Prostatic cryosurgery: use of MR imaging in evaluation of success and technical modifications

Time-course changes in multiparametric magnetic resonance imaging following focal cryotherapy for localized prostate cancer: Initial experience

PURPOSE

To evaluate the time-course changes of multiparametric MRI findings following focal cryotherapy for localized prostate cancer.

METHODS

Sixteen patients who underwent focal cryotherapy as an initial curative treatment for localized prostate cancer during March 2017-April 2021 were included. Before the treatment, the patients underwent targeted prostate biopsy using MRI-transrectal ultrasound fusion. Overall, 64 MRIs were conducted after focal cryotherapy and the temporal post-treatment MR signal changes of the ablated area in T2WI, T1WI, DWI, and DCE-MRI were analyzed.

RESULTS

Technical success was achieved in all patients. The median follow-up period was 22 months. The initial post-treatment MRI revealed significant signal changes in the target lesions for all patients, including the disappearance of findings suggestive of cancer. At 3 months post-treatment, most lesions were hyperintense with a hypointense rim on T2WI, T1WI, and DWI (83.3 %). After 6 months, hyperintensity reduced, and after 17 months, all lesions showed hypointensity in these sequences. DCE-MRI of most patients showed loss of internal enhancement; however, one patient exhibited residual nodular enhancement in the ablated area at 3 months, which disappeared after 6 months. Peripheral enhancement was common at 3 months, disappearing after 23 months. Two patients showed biopsy-evidenced local recurrence. The recurrent lesions showed hypointensity on T2WI with diffusion restriction and early contrast enhancement in the ventral transition zone.

CONCLUSION

MRI findings of the ablated sites following focal cryotherapy for localized prostate cancer show dynamic signal changes, especially within the first 6 months.

First experiences and results after cryoablation of prostate cancer with histopathological evaluation and imaging-based follow-up

Aim: To share our experience after 28 cryoablation treatments for prostate cancer (PCa) with histopathology, clinical data and MRI as the follow-up methods. Methods: Clinical follow-up comprised prostate specific antigen (PSA)-measurements, PSA-density and quality-of-life-parameters. multi-parametric (mp)MRI pre- and post-cryoablation were retrospectively re-analyzed in 23 cases using Likert scores. Follow-up-histopathology was performed via MRI/ultrasound fusion-guided and/or systematic biopsy. Receiver operating characteristic curve analysis was performed. Results: 17 PCa (61%) were diagnosed within 12-month post-cryotherapy (infield and out-of-field disease). PSA levels and PSA density were not significantly different between patients with or without PCa recurrence. mpMRI can characterize the decrease in prostate volume and necrosis. Area under the curve for the detection of PCa was 81% (global Likert scores), 74-87% (T2), 78% (diffusion weighted imaging) and 57-78% (dynamic contrast enhanced imaging; Youden-selected cutoff ≥3). Conclusion: Besides histopathological evaluation and control biopsy, MRI might have the potential to accurately detect PCa after cryotherapy. Clinical data and interdisciplinary communication are required for efficient monitoring after cryoablation treatments for PCa.

Acute and subacute prostate MRI findings after MRI-guided transurethral ultrasound ablation of prostate cancer

BACKGROUND

Magnetic resonance imaging (MRI)-guided transurethral ultrasound ablation (TULSA) is an emerging method for treatment of localized prostate cancer (PCa). TULSA-related subacute MRI findings have not been previously characterized.

PURPOSE

To evaluate acute and subacute MRI findings after TULSA treatment in a treat-and-resect setting.

MATERIAL AND METHODS

Six men with newly diagnosed MRI-visible and biopsy-concordant clinically significant PCa were enrolled and completed the study. Eight lesions classified as PI-RADS 3-5 were focally ablated using TULSA. One- and three-week follow-up MRI scans were performed between TULSA and robot-assisted laparoscopic prostatectomy.

RESULTS

TULSA-related hemorrhage was detected as a subtle T1 hyperintensity and more apparent T2 hypointensity in the MRI. Both prostate volume and non-perfused volume (NPV) markedly increased after TULSA at one week and three weeks after treatment, respectively. Lesion apparent diffusion coefficient values increased one week after treatment and decreased nearing the baseline values at the three-week MRI follow-up.

CONCLUSION

The optimal timing of MRI follow-up seems to be at the earliest at three weeks after treatment, when the post-procedural edema has decreased and the NPV has matured. Diffusion-weighted imaging has little or no added diagnostic value in the subacute setting.

Interpretation and reporting multiparametric prostate MRI: a primer for residents and novices

Multiparametric MRI has developed as a tool for prostate cancer lesion detection, characterization, staging, surveillance, and imaging of local recurrence. Given the disease frequency and the growing importance of imaging, as reliance on PSA declines, radiologists involved in prostate MRI imaging must become proficient with the fundamentals of multiparametric prostate MRI (T2WI, DWI, DCE-MRI, and MR spectroscopy). Interpretation and reporting must yield accuracy, consistency, and add value to clinical care. This review provides a primer to novices and trainees learning about multiparametric prostate MRI. MRI technique is presented along with the use of particular MRI sequences. Relevant prostate anatomy is outlined and imaging features of prostate cancer with staging are discussed. Finally structured reporting is introduced, and some limitations of prostate MRI are discussed.

Multiparametric magnetic resonance imaging in the management and diagnosis of prostate cancer: current applications and strategies

Magnetic resonance imaging (MRI) has become increasingly used worldwide in the diagnosis and management of prostate cancer. With advances in multiparametric MRI (mpMRI) technology, such as the use of dynamic contrast-enhanced and diffusion-weighted imaging sequences, observational studies have evaluated the utility for mpMRI in the continuum of prostate cancer management, from improving the detection of clinically significant prostate cancer, to planning radical prostatectomy and radiation therapy and the early detection of local recurrence. Furthermore, the potential for advanced imaging to reduce the burden of routine serial prostate needle biopsies for men on active surveillance is a promising area of research. MRI technology continues to evolve, and the potential applications in the management of prostate cancer care will require well-designed multi-institutional prospective clinical trials and rigorous efforts to standardize reporting and improve dissemination of expertise across institutions.

Dynamic contrast-enhanced MR evaluation of prostate cancer before and after endorectal high-intensity focused ultrasound

PURPOSE

The authors sought to determine the diagnostic performance of dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging in the evaluation of prostate cancer before and after transrectal high-intensity focused ultrasound (HIFU) treatment.

MATERIALS AND METHODS

We analysed 25 patients with prostate cancer. The prostate-specific antigen (PSA) value was evaluated 1, 4 and 6 months after treatment. DCE-MR imaging was performed the day prior to and 1, 4 and 6 months after HIFU treatment. Transrectal prostate biopsies were obtained at the time of diagnosis and 6 months after treatment.

RESULTS

Before treatment, intraglandular lesions were considered to be potential sites of neoplasm and subsequently confirmed as sites of prostate adenocarcinoma in all 25 patients based on prostatespecific antigen (PSA) values and histological examinations (rho=1; p<0.001). Using histology as the gold standard, DCE-MR imaging displayed 100% sensitivity, 100% specificity, 100% positive predictive value and 100% negative predictive value before treatment. After HIFU treatment, DCE-MR imaging showed 100% sensitivity and 96% specificity.

CONCLUSIONS

DCE-MR imaging can be used to visualise prostate adenocarcinoma. Several morphological and postgadolinium modifications in the follow-up DCE-MR images after HIFU treatment were also observed.

Robotic prostate biopsy and its relevance to focal therapy of prostate cancer

Focal therapy is an individualized treatment option for prostate cancer, which destroys localized cancerous tissue but not normal tissue, thus avoiding the morbidities associated with whole-gland therapy. Accurate cancer localization and precise ablation are integral to the success of focal therapy, which remains unproven owing to suboptimal patient selection. Currently, there are no clinical or biopsy features that can identify unifocal prostate cancer and no imaging modality that can accurately diagnose or localize prostate cancer. MRI diagnosis has the best accuracy but high cost and limited access hinder its widespread adoption. New management options, including focal therapy and active surveillance, require prostate biopsy to detect, localize and characterize the cancer. Transrectal prostate biopsy has a high false-negative detection rate, which might be related to an inability to biopsy the anterior and apical part of the prostate or interoperator variation. Transrectal biopsy is also associated with sepsis and bleeding. Robotic transperineal prostate biopsy can overcome the limitations of transrectal procedures. Robotic biopsy is automated with high accuracy, has improved access to the apex and anterior part of the prostate and has low risk of sepsis. Furthermore, it involves only two skin punctures, compared with template-based transperineal prostate biopsy, which can result in multiple wounds. Robotic prostate biopsy fulfills the fundamental needs of focal therapy and might be the platform for future treatment delivery for prostate cancer.

High-frequency microwave ablation method for enhanced cancer treatment with minimized collateral damage

To overcome the limits of conventional microwave ablation, a new frequency spectrum above 6 GHz has been explored for low-power and low collateral damage ablation procedure. A planar coaxial probe-based applicator, suitable for easy insertion into the human body, was developed for our study to cover a wideband frequency up to 30 GHz. Thermal ablations with small input power (1-3 W) at various microwave frequencies were performed on nude mice xenografted with human breast cancer. Comparative study of ablation efficiencies revealed that 18-GHz microwave results in the largest difference in the temperature rise between cancer and normal tissues as well as the highest ablation efficiency, reaching 20 times that of 2 GHz. Thermal profile study on the composite region of cancer and fat also showed significantly reduced collateral damage using 18 GHz. Application of low-power (1 W) 18-GHz microwave on the nude mice xenografted with human breast cancer cells resulted in recurrence-free treatment. The proposed microwave ablation method can be a very effective process to treat small-sized tumor with minimized invasiveness and collateral damages.

Role of MRI in follow-up after focal therapy for prostate carcinoma

OBJECTIVE

In patients with clinically suspected local recurrence of prostate cancer, a lobulated hyperintense mass in the radical prostatectomy fossa can be readily visualized with T2-weighted MRI, but this imaging technique is less successful after treatments such as radiation therapy, high-intensity focused ultrasound, and cryosurgery. We describe the additional value of functional techniques in the assessment of local recurrence.

CONCLUSION

The use of functional MRI techniques such as MR spectroscopy, diffusion-weighted imaging, and dynamic contrast-enhanced MRI has shown promise in increasing overall imaging performance in the detection of local recurrence.

MRI-guided cryoablation: In vivo assessment of focal canine prostate cryolesions

PURPOSE

To analyze the appearance of acute and chronic canine prostate cryolesions on T1-weighted (T1w) and T2-weighted (T2w) magnetic resonance imaging (MRI) and compare them with contrast-enhanced (CE) MRI and histology for a variety of freezing protocols.

MATERIALS AND METHODS

Three different freezing protocols were used in canine prostate cryoablation experiments. Six acute and seven chronic (survival times ranging between 4-53 days) experiments were performed. The change in T2w signal intensity was correlated with freezing protocol parameters. The lesion area on T2w MRI was compared to CE-MRI. Histopathologic evaluation of the cryolesions was performed and visually compared to the appearance on MRI.

RESULTS

The T2w signal increased from pre- to postfreeze at the site of the cryolesion, and the enhancement was higher for smaller freeze area and duration. The T2w lesion area was between the CE nonperfused area and the hyperenhancing CE rim. The appearance of the lesion on T1w and T2w imaging over time correlated with outcome on pathology.

CONCLUSION

T1w and T2w MRI can potentially be used to assess cryolesions and to monitor tissue response over time following cryoablation.

MR imaging-guided percutaneous cryoablation of the prostate in an animal model: in vivo imaging of cryoablation-induced tissue necrosis with immediate histopathologic correlation

PURPOSE

To evaluate the feasibility of magnetic resonance (MR) imaging-guided percutaneous cryoablation of normal canine prostates and to identify MR imaging features that accurately predict the area of tissue damage at a microscopic level.

MATERIALS AND METHODS

Six adult male mixed-breed dogs were anesthetized, intubated, and placed in a 0.5-T open MR imaging system. A receive-only endorectal coil was placed, and prostate location and depth were determined on T1-weighted fast spin-echo (FSE) MR imaging. After placement of cryoprobes and temperature sensors, three freezing protocols were used to ablate prostate tissue. Ice ball formation was monitored with T1-weighted FSE imaging. Tissue necrosis area was assessed with contrast-enhanced weighted MR imaging and compared with histopathologic findings.

RESULTS

A total of 12 cryolesions (mean size, 1.2 cm) were bilaterally created in six prostates. Ice ball formation was oval and signal-free on T1-weighted FSE sequences in all cases. Postprocedural contrast-enhanced MR imaging typically showed a nonenhancing area of low signal intensity centrally located within the frozen area, surrounded by a bright enhancing rim in all cases. On histopathologic examination, two distinct zones were identified within cryolesions. Centrally, a necrotic zone with complete cellular destruction and hemorrhage was found. Between this necrotic zone and normal glandular tissue, a zone of fragmented and intact glands, interstitial edema, and rare acute inflammatory cells was seen. Correlation between nonenhancement on contrast-enhanced weighted MR images and tissue necrosis on pathologic examination was consistent within all six dogs.

CONCLUSIONS

MR imaging-guided cryoablation of the prostate is technically feasible. The nonenhancing area on postablation contrast-enhanced weighted MR imaging accurately predicts the area of cryoablation-induced tissue necrosis on pathologic analysis.

Prostate cryotherapy monitoring using vibroacoustography: preliminary results of an ex vivo study and technical feasibility

The objective of this research is to prospectively evaluate the feasibility of vibroacoustography (VA) imaging in monitoring prostate cryotherapy in an ex vivo model. Baseline scanning of an excised human prostate is accomplished by a VA system apparatus in a tank of degassed water. Alcohol and dry ice mixture are used to freeze two prostate tissue samples. The frozen prostates are subsequently placed within the water tank at 27 degrees C and rescanned. VA images were acquired at prescribed time intervals to characterize the acoustic properties of the partially frozen tissue. The frozen prostate tissue appears in the images as hypoemitting signal. Once the tissue thaws, previously frozen regions show coarser texture than prior to freezing. The margin of the frozen tissue is delineated with a well-defined rim. The thawed cryolesions show a different contrast compared with normal unfrozen prostate. In conclusion, this pilot study shows that VA produces clear images of a frozen prostate at different temperature stages. The frozen tissue appears as a uniform region with well-defined borders that are readily identified. These characteristic images should allow safer and more efficient application of prostatic cryosurgery. These results provide substantial motivation to further investigate VA as a potential modality to monitor prostate cryotherapy intraoperatively.

Prostate Cancer: Gadolinium-enhanced MR Imaging at 3 Weeks Compared with Needle Biopsy at 6 Months after Cryoablation

PURPOSE

To determine if nonenhancing tissue on gadolinium-enhanced magnetic resonance (MR) images obtained 3 weeks after cryoablation of the prostate helps reliably and accurately predict nonviable cryoablated tissue at 6-month biopsy.

MATERIALS AND METHODS

Fifty-four consecutive patients with prostate cancer who underwent cryoablation were followed up prospectively. Fifty-one underwent gadolinium-enhanced MR imaging at 3 weeks (three had gadolinium allergy); 49, biopsy at 6 months (three refused and two had other primary malignancies); and all, prostate-specific antigen (PSA) tests at 6 weeks, 3 months, and every 3 months thereafter. MR images were evaluated and scored according to the degree of signal void and were correlated with the 6-month biopsy reports and, to a lesser degree, PSA levels. The biopsy reports were examined for the presence or absence of cancerous tissue, viable tissue, and nonviable tissue. A one-way analysis of variance was used for statistical and regression analyses.

RESULTS

The correlation of MR imaging scores with PSA levels and MR imaging scores with biopsy findings resulted in P values of.337 and.780, respectively. A slight statistically significant trend existed for the relation of biopsy results with PSA levels, with a P value of.041, which was expected.

CONCLUSION

Findings of postoperative gadolinium-enhanced MR imaging are not predictive of 6-month biopsy results or follow-up PSA levels.

Diffusion-weighted MRI after cryosurgery of the canine prostate. Magnetic resonance imaging

PURPOSE

To evaluate the acute lesion created by cryosurgery with diffusion-weighted magnetic resonance imaging (DWI).

MATERIALS AND METHODS

The appearance of the acute cryolesion was evaluated in four canine prostates DWI after they were warmed to original body temperature. The prostates were excised, stained with triphenyl tetrazolium chloride (TTC), photographed, prepared for hematoxylin and eosin (H&E) staining, and examined under a light microscope.

RESULTS

A marked decrease in apparent diffusion coefficient of 38% was evident in the center of the previously frozen tissue, but not in all of the previously frozen tissue. Histologic results confirm differences between the iceball core and the periphery of the iceball, which have markedly different imaging characteristics on DWI.

CONCLUSION

The core of the previously frozen tissue has a reduced apparent diffusion coefficient (ADC) compared to the periphery of the previously frozen tissue and previously unfrozen tissue.

The evolution and state of modern technology for prostate cryosurgery

Cryosurgery is the in situ ablation of a target tissue by application of extreme cold temperature. The ability of cryosurgery to ablate tissue is unquestioned. It is the controlled application of a cryoinjury in a manner to minimize morbidity that is problematic. Prostate cryosurgery is complicated by the proximity of the prostate to adjacent structures that are sensitive to a freeze injury, namely the urethra, rectal wall, and neurovascular bundles. Several recent technological advances have led to the development of an effective treatment protocol with acceptable morbidity. These include the advent of real-time transrectal ultrasound, cryomachines with almost instant freeze-thaw control through the use of the Joule-Thompson effect, and warming catheters to effectively preserve the integrity of the urethra and external sphincter. Further, temperature monitoring at the posterior margin of the prostate sometimes combined with an injection of saline solution into Denonvilliers fascia has reduced the occurrence of urethrorectal fistula formation to 0% to 0.5% in modern series. We review the key innovations of prostate cryosurgery that differentiate this state-of-the-art procedure from that used by early investigators to even that of the early 1990s. Potential future innovations, specifically related to image guidance of the procedure, are also addressed.

Cryosurgery for prostate cancer: new technology and indications

Patients diagnosed with prostate cancer who elect to pursue active treatment of their disease must choose among the many available treatment alternatives. Several treatment options now exist for similar-stage disease (clinical T1-3N0M0), including radical prostatectomy, external beam radiation, prostate brachytherapy (PB), and cryosurgical ablation of the prostate (CSAP). This article reviews the current role of CSAP in the treatment of clinically localized prostate cancer. CSAP has a role in the primary treatment of men with high-risk, clinically localized prostate cancer (defined as PSA >10, Gleason score >or=7, or clinical stage >or= cT2B). CSAP (occasionally followed by external beam radiotherapy) appears to offer improved rates of cancer control over other types of single or combination therapies for this high-risk prostate cancer, and it is associated with an acceptable side-effect profile. CSAP should also be the treatment of choice for men with recurrent local disease who have undergone external beam radiotherapy or PB.

Outcome and safety of transrectal US-guided percutaneous cryotherapy for localized prostate cancer

OBJECTIVES

To assess the effectiveness and safety of ultrasound (US)-guided cryotherapy as a primary treatment for localized prostate cancer.

MATERIALS AND METHODS

A prospective study of percutaneous transrectal US (TRUS)-guided cryotherapy was performed on 71 patients with T1-T3, N0, M0 prostatic cancer: 10 patients underwent two or more procedures. All cases were newly diagnosed and patients had no previous treatment for cancer. For all patients, TRUS biopsies were performed at 5-6 months. Patients were monitored at 6 weeks; 3, 6, 9, and 12 months; and twice yearly thereafter for prostate specific antigen (PSA) levels, complications, and clinical evidence of residual disease.

RESULTS

Follow-up from 10 to 36 months was available for 70 of 71 patients; one patient died of unrelated disease. Initially, 10 of 69 patients had positive postcryotherapy biopsy results. After repeated treatment, nine of these 10 patients had negative biopsy results and one patient had no follow-up. Overall, 68 of 69 patients had negative biopsy results. At 1 year, 43 of 64 (67%) had an undetectable PSA level. Two patients had proven metastases. Complications include three cases with urethral sloughing requiring transurethral resection of the prostate (TURP). One patient had orchitis. Two patients had persistent incontinence, one as the result of a TURP. There was no death, acute serious morbidity, or fistula formation. Impotence was universal at 6 months, but many patients demonstrated late recovery.

CONCLUSION

Cryoablation is an imaging-guided percutaneous intervention for prostate cancer that can safely yield disease-free status in a high percentage of patients with localized disease.

Open-configuration MR imaging, intervention, and surgery of the urinary tract

The open-configuration MR imaging system provides new applications both in diagnosis and in therapy of conditions in the urinary tract. In addition to conventional imaging, the open configuration permits MR imaging of patients in many positions. This has already been shown to be useful in imaging the pelvis during voiding, where a sitting position allows urodynamic evaluation. The lithotomy position can be used for imaging the prostate, which also permits procedural access. The ultimate purpose of the interventional MR imaging suite is to integrate therapeutic tools and techniques with MR imaging. From surgical planning through specialized imaging systems with minimally invasive surgical applications, new methods are being developed and implemented. This new field of image-guided therapy will require extensive clinical development and evaluation for applications in the urinary tract. This will require a large concentrated interdisciplinary effort of surgeons, radiologists, computer scientists, engineers, and physicists. Successful integration of basic research and clinical work will result in a number of cutting-edge technologies with direct clinical application in the urinary tract. Initial projects have included biopsies, endoscopies, and real-time procedural control of high-temperature and cryogenic ablations. It is anticipated that the current surge in image-guided interventions will motivate even more research activity in this field, and will ultimately define the role of MR imaging guidance in urologic intervention and surgery.