MRI-guided focal therapy of prostate cancer

[MRI-guided minimally invasive treatment of prostate cancer]

CLINICAL/METHODOLOGICAL ISSUE

Multiparametric magnetic resonance imaging (mpMRI) of the prostate plays a crucial role in the diagnosis and local staging of primary prostate cancer.

STANDARD RADIOLOGICAL METHODS

Image-guided biopsy techniques such as MRI-ultrasound fusion not only allow guidance for targeted tissue sampling of index lesions for diagnostic confirmation, but also improve the detection of clinically significant prostate cancer.

METHODOLOGICAL INNOVATIONS

Minimally invasive, focal therapies of localized prostate cancer complement the treatment spectrum, especially for low- and intermediate-risk patients.

PERFORMANCE

In patients of low and intermediate risk, MR-guided, minimally invasive therapies could enable local tumor control, improved functional outcomes and possible subsequent therapy escalation. Further study results related to multimodal approaches and the application of artificial intelligence (AI) by machine and deep learning algorithms will help to leverage the full potential of focal therapies for prostate cancer in the upcoming era of precision medicine.

ACHIEVEMENTS

Completion of ongoing randomized trials comparing each minimally invasive therapy approach with established whole-gland procedures is needed before minimally invasive therapies can be implemented into existing treatment guidelines.

PRACTICAL RECOMMENDATIONS

This review article highlights minimally invasive therapies of prostate cancer and the key role of mpMRI for planning and conducting these therapies.

MRI-guided focal laser ablation of prostate cancer: a prospective single-arm, single-center trial with 3 years of follow-up

PURPOSE

We aimed to assess post-interventional and 36-month follow-up results of a single-center, single-arm, in-bore phase I trial of focal laser ablation (FLA) guided by multiparametric magnetic resonance imaging (mpMRI).

METHODS

FLA procedures were done in-bore MRI using a transperineal approach. Primary endpoints were feasibility and safety expressed as lack of grade 3 complications. Secondary endpoints were changes in international prostate symptom score (IPSS), sexual health inventory for men (SHIM), quality of life (QoL) scores, and serum prostate specific antigen (PSA) levels. Treatment outcomes were assessed by combined mpMRI-ultrasound fusion-guided and extended sextant systematic biopsy after 12, 24, and optionally after 36 months.

RESULTS

Fifteen participants were included. Seven patients (46.67%) had Gleason 3+3 and 8 patients (53.33%) had Gleason 3+4 cancer. All patients tolerated the procedure well, and no grade 3/4 complications occurred. All grade 1 and 2 complications were transient and resolved completely. There was no significant change in mean IPSS from baseline (-1, p = 0.460) and QoL (0, p = 0.441) scores following FLA but there was a significant drop in mean SHIM scores (-2, p = 0.010) compared to pretreatment baselines. Mean PSA significantly decreased after FLA (-2.5, p < 0.001). Seven out of 15 patients (46.67%) had residual cancer in, adjacent, or in close proximity to the treatment area (1 × 4+3=7, 1 × 3+4=7, and 5 × 3+3=6). Four out of 15 patients (26.67%) underwent salvage therapy (2 repeat FLA, 2 radical prostatectomy).

CONCLUSION

After 3 years of follow-up we conclude focal laser ablation is safe and feasible without significant complications.

A preliminary comparative study of percutaneous CT-guided cryoablation with surgical resection for osteoid osteoma

Background

The traditional treatment for osteoid osteoma is the nidus’ surgical resection, which was difficult to eradicate with more invasive and complications because of osteosclerosis surrounding the nidus. This study aimed to analyze the efficacy and safety of percutaneous CT-guided cryoablation of osteoid osteoma at different sites (especially refractory sites such as the spine).

Methods

Fifteen patients with osteoid osteoma who underwent cryoablation at our institution were analyzed retrospectively on their imaging data and clinical visual analog scale (VAS) pain scores before and after the procedure. Fifty-three patients underwent surgical resection during the period were also included in this study as a control group. Treatment efficacy was assessed primarily by comparing the differences in VAS scores at different time points in each group of patients by paired-sample t-test. Differences in length of hospital stay and complications between the two groups were also compared.

Results

The technical success rate was 100% in both the cryoablation and surgical resection group. Cryoablation had a significantly shorter hospitalization time than surgery (p = 0.001). Clinically, the post-operative VAS scores were all significantly improved compared to the pre-operative period, and the clinical cure was achieved in both groups. Surgical operations had more complications than cryoablation, although there was no significant difference. In the group of cryoablation, only one patient had mild numbness of the left lower extremity, which relieved itself; two patients had mild post-operative pain. No patients in the cryoablation group experienced recurrence during the follow-up period. In the surgery group, three of the patients experienced massive bleeding (>500 ml), and two underwent transfusion therapy. Only one patient in the surgical resection group experienced a recurrence at 29 months postoperatively and underwent a second resection. All patients had local scars on the skin after surgical resection.

Conclusion

Cryoablation is a minimally invasive, safe, and effective treatment strategy for osteoid osteoma, and is fully comparable to surgical resection.

Focal therapy, time to join the multi-disciplinary team discussion?

Organ preserving management is common place in renal cancer, breast cancer and many other solid organ tumours. Current strategies in managing intermediate risk prostate cancer include either whole gland treatment, in the form of radical radiotherapy or radical prostatectomy, or active surveillance. The former is associated with significant post-treatment functional morbidity, whilst the latter associated with the burden of surveillance activity and patient anxiety. Focal therapy would logically fit as a middle ground for suitable patients in whom treatment would be recommended, but where much better functional outcomes may be possible. Ideally this comes without restricting the successful prevention of harm from the cancer. Historically limitations in developing tissue preserving focal therapy strategies in prostate cancer, were due to inaccuracies in tumour characterisation prior to treatment and during follow up. Consequently for example many patients undergoing an active surveillance strategy were being upgraded and upstaged within a short period. Recently high level evidence supporting the use of MRI and targeted biopsies, in particular the PROMIS and PRECISION trials have strengthened clinician confidence in accurate disease characterisation, thus making focal therapy to become a more feasible management option. With improved diagnostic strategies and the publication of reassuring medium term oncological and functional outcomes after focal therapy for intermediate risk prostate cancer, has the time come to require consideration of focal therapy within our multi-disciplinary team (MDT) meetings and with patients? In this review we will consider patient selection and the evidence for the various focal ablation options as well as the surveillance of these patients after treatment. The forthcoming trials to determine comparative effectiveness will be discussed.

Focal ablation of apical prostate cancer lesions with irreversible electroporation (IRE)

INTRODUCTION AND OBJECTIVE

To assess the safety, oncological and quality-of-life (QoL) outcomes of focal ablation of apical prostate cancer (PCa) lesions with irreversible electroporation (IRE).

METHODS

Patients were included in the study if they had a PCa lesion within 3 mm of the apical capsule treated with IRE. The IRE procedure was performed in our institution by a single urologist. The QoL and functional data was collected prospectively from patients who provided consent using the Expanded Prostate Cancer Index Composite (EPIC). Oncological follow up included 3-month PSA levels, mpMRI at 6 months and transperineal biopsy at 1-year post treatment.

RESULTS

A total of 50 patients had apical PCa lesions treated between February 2013 and September 2018. Median follow-up was 44 months. There were no Clavien-Dindo grade 3 events or higher. No perioperative complications were recorded. No significant difference was observed in the EPIC urinary or bowel QoL domain between baseline and 12-month post-treatment. One patient (2%) required one pad per day for urinary incontinence 12-month post-treatment. There was a small but significant decline in EPIC sexual QoL (65 at baseline and 59 at 12-month post-IRE). Of patient's potent pre-treatment, 94% remained potent after treatment. The median PSA nadir decreased by 71% (6.25-1.7 ng/mL). Only one patient (2.5%) had in-field residual disease on repeat biopsy.

CONCLUSION

Focal ablation using IRE for PCa in the distal apex appears safe and feasible with acceptable early QoL and oncologic outcomes.

Histotripsy: The Next Generation of High-Intensity Focused Ultrasound for Focal Prostate Cancer Therapy

This article reviews the most current methods and technological aspects of high-intensity focused ultrasound (HIFU), which is termed histotripsy. The rationale for focal therapy for prostate carcinoma rather than prostatectomy, which is being used extensively throughout Europe and Asia, is presented, and an argument for why HIFU is the modality of choice for primary therapy and recurrent disease is offered. The article presents a review of the technical advances including higher ultrasound beam energy than current thermal HIFU which allows for more accurate tissue targeting, less collateral tissue damage, and faster treatment times. Finally, the article presents a discussion about the advantage of ultrasound guidance for histotripsy in preference to magnetic resonance imaging guidance primarily based on cost, ease of application, and portability.

Comparison of T2-Weighted Imaging, DWI, and Dynamic Contrast-Enhanced MRI for Calculation of Prostate Cancer Index Lesion Volume: Correlation With Whole-Mount Pathology

OBJECTIVE

The objective of our study was to investigate the comparative effectiveness of different MRI sequences for the estimation of index lesion volume in patients with prostate cancer (PCa) compared with ground truth volume measured on whole-mount pathology.

MATERIALS AND METHODS

Patients with PCa underwent multiparametric MRI (mpMRI) on a 3-T MRI scanner before radical prostatectomy. Forty PCa index lesions were identified and outlined on histology by a pathologist. Two radiologists who were informed about the presence of PCa but were not aware of lesion outlines on histology worked in consensus to delineate PCa lesions on T2-weighted imaging, apparent diffusion coefficient (ADC) maps, and early-phase dynamic contrast-enhanced MRI (DCE-MRI). The lesion volumes from different mpMRI sequences and the percentage of volume underestimation compared with pathology were calculated and correlated with volume at pathology. The repeated-measures ANOVA with the posthoc Bonferroni test was performed to evaluate whether the difference between the estimated tumor volumes was statistically significant.

RESULTS

The mean PCa lesion volume estimated from pathology, T2-weighted imaging, DWI (ADC maps), and DCE-MRI were 4.61 ± 4.99 (SD) cm³, 2.03 ± 2.96 cm³, 1.81 ± 2.76 cm³, and 3.48 ± 4.06 cm³, respectively. The lesion volumes on T2-weighted images (p = 0.000002), ADC maps (p = 0.000003), and DCE-MR images (p = 0.004412) were significantly lower than those from pathology. PCa lesion volume was significantly underestimated on T2-weighted images, ADC maps, and DCE-MR images compared with pathology by 54.98% ± 22.60% (mean ± SD), 58.59% ± 18.58%, and 18.33% ± 30.11%, respectively; underestimation using T2-weighted imaging (p = 1.01 × 10^-11) and DWI (p = 2.94 × 10^-11) was significantly higher than underestimation using DCE-MRI. Correlations between lesion volume estimated on T2-weighted images, ADC maps, and DCE-MR images with pathology were 0.91 (p = 9.03 × 10^-16), 0.86 (p = 7.32 × 10^-13), and 0.93 (p = 8.22 × 10^-18), respectively.

CONCLUSION

DCE-MRI performed better than T2-weighted imaging and DWI for estimation of index PCa volume and therefore can be preferred over these other two sequences for volume estimation.