Evaluation of Color Doppler in Guiding Prostate Biopsy after HIFU Ablation

Non-Invasive Diagnosis of Prostate Cancer and High-Grade Prostate Cancer Using Multiparametric Ultrasonography and Serological Examination

OBJECTIVES

This study aimed to assess the efficacy of multiparametric ultrasonography (mpUS) combined with serological examination, as a non-invasive method, in detecting prostate cancer (PCa) or high-grade prostate cancer (HGPCa) respectively.

METHODS

A cohort of 245 individuals with clinically suspected PCa were enrolled. All subjects underwent a comprehensive evaluation, including basic data collection, serological testing, mpUS and prostate biopsy. Random Forest (RF) models were developed, and the mean area under the curve (AUC) in 100 cross-validations was used to assess the performance in distinguishing PCa from HGPCa.

RESULTS

mpUS features showed significant differences (p < 0.001) between the PCa and non-PCa groups, as well as between the HGPCa and low-grade prostate cancer (LGPCa) groups including prostate-specific antigen density (PSAD), transrectal real-time elastography (TRTE) and intensity difference (ID). The RF model, based on these features, demonstrated an excellent discriminative ability for PCa with a mean area under the curve (AUC) of 0.896. Additionally, another model incorporating free prostate-specific antigen (FPSA) and color Doppler flow imaging (CDFI) achieved a high accuracy in predicting HGPCa with a mean AUC of 0.830. The nomogram derived from these models exhibited excellent individualized prediction of PCa and HGPCa.

CONCLUSION

The RF models incorporating mpUS and serological variables achieved satisfactory accuracies in predicting PCa and HGPCa.

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

Since there are salvage solutions, it is important to detect local recurrence of prostate cancer as early as possible. The first sign is "biochemical failure" in that the prostate specific antigen (PSA) concentration rises again. The definition of biochemical failure varies depending on the initial treatment: PSA greater than 0.2ng/mL after prostatectomy, nadir+2ng/mL after radiotherapy. There is no standardised definition of biochemical failure after cryotherapy, focused ultrasound, or brachytherapy. Magnetic resonance imaging (MRI) (particularly dynamic MRI) can detect local recurrence with good sensitivity. The role of spectroscopy is still under discussion. For the moment, ultrasound techniques are less effective than MRI.

Lithium niobate transducers for MRI-guided ultrasonic microsurgery

Focused ultrasound surgery (FUS) is usually based on frequencies below 5 MHz-typically around 1 MHz. Although this allows good penetration into tissue, it limits the minimum lesion dimensions that can be achieved. In this study, we investigate devices to allow FUS at much higher frequencies, in principle, reducing the minimum lesion dimensions. Furthermore, FUS can produce deep-sub-millimeter demarcation between viable and necrosed tissue; high-frequency devices may allow this to be exploited in superficial applications which may include dermatology, ophthalmology, treatment of the vascular system, and treatment of early dysplasia in epithelial tissue. In this paper, we explain the methodology we have used to build high-frequency high-intensity transducers using Y-36°-cut lithium niobate. This material was chosen because its low losses give it the potential to allow very-high-frequency operation at harmonics of the fundamental operating frequency. A range of single-element transducers with center frequencies between 6.6 and 20.0 MHz were built and the transducers' efficiency and acoustic power output were measured. A focused 6.6-MHz transducer was built with multiple elements operating together and tested using an ultrasound phantom and MRI scans. It was shown to increase phantom temperature by 32°C in a localized area of 2.5 x 3.4 mm in the plane of the MRI scan. Ex vivo tests on poultry tissue were also performed and shown to create lesions of similar dimensions. This study, therefore, demonstrates that it is feasible to produce high-frequency transducers capable of high-resolution FUS using lithium niobate.

Location of residual cancer after transrectal high-intensity focused ultrasound ablation for clinically localized prostate cancer

What's known on the subject ? and What does the study add? Transrectal High-Intensity Focused Ultrasound (HIFU) ablation has been used as a minimally invasive treatment for localized prostate cancer for 15 years. Five-year disease-free survival rates of 66-78% have been reported, challenging the results of external-beam radiation therapy. Usually, a 6-mm safety margin is used in the apex to preserve the urinary sphincter and potency. The influence of this 6-mm margin on the results of the treatment has never been assessed. This retrospective study of a cohort of 99 patients who underwent systematic biopsy 3-6 months after HIFU ablation for prostate cancer (with a 6-mm safety margin in the apex) shows that post-HIFU residual cancer is found more frequently in the apex. Therefore, new strategies improving the prostate destruction at the apex while preserving the urinary continence need to be found.

OBJECTIVE

• To evaluate whether the location (apex/midgland/base) of prostate cancer influences the risk of incomplete transrectal high-intensity focused ultrasonography (HIFU) ablation.

PATIENTS AND METHODS

• We retrospectively studied 99 patients who underwent prostate cancer HIFU ablation (Ablatherm; EDAP, Vaulx-en-Velin, France) with a 6-mm safety margin at the apex, and had systematic biopsies 3-6 months after treatment. • Locations of positive pre- and post-HIFU sextants were compared. • The present study included two analyses. First, sextants negative before and positive after treatment were recoded as positive/positive, hypothesizing that cancer had been missed at pretreatment biopsy. Second, patients with such sextants were excluded.

RESULTS

• Pre-HIFU biopsies found cancer in all patients and in 215/594 sextants (36.2%); 55 (25.6%) positive sextants were in the apex, 86 (40%) in the midgland and 74 (34.4%) in the base. • After treatment, residual cancer was found in 36 patients (36.4%) and 50 sextants (8.4%); 30 (60%) positive sextants were in the apex, 12 (24%) in the midgland and eight (16%) in the base. • Both statistical analyses found that the locations of the positive sextants before and after HIFU ablation were significantly different (P < 0.001), with a higher proportion of positive apical sextants after treatment. • At the first analysis, the mean (95% confidence interval) probability for a sextant to remain positive after HIFU ablation was 8.8% (3.5-20.3%) in the base, 12.7% (5.8-25.9%) in the midgland and 41.7% (27.2-57.89%) in the apex. • At the second analysis, these same probabilities were 5.9% (1.9-17%), 9.9% (3.9-23.2%) and 27.3% (13.7-47%), respectively.

CONCLUSION

• When a 6-mm apical safety margin is used, residual cancer after HIFU ablation is found significantly more frequently in the apex.

Role of imaging and biopsy to assess local recurrence after definitive treatment for prostate carcinoma (surgery, radiotherapy, cryotherapy, HIFU)

PURPOSE

Defining the site of recurrent disease early after definitive treatment for a localized prostate cancer is a critical issue as it may greatly influence the subsequent therapeutic strategy or patient management.

METHODS

A systematic review of the literature was performed by searching Medline from January 1995 up to January 2011. Electronic searches were limited to the English language, and the keywords prostate cancer, radiotherapy [RT], high intensity focused ultrasound [HIFU], cryotherapy [CRIO], transrectal ultrasound [TRUS], magnetic resonance [MRI], PET/TC, and prostate biopsy were used.

RESULTS

Despite the fact that diagnosis of a local recurrence is based on PSA values and kinetics, imaging by means of different techniques may be a prerequisite for effective disease management. Unfortunately, prostate cancer local recurrences are very difficult to detect by TRUS and conventional imaging that have shown limited accuracy at least at early stages. On the contrary, functional and molecular imaging such as dynamic contrast-enhanced MRI (DCE-MRI), and diffusion-weighted imaging (DWI), offers the possibility of imaging molecular or cellular processes of individual tumors. Recently, PET/CT, using 11C-choline, 18F-fluorocholine or 11C-acetate has been successfully proposed in detecting local recurrences as well as distant metastases. Nevertheless, in controversial cases, it is necessary to perform a biopsy of the prostatic fossa or a biopsy of the prostate to assess the presence of a local recurrence under guidance of MRI or TRUS findings.

CONCLUSION

It is likely that imaging will be extensively used in the future to detect and localize prostate cancer local recurrences before salvage treatment.

Diffusion weighted imaging in prostate cancer

Diffusion-weighted imaging has generated substantial interest in the hope that it can be developed into a robust technique to improve the accuracy of MRI for the evaluation of prostate cancer. This technique has the advantages of short acquisition times, no need for intravenous administration of contrast medium, and the ability to study diffusion of water molecules that indirectly reflects tissue cellularity. In this article, we review the existing literature on the utility of DWI in tumour detection, localisation, treatment response, limitations of the technique, how it compares with other imaging techniques, technical considerations and future directions.

High-intensity focused ultrasound: where are we and where to from here?

High-intensity focused ultrasound (HIFU) has evolved significantly from early work treating cerebral lesions. The ability to treat deep soft-tissue lesions without damaging superficial structures led to it being used for prostate cancer treatment both in the primary and salvage setting. Primary HIFU treatment for prostate cancer leads to 5-year disease free survival rates of up to 70-80% in selected patients with little morbidity; however, comparative studies with established treatment modalities are lacking. Salvage treatment with HIFU leads to significantly more morbidity than primary treatment yet the morbidity appears the same or less than other salvage treatments following external-beam radiation treatment. We believe that with the development of more advanced imaging techniques combined with multimodality prostate imaging that HIFU's future lies in focal treatment of prostate cancer.

Rapid photothermal intracellular drug delivery using multiwalled carbon nanotubes

Carbon nanotubes are unique materials that absorb infrared (IR) radiation, especially between 700 and 1100 nm, where body tissues are most transparent. Absorbed IR promotes molecular oscillation leading to efficient heating of the surrounding environment. A method to enhance drug localization for peritoneal malignancies is perfusion of warm (40-42 degrees C) chemotherapeutic agents in the abdomen. However, all tissues in the peritoneal cavity are subjected to enhanced drug delivery due to increased cell membrane permeability at hyperthermic temperatures. Here we show that rapid heating (within ten seconds) of colorectal cancer cells to 42 degrees C, using infrared stimulation of nanotubes as a heat source, in the presence of the drugs oxaliplatin or mitomycin C, is as effective as two hours of radiative heating at 42 degrees C for the treatment of peritoneal dissemination of colorectal cancer. We demonstrate increased cell membrane permeability due to hyperthermia from multiwalled carbon nanotubes in close proximity to cell membranes and that the amount of drug internalized by colorectal cancer cells heated quickly using carbon nanotubes equals levels achieved during routine application of hyperthermia at 42 degrees C. This approach has the potential to be used as a rapid bench to bedside clinical therapeutic agent with significant impact for localizing chemotherapy agents during the surgical management of peritoneal dissemination of colorectal cancer.

Prostate cancer transrectal HIFU ablation: detection of local recurrences using T2-weighted and dynamic contrast-enhanced MRI

The objective was to evaluate T2-weighted (T2w) and dynamic contrast-enhanced (DCE) MRI in detecting local cancer recurrences after prostate high-intensity focused ultrasound (HIFU) ablation. Fifty-nine patients with biochemical recurrence after prostate HIFU ablation underwent T2-weighted and DCE MRI before transrectal biopsy. For each patient, biopsies were performed by two operators: operator 1 (blinded to MR results) performed random and colour Doppler-guided biopsies ("routine biopsies"); operator 2 obtained up to three cores per suspicious lesion on MRI ("targeted biopsies"). Seventy-seven suspicious lesions were detected on DCE images (n = 52), T2w images (n = 2) or both (n = 23). Forty patients and 41 MR lesions were positive at biopsy. Of the 36 remaining MR lesions, 20 contained viable benign glands. Targeted biopsy detected more cancers than routine biopsy (36 versus 27 patients, p = 0.0523). The mean percentages of positive cores per patient and of tumour invasion of the cores were significantly higher for targeted biopsies (p < 0.0001). The odds ratios of the probability of finding viable cancer and viable prostate tissue (benign or malignant) at targeted versus routine biopsy were respectively 3.35 (95% CI 3.05-3.64) and 1.38 (95% CI 1.13-1.63). MRI combining T2-weighted and DCE images is a promising method for guiding post-HIFU biopsy towards areas containing recurrent cancer and viable prostate tissue.

Contrast-enhanced ultrasound and prostate cancer; a multicentre European research coordination project

CONTEXT

Contrast-enhanced ultrasound is a real-time imaging technique with the capability of visualizing perfusion patterns. Since tumour growth is associated with changes in vascularisation, this modality is under research for imaging of various tumour types. Studies have shown promising results for the diagnosis of prostate cancer for various imaging techniques; however, the exact value of each technique is still unclear.

OBJECTIVE

To determine the value of contrast-enhanced ultrasound (CEUS) in the detection, localisation, and follow-up of treatment for prostate cancer.

EVIDENCE ACQUISITION

In the period 2002-2006, research in four European centres regarding CEUS of the prostate was coordinated in a combined program. This paper describes and combines the results of these studies.

EVIDENCE SYNTHESIS

Various techniques were developed and researched during the period of this program. Studies showed that prostate cancer could be visualized and localized in up to 78%. Visualization of the tumour enabled better detection; targeted biopsies lead to fewer biopsies per session without loss of detection rate. A combined approach offered the highest detection rate. CEUS could be used to visualize the effects of high-intensity focussed ultrasound and hormonal therapy for prostate cancer with success, and identified patients with an early relapse. Unfortunately, pretreatment evaluation could not identify the nonresponders beforehand.

CONCLUSIONS

This research project was a first step towards routine use of CEUS in the clinical detection and follow-up of prostate cancer; and new combined studies are initiated.

PSA Nadir Is a Significant Predictor of Treatment Failure after High-Intensity Focussed Ultrasound (HIFU) Treatment of Localised Prostate Cancer

OBJECTIVES

To assess if prostate-specific antigen (PSA) nadir is an independent predictor of treatment failure and disease-free survival after high-intensity focussed ultrasound (HIFU) therapy for localised prostate cancer as defined by the new ASTRO criteria.

METHODS

One hundred three patients after HIFU treatment (Ablatherm, EDAP, Lyon, France) for localised prostate cancer without previous hormonal therapy were evaluated retrospectively. Patients attended regular follow-up visits every 3 mo. Treatment failure was defined by the revised ASTRO criteria (PSA >or=2 ng/ml above nadir PSA, positive biopsy, if salvage treatment was administered). Patients were divided into three PSA nadir subgroups (group 1, <or=0.2 ng/ml; group 2, 0.21-1 ng/ml; group 3, >1 ng/ml). The disease-free survival rate (DFSR) was calculated by using life table methods. The log-rank test was used to compare the curves based on Kaplan-Meier models.

RESULTS

The median follow-up was 4.9 (3-8.6) yr. Mean time to PSA nadir was 6.4+/-5.1 mo. A PSA nadir of <or=0.2 ng/ml, 0.21-1 ng/ml, and >1ng/ml was reached by 64%, 22.3%, and 13.6% of patients, respectively. Treatment failure rates during follow-up were 4.5%, 30.4%, and 100%, respectively, for the three groups (p<0.001). The actuarial DFSRs at 5 yr were 95%, 55%, and 0%, respectively, for the 3 groups (p<0.001).

CONCLUSIONS

The PSA nadir after HIFU correlates highly significantly with treatment failure and DFSR, and can be applied in daily clinical practice. Promising oncological outcome is obtained if a PSA nadir of <or=0.2 ng/ml is reached.

High-intensity focused ultrasound: current potential and oncologic applications

OBJECTIVE

The objective of this article is to introduce the reader to the principles and applications of high-intensity focused ultrasound (HIFU).

CONCLUSION

Although a great deal about HIFU physics is understood, its clinical applications are currently limited, and multiple trials are underway worldwide to determine its efficacy.

First analysis of the long-term results with transrectal HIFU in patients with localised prostate cancer

OBJECTIVE

To evaluate the long-term efficacy of high-intensity focused ultrasound (HIFU) therapy for patients with localised prostate cancer.

MATERIAL AND METHODS

Patients included in this multicentre analysis had T1-T2 NxM0 prostate cancer, a PSA<15 ng/ml, and a Gleason score (GS) < or = 7, and were treated with prototypes or first-generation Ablatherm HIFU devices between October 1997 and August 2001. The Phoenix definition of biochemical failure was used (PSA nadir+2). Treatment failure was defined as: biochemical failure or positive biopsy.

RESULTS

A total of 140 patients with a mean (SD) age 69.1 yr (6.6) were included. Mean (SD) follow-up was 6.4 yr (1.1). Control prostate biopsies were negative in 86.4% of patients. Median PSA nadir of 0.16 ng/ml (range, 0.0-9.1) was achieved at a mean (SD) of 4.9 mo (5.2). A PSA nadir < or = 0.5 ng/ml was recorded in 68.4% of patients. The actuarial biochemical failure-free survival rates (SR) at 5 and 7 yr were 77% and 69%, respectively. The actuarial disease-free SR at 5 and 7 yr were 66% and 59%, respectively.

CONCLUSIONS

This study demonstrates the effective long-term cancer control achieved with HIFU in patients with low- or intermediate-risk localised prostate cancer.

Transrectal high-intensity focused ultrasound ablation of prostate cancer: Effective treatment requiring accurate imaging

Transrectal HIFU ablation has become a reasonable option for the treatment of localized prostate cancer in non-surgical patients, with 5-year disease-free survival similar to that of radiation therapy. It is also a promising salvage therapy of local recurrence after radiation therapy. These favourable results are partly due to recent improvements in prostate cancer imaging. However, further improvements are needed in patient selection, pre-operative localization of the tumor foci, assessment of the volume treated and early detection of recurrence. A better knowledge of the factors influencing the HIFU-induced tissue destruction and a better pre-operative assessment of them by imaging techniques should improve treatment outcome. Whereas prostate HIFU ablation is currently performed under transrectal ultrasound guidance, MR guidance with real-time operative monitoring of temperature will be available in the near future. If this technique will give better targeting and more uniform tissue destruction, its cost-effectiveness will have to be carefully evaluated. Finally, a recently reported synergistic effect between HIFU ablation and chemotherapy opens possibilities for treatment in high-risk or clinically advanced tumors.