA after radiotherapy was 0.07 ng/ml with 74% of patients having a PSA ≤ 0.1 ng/ml. After a median follow-up of 20 months, median PSA was 0.07 ng/ml with ongoing antiandrogen therapy in 30 patients. PET-positive patients without antiandrogen therapy at last follow-up (45 patients) had a median PSA of 0.05 ng/ml with 89% of all patients, 94% of patients with biochemical recurrence and 82% of patients with biochemical persistence having a PSA ≤ 0.2 ng/ml. Post-radiotherapy PSA ≤ 0.1 ng/ml and biochemical recurrence vs. persistence were significantly associated with a PSA ≤ 0.2 ng/ml at last follow-up.

CONCLUSIONS

PSMA PET/CT-based radiotherapy is an effective local salvage treatment option with significant PSA response in patients with biochemical recurrence or persistence after radical prostatectomy leading to deferral of long-term ADT or systemic therapy.

Salvage Radiotherapy for Biochemically Recurrent Prostate Cancer After Prostatectomy

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice. A 67-year-old man had presented to his primary physician for routine health maintenance. A digital rectal examination was performed and revealed a suspicious nodule in the right lobe of the prostate without any extraprostatic extension. A serum prostate-specific antigen (PSA) test was 12.4 ng/mL. He had no previous PSA tests. Transrectal ultrasound-guided prostate biopsy showed Gleason 3 + 4 prostate adenocarcinoma in seven of 12 cores. Bone scan and computed tomography scan of the pelvis showed no evidence of metastatic disease, and the patient underwent a robotic-assisted radical prostatectomy with bilateral pelvic lymphadenectomy. Pathology revealed Gleason 3 + 4 adenocarcinoma bilaterally, with extracapsular extension, no seminal vesicle invasion, a 2-mm positive margin at the right mid gland, and 0 of 15 lymph nodes containing adenocarcinoma. Two months after surgery, he had mild stress urinary incontinence and PSA of < 0.1 ng/mL. Adjuvant radiotherapy was discussed, but he elected to have careful follow-up. His PSA was monitored every 6 months and gradually increased from < 0.1 ng/mL to 0.4 ng/mL over the next 3 years. He was asymptomatic. He was referred to discuss the role of salvage radiotherapy.

Detection level and pattern of positive lesions using PSMA PET/CT for staging prior to radiation therapy

Background

To determine the potential role of ⁶⁸Ga-PSMA positron emission tomography/computed tomography (PET/CT) in radiotherapy (RT) planning for prostate cancer (PCa).

Methods

One hundred twenty-nine patients (pts) with ⁶⁸Ga-PSMA PET/CT were retrospectively analysed. Potentially influencing factors (androgen deprivation therapy, amount of ⁶⁸Ga-PSMA-HBED-CC, PSA doubling time ≤/> 10 months, PSA before PET/CT, T−/N-category and Gleason score) were evaluated by logistic regression analysis. The detection rate of PSMA PET/CT was compared to contrast enhanced CT and its impact on RT management analysed.

Results

One hundred twenty-nine patients (pts) (20 at initial diagnosis, 49 with PSA relapse and 60 with PSA persistence after radical prostatectomy) received PSMA PET/CT prior to RT. The majority of pts. (71.3%) had PET-positive findings (55.1% of pts. with PSA recurrence, 75% of pts. with PSA persistence and 100% of newly diagnosed pts). Median PSA before PET/CT in pts. with pathological findings (n = 92) was 1.90 ng/ml and without (n = 37) 0.30 ng/ml. PSA level at time of PET/CT was the only factor associated with PET-positivity. In pts. with a PSA ≤ 0.2 ng/ml, the detection rate of any lesion was 33.3%, with a PSA of 0.21–0.5 ng/ml 41.2% and with a PSA of 0.51–1.0 ng/ml 69.2%, respectively. Regarding the anatomic distribution of lesions, 42.2% and 14.7% of pts. with relapse or persistence had pelvic lymph node and distant metastases. In pts. at initial diagnosis the detection rate of pelvic lymph nodes and distant metastases was 20% and 10%. ⁶⁸Ga-PSMA PET/CT had a high detection rate of PCa recurrence outside the prostatic fossa in pts. being considered for salvage RT (22.4% PET-positive pelvic lymph nodes and 4.1% distant metastases). Compared to CT, PSMA PET/CT had a significantly higher sensitivity in diagnosing rates of local recurrence/primary tumour (10.1% vs. 38%), lymph nodes (15.5% vs. 38.8%) and distant metastases (5.4% vs. 14.0%). This resulted in a modification of RT treatment in 56.6% of pts.

Conclusions

The detection of PCa is strongly associated with PSA level at time of ⁶⁸Ga-PSMA PET/CT. PSMA PET/CT differentiates between local, regional and distant metastatic disease with implications for disease management. PSMA PET/CT allows for tumour detection in post-prostatectomy pts. with PSA ≤ 0.5 ng/ml considered for salvage RT.

Magnetic resonance imaging for prostate cancer before radical and salvage radiotherapy: What radiation oncologists need to know

External beam radiotherapy (EBRT) is one of the principal curative treatments for patients with prostate cancer (PCa). Risk group classification is based on prostate-specific antigen (PSA) level, Gleason score, and T-stage. After risk group determination, the treatment volume and dose are defined and androgen deprivation therapy is prescribed, if appropriate. Traditionally, imaging has played only a minor role in T-staging due to the low diagnostic accuracy of conventional imaging strategies such as transrectal ultrasound, computed tomography, and morphologic magnetic resonance imaging (MRI). As a result, a notable percentage of tumours are understaged, leading to inappropriate and imprecise EBRT. The development of multiparametric MRI (mpMRI), an imaging technique that combines morphologic studies with functional diffusion-weighted sequences and dynamic contrast-enhanced imaging, has revolutionized the diagnosis and management of PCa. As a result, mpMRI is now used in staging PCa prior to EBRT, with possible implications for both risk group classification and treatment decision-making for EBRT. mpMRI is also being used in salvage radiotherapy (SRT), the treatment of choice for patients who develop biochemical recurrence after radical prostatectomy. In the clinical context of biochemical relapse, it is essential to accurately determine the site of recurrence - pelvic (local, nodal, or bone) or distant - in order to select the optimal therapeutic management approach. Studies have demonstrated the value of mpMRI in detecting local recurrences - even in patients with low PSA levels (0.3-0.5 ng/mL) - and in diagnosing bone and nodal metastasis. The main objective of this review is to update the role of mpMRI prior to radical EBRT or SRT. We also consider future directions for the use and development of MRI in the field of radiation oncology.

Delineation of the Prostate Bed: The "Invisible Target" Is Still an Issue?

For pathological high-risk prostate cancer, adjuvant irradiation has shown a survival benefit. Phase III studies have highlighted that half men would face biochemical relapse and would be candidate for radiotherapy at adjuvant or salvage times. Despite at least four published international contouring guidelines from different collaborative groups, discrepancies remain for volumes, delineation, and margins to be considered in order to optimize radiotherapy planning. This article from “Groupe d’Etude des Tumeurs UroGénitales (GETUG)” members will focus on controversies to help clinicians to create best volume delineation for adjuvant or salvage post prostatectomy radiotherapy.

Evaluation of tumor recurrences after radical prostatectomy using 18F-Choline PET/CT and 3T multiparametric MRI without endorectal coil: a single center experience

BACKGROUND

To evaluate and compare the utility of 18F-fluorocholine (18F-CH) PET/CT versus 3-Tesla multiparametric MRI (mpMRI) without endorectal coil to detect tumor recurrences in patients with biochemical relapse following radical prostatectomy (RP). Secondarily, to identify possible prognostic variables associated with mpMRI and 18F-CH PET/CT findings.

METHODS

Retrospective study of 38 patients who developed biochemical recurrence after RP between the years 2011 and 2015 at our institution. PET/CT and mpMRI were both performed within 30 days of each other in all patients. The PET/CT was reviewed by a nuclear medicine specialist while the mpMRI was assessed by a radiologist, both of whom were blinded to outcomes.

RESULTS

The median prostate-specific antigen (PSA) value pre-MRI/PET-CT was 0.9 ng/mL (interquartile range 0.4-2.2 ng/mL). There were no differences in the detection rate between 18F-CH PET/CT and mpMRI for local recurrence (LR), lymph node recurrence (LNR) and bone metastases (BM). Separately, mpMRI and 18F-CH PET/CT were positive for recurrence in 55.2% and 52.6% of cases, respectively, and in 65.7% of cases when findings from both modalities were considered together. The detection of LR was better with combined mpMRI and choline PET/CT versus choline PET/CT alone (34.2% vs 18.4%, p = 0.04). Salvage treatment was modified in 22 patients (57.8%) based on the imaging findings. PSA values on the day of biochemical failure were significantly associated with mpMRI positivity (adjusted odds ratio (OR): 30.9; 95% confidence interval (CI): 1.5-635.8). Gleason score > 7 was significantly associated with PET/CT positivity (OR: 13.9; 95% CI: 1.5-125.6). A significant association was found between PSA doubling time (PSADT) (OR: 1.3; 95% CI: 1.0-1.7), T stage (OR: 21.1; 95% CI: 1.6-272.1), and LR.

CONCLUSIONS

Multiparametric MRI and 18F-CH PET/CT yield similar detection rates for LR, LNR and pelvic BM. The combination of both imaging techniques provides a better LR detection versus choline PET/CT alone. The initially planned salvage treatment was modified in 57.8% of patients due to imaging findings. In addition to PSA values, Gleason score, T stage, and PSADT may provide valuable data to identify those patients that are most likely to benefit from undergoing both imaging procedures.

Localizing sites of disease in patients with rising serum prostate-specific antigen up to 1ng/ml following prostatectomy: How much information can conventional imaging provide?

PURPOSE

Accurate identification of the source of a detectable serum prostate-specific antigen (PSA) in the postprostatectomy setting is a major challenge among the urologic community. The aim of this study was to assess positivity rates of imaging examinations performed in patients with early PSA rise after prostatectomy and to summarize the management strategies adopted in this clinical scenario.

METHODS

Institutional Review Board-approved retrospective study of 142 postprostatectomy patients with PSA rise up to 1ng/ml who underwent evaluation with combination of multiparametric pelvic magnetic resonance imaging (MRI)±whole-body or bone MRI, bone scintigraphy, computed tomography (CT) chest-abdomen-pelvis, ¹⁸F-fludeoxyglucose-positron emission tomography (PET)/CT or ¹⁸F-sodium fluoride-PET/CT at a single tertiary cancer center. Imaging results were summarized per modality and compared with pathology findings.

RESULTS

Pelvic MRI was positive in 15/142 (11%) patients (14 patients with local recurrence in the surgical bed and 1 patient with pelvic osseous metastases). Of these 15, 10 patients underwent additional imaging examinations; none revealed positive findings. Of the 127 patients with negative pelvic MRI, 54 (43%) underwent additional imaging examinations; only 1/54 had positive findings (false-positive T8 lesion on bone scintigraphy and FDG-PET/CT; biopsy was negative for cancer). Overall, 12/16 patients with positive imaging findings and 75/126 (60%) patients with negative imaging received treatment (radiation, hormones or chemotherapy).

CONCLUSION

The conventional imaging identified sites of disease, almost always in the form of local recurrence, in a minority of patients with early PSA rise postprostatectomy.