Evaluation of a novel precision template-guided biopsy system for detecting prostate cancer

Contemporary risk of biochemical recurrence after radical prostatectomy in the active surveillance era

OBJECTIVES

To assess whether contemporary risks of biochemical recurrence (BCR) after radical prostatectomy (RP) in the AS era differ from historical estimates due to changes in tumor risk case mix and improvements in risk stratification.

MATERIALS AND METHODS

We sampled 6,682 men who underwent RP for clinically localized disease between 2000 and 2017 from the VA SEARCH database. Kaplan Meier analysis was used to calculate incidence of BCR before and after 2010 overall and within tumor risk subgroups. Multivariable Cox proportional hazard regression analysis including an interaction term between era and tumor risk was used to compare risk of BCR before and after 2010 overall and across tumor risk subgroups.

RESULTS

About 3,492 (52%) and 3,190 (48%) men underwent RP before and after 2010, respectively. In a limited multivariable model excluding tumor risk, overall BCR risk was higher post-2010 vs. pre-2010 (HR: 1.15, 95%CI: 1.05-1.25; 40% vs 36% at 8 years post-RP). However, this effect was eliminated after correcting for tumor risk (HR: 0.95, 95%CI: 0.87-1.04), suggesting that differences in tumor risk between eras mediated the change. Yet, within tumor-risk subgroups, BCR risk was significantly lower for favorable intermediate-risk (HR: 0.76, 95%CI:0.60-0.96) and unfavorable intermediate-risk PC (HR: 0.78, 95%CI: 0.67-0.90), but significantly higher for high-risk PC (HR: 1.22, 95%CI: 1.07-1.38) in the post-2010 era. 8-year risks of BCR in the post-2010 era were 21% (95%CI: 16%-25%), 25% (95%CI: 20%-30%), 41% (95%CI: 37%-46%), and 60% (95%CI: 56%-64%) for low-, FIR-, UIR-, and high-risk disease, respectively. Limitations include limited long-term follow-up in the post-2010 subgroup.

CONCLUSIONS

Overall BCR risk has increased in the AS era, driven by a higher risk case mix and increased BCR risk among high-risk patients. Physicians should quote contemporary estimates of BCR when counseling patients.

A novel method for pain control: infiltration free local anesthesia technique (INFLATE) for transrectal prostatic biopsy using transcutaneous electrical nerve stimulation (TENS)

PURPOSE

To describe a novel method for the control of pain during prostate biopsies, infiltration free local anesthesia technique (INFLATE) for transrectal prostatic biopsies with no further needle insertions for local anesthetic infiltration.

METHODS

A total of 138 men with elevated prostate-specific antigen levels and/or abnormal digital rectal examination findings were included in the study. Of the patients, 73 were assigned to the INFLATE group and 65 to the TRUS-PNB group. Demographic data, PSA levels, findings of digital rectal examinations, and multiparametric prostatic magnetic resonance imaging were recorded. In the INFLATE group, a two-channel TENStem eco basic device with two electrodes was used for pain control during the biopsy. For the TRUS-PNB group, 60 mg lidocaine gel was given intrarectally in addition to infiltration of a prilocaine and bupivacaine mixture (5 mL of 2% prilocaine + 5 mL of 0.25% bupivacaine). Pain perception was assessed using a linear numeric rating scale.

RESULTS

The mean ages, BMIs, prostate volumes, and PSA levels were similar between the two groups (p > 0.05). Of the 56 participants with prostate adenocarcinoma, 28 were in the INFLATE group, and 28 were in the TRUS-PNB group with a 40.6% overall cancer detection rate. The mean preoperative and post-operative pain scores during probe insertion, biopsy and post-biopsy were similar between the groups (p > 0.05).

CONCLUSION

The results of the study confirmed that INFLATE for transrectal prostate biopsy using a TENS device could safely and effectively be used for pain control with the advantage of two fewer needle attempts with no increase in significant complications.

Robotic ultrasound and needle guidance for prostate cancer management: review of the contemporary literature

PURPOSE OF REVIEW

To present the recent advances in needle guidance and robotic ultrasound technology which are used for prostate cancer (PCa) diagnosis and management.

RECENT FINDINGS

Prostate biopsy technology has remained relatively unchanged. Improved needle localization and precision would allow for better management of this common disease. Robotic ultrasound and needle guidance is one strategy to improve needle localization and diagnostic accuracy of PCa. This review focuses on the recent advances in robotic ultrasound and needle guidance technologies, and their potential impact on PCa diagnosis and management.

SUMMARY

The use of robotic ultrasound and robotic-assisted needle guidance has the potential to improve PCa diagnosis and management.

Optimization of prostate biopsy: review of technique and complications

A 12-core systematic biopsy that incorporates apical and far-lateral cores in the template distribution allows maximal cancer detection and avoidance of a repeat biopsy while minimizing the detection of insignificant prostate cancers. Magnetic resonance imaging-guided prostate biopsy has an evolving role in both initial and repeat prostate biopsy strategies, potentially improving sampling efficiency, increasing the detection of clinically significant cancers, and reducing the detection of insignificant cancers. Hematuria, hematospermia, and rectal bleeding are common complications of prostate needle biopsy, but are generally self-limiting and well tolerated. All men should receive antimicrobial prophylaxis before biopsy.

Considerations for patient selection for focal therapy

Focal therapy for prostate cancer is a nascent and emerging field. As such, the patient selection criteria for this new treatment paradigm are evolving in parallel to both the technology on which this approach depends and to our unfolding understanding of the natural history of prostate cancer. Until, and while, prospective trials of focal therapy are being reported, patient selection criteria will be flexible and very dependent on the therapeutic goals. We must carefully define the therapeutic intentions of focal therapy before engaging in the actual process of determining optimal patient selection. The therapeutic intent will define the most appropriate candidate for such therapy. Patient selection encompasses multiple complex issues including the type of prostate biopsy (12 core transrectal versus mapping transperineal) to the type of imaging (multiparametric magnetic resonance imaging or enhanced ultrasound) to the specific anatomical location of the disease within the prostate (apex, mid-prostate, base) and a comprehensive assessment of the patient's overall health and life expectancy. It is not as simple as saying a patient with a certain grade or a certain number of cores is or is not appropriate for focal therapy. There are many more considerations for a reasonable and thoughtful approach to this new treatment.

Overdiagnosis of prostate cancer

This chapter addresses issues relevant to prostate cancer overdiagnosis. Factors promoting the overdiagnosis of prostate cancer are reviewed. First is the existence of a relatively large, silent reservoir of this disease, as can be seen by evaluating autopsy studies and histologic step-sectioning results of prostates removed for other causes. The second main factor responsible for prostate cancer overdiagnosis is fairly widespread prostate-specific antigen and digital rectal examination-based screening, which has been fairly widely practiced in the United States for the past 20 years among heterogeneous groups of men. This has resulted in the identification of many men from this reservoir who otherwise may never have been diagnosed with symptomatic prostate cancer and is substantially responsible for the current annual incidence to mortality ratio for prostate cancer of approximately 6 to 1. Finally, the relatively indolent natural history and limited cancer-specific mortality as reported in a variety of contemporary randomized screening and treatment trials is reviewed. We attempt to quantitate the proportion of newly diagnosed prostate cancers that are overdiagnosed using various trial results and models. We explore the impact of prostate cancer overdiagnosis in terms of patient anxiety and the potential for overtreatment, with its attendant morbidity. We explore strategies to minimize overdiagnosis by targeting screening and biopsy only to men at high risk for aggressive prostate cancer and by considering the use of agents such as 5-alpha reductase inhibitors. Future prospects to prevent overtreatment, including better biopsy and molecular characterization of newly diagnosed cancer and the role of active surveillance, are discussed.

A biomedical engineering approach to mitigate the errors of prostate biopsy

The current protocol for detecting and ruling out prostate cancer involves serum PSA testing followed by sampling of the prostate using a transrectal ultrasonography (TRUS)-guided biopsy. Many specialists have discussed how PSA screening has contributed to underdetection of clinically significant prostate cancer, overdiagnosis of clinically insignificant disease and poor risk stratification; however, little consideration has been given to the role of TRUS-guided biopsy in these errors. The performance of TRUS-guided biopsy is constrained by the biomechanical attributes of the sampling strategy, resulting in suboptimal detection efficiency of each core. By using a biomedical engineering approach, a uniform grid sampling strategy could be used to improve the detection efficiency of prostate biopsy. Moreover, the calibration of the sampling can be adjusted by altering the distance between needle deployments. Our model shows that for any given number of needle trajectories, a uniform grid approach will be superior to a divergent, nonuniform strategy for the detection of clinically important disease. This is an important message that should result in a move away from divergent sampling to a uniform grid approach for prostate biopsy.

Focal therapy for prostate cancer: patient selection and evaluation

Recent stage migration toward low-risk prostate cancer, overtreatment of biologically insignificant tumors with radical prostatectomy at the additional expense of a non-negligible morbidity and undertreatment of patients improperly selected for active surveillance are the main reasons that have fueled the concept of focal therapy. Optimal selection of patients is the key for the successful implementation of focal therapy. Selection criteria for focal therapy vary widely and depend on clinical, histological and imaging characteristics of the patients that are highlighted in this article. In addition, the rationales, merits and limitations of the available methods for the assessment of potential candidates, the evaluation of treatment efficacy and follow-up of these patients are discussed.

Robotic transperineal prostate biopsy: pilot clinical study

OBJECTIVE

To develope a robot (BioXbot) that performs mapping transperineal prostate biopsy (PB) with two perineal skin punctures under ultrasound guidance. Our pilot study's clinical endpoints were complications and its technical endpoints were the duration for each phase.

METHODS

This institution review board-approved prospective clinical trial included patients with indications for PB. Two urologists performed these PBs. In the lithotomy position and under general anesthesia, the transrectal biplane ultrasound probe acquired transverse images of the prostate gland. The urologist defined its boundaries and planned the biopsy. It guided the PB in 3 axes, passing through a single perineal skin puncture for each prostate side. After each biopsy, it automatically moved to the next position. The steps were repeated on the contralateral side.

RESULTS

Our 20 patients had a mean prostate-specific antigen of 8.4 ± 4.9 ng/mL. Two patients had 2 previous biopsies, whereas the rest had one. The mean number of biopsies taken was 28.5 ± 6.2 in a mean total procedure time of 32.5 ± 3.2 minutes. We detected 3 patients with prostate cancer with Gleason score 3 + 3. Two patients required brief bladder catheterization after their biopsy. Their prostate volumes were >50 mL and the number of biopsies taken was >30 cores. There was no mechanical failure, sepsis, bleeding per-rectal, or perineal hematoma.

CONCLUSION

This pilot study demonstrated BioXbot's safety and feasibility as a biopsy platform. It can potentially be used for image-guided PB and focal therapy.

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.

Primary care perspectives on prostate cancer screening

Although the effectiveness of prostate cancer screening is controversial, screening rates have risen dramatically among primary care providers in the United States. The authors' findings suggest more collaboration among primary care and specialty organizations, especially with respect to decision aid endorsement, is needed to achieve more discriminatory and patient-centered prostate cancer screening.

Limitations of a contemporary prostate biopsy: the blind march forward

In an attempt to reduce morbidity, focal targeted therapies and active surveillance have become increasingly popular treatment choices for localized prostate cancer. However, these modalities rely heavily on accurate and reliable tumor localization information provided by a prostate biopsy. Evidence that our contemporary biopsy techniques can do little more than detect some prostate cancers is notably lacking. What is meant by the accuracy and reliability of a prostate biopsy and why they are such important concepts to focal therapy and active surveillance are discussed.

Prostate biopsy in selecting candidates for hemiablative focal therapy

Focal therapy (FT) for the management of clinically localized prostate cancer (PCa) is growing from a concept to reality because of increased interest of both patients and physicians. Selection protocols, however, are yet to be established. We discuss the role of prostate biopsy in candidate selection for FT and highlight the different strategies and technical aspects of the use of prostate biopsy in this setting. In our opinion, prostate biopsy plays a major role in the selection process and tailoring appropriate treatment strategy to the patient. FT necessitates dedicated biopsy schemes that would reliably predict the extent, nature, and location of PCa in selected patients. Currently, there is insufficient scientific evidence to propose a specific biopsy scheme that could fit every candidate, providing accurate characterization of the disease in the individual patient. Further research is necessary to establish solid selection protocols that would reliably identify appropriate candidates for FT of PCa.

Candidate selection for prostate cancer focal therapy

Focal therapy has emerged as a potential treatment paradigm for men with localized prostate cancer, because it serves as a medium between the ambiguity of surveillance and the potential reduction of quality of life observed with radical treatment. Candidate selection remains the major challenge of implementing focal therapy in clinical practice. While focal therapy is potentially widely applicable, there is general consensus that initial efforts to initiate focal therapy protocols in practice should be limited to men with disease features that are low to low-intermediate risk, thereby limiting the likelihood of early systemic failure. Selection of candidates is first dependent on the intent of focal therapy. Curative intent focal therapy is limited to a small number of men with isolated, low-risk, unifocal, or unilateral disease. In men for whom local control-and potential prolongation of the natural history of disease-is desired, mapping strategies would focus on identification of the dominant site of disease and ruling out high-risk features. Tools such as conventional transrectal biopsy, transperineal saturation biopsy, and prostate MRI all have relative merits and shortcomings. While ultimately limitation of biopsy is desirable through combinations of transrectal biopsy and imaging, for now, limitations of conventional imaging modalities make it likely that most men will need transperineal saturation biopsy before inclusion in focal therapy protocols.

Temporal-based needle segmentation algorithm for transrectal ultrasound prostate biopsy procedures

PURPOSE

Automatic identification of the biopsy-core tissue location during a prostate biopsy procedure would provide verification that targets were adequately sampled and would allow for appropriate intraprocedure biopsy target modification. Localization of the biopsy core requires accurate segmentation of the biopsy needle and needle tip from transrectal ultrasound (TRUS) biopsy images. A temporal-based TRUS needle segmentation algorithm was developed specifically for the prostate biopsy procedure to automatically identify the TRUS image containing the biopsy needle from a collection of 2D TRUS images and to segment the biopsy-core location from the 2D TRUS image.

METHODS

The temporal-based segmentation algorithm performs a temporal analysis on a series of biopsy TRUS images collected throughout needle insertion and withdrawal. Following the identification of points of needle insertion and retraction, the needle axis is segmented using a Hough transform-based algorithm, which is followed by a temporospectral TRUS analysis to identify the biopsy-needle tip. Validation of the temporal-based algorithm is performed on 108 TRUS biopsy sequences collected from the procedures of ten patients. The success of the temporal search to identify the proper images was manually assessed, while the accuracies of the needle-axis and needle-tip segmentations were quantitatively compared to implementations of two other needle segmentation algorithms within the literature.

RESULTS

The needle segmentation algorithm demonstrated a >99% accuracy in identifying the TRUS image at the moment of needle insertion from the collection of real-time TRUS images throughout the insertion and withdrawal of the biopsy needle. The segmented biopsy-needle axes were accurate to within 2.3 +/- 2.0 degrees and 0.48 +/- 0.42 mm of the gold standard. Identification of the needle tip to within half of the biopsy-core length (<10 mm) was 95% successful with a mean error of 2.4 +/- 4.0 mm. Needle-tip detection using the temporal-based algorithm was significantly more accurate (p < 0.001) than the other two algorithms tested, while the segmentation of the needle axis was not significantly different between the three algorithms.

CONCLUSIONS

The temporal-based needle segmentation algorithm accurately segments the location of the biopsy core from 2D TRUS images of clinical prostate biopsy procedures. The results for needle-tip localization demonstrated that the temporal-based algorithm is significantly more accurate than implementations of some existing needle segmentation algorithms within the literature.

Biopsy accuracy in identifying unilateral prostate cancer depends on prostate weight

OBJECTIVE

To evaluate the association between prostate weight and the diagnostic performance of routine biopsy schemes in detecting unilateral prostate cancer (PCa) that may be amenable to focal therapy.

METHODS AND MATERIALS

Retrospective analysis of patients undergoing radical prostatectomy at Duke University Medical Center from 1990 to 2007. The cohort was dichotomized according to prostate weight (≤40 and >40 g) and further divided by biopsy scheme: 6-9 (sextant) and 10-20 cores (extended). Diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were calculated within each prostate weight group and compared between biopsy schemes.

RESULTS

A total of 859 patients were included in the study. Patients with prostates >40 g were generally older and had higher PSA levels (P < 0.0001 and P = 0.036, respectively). Unilateral disease was more common in prostates >40 g both on biopsy (69% vs. 60%, P = 0.009) and on final pathology (21% vs. 14%, P = 0.017) despite larger total tumor volume (6.1 vs. 4.8 cc, P < 0.001). Low grade PCa was also more common in larger glands (P = 0.003). Overall, extended biopsy schemes performed better than sextant but the benefit was statistically significant only in prostates >40 g.

CONCLUSIONS

Despite having higher tumor volumes, men with prostate weight >40 g were more likely to have unilateral PCa than those with smaller prostates. In prostates >40 g, increasing the number of cores harvested at biopsy increased the diagnostic performance for detecting cancer laterality. Therefore, our results suggest that the benefit of more extensive tissue sampling may be higher in larger prostates compared with smaller ones when selecting candidates for prostate hemiablation.

Prostate cancer: the new landscape

PURPOSE OF REVIEW

This review highlights current features of the changing landscape of the US population with newly diagnosed prostate cancer and discusses new treatment options utilizing noninvasive or minimally invasive management.

RECENT FINDINGS

Recent evidence of significant changes in the current prostate cancer landscape is based on clinical data and pathological specimens after radical prostatectomy that suggest a further increase of the low-risk patient population that may require reconsideration of treatment options. For a select cohort of patients with low-risk features, based on the D'Amico definition, active surveillance or focal ablative therapy may be a rational alternative to surgical prostatectomy or whole-gland radiation therapy that still dominate as the main treatment approaches for localized prostate cancer.

SUMMARY

As the prostate-specific antigen era continues to mature, we continue to witness stage migration. A growing segment of the localized prostate cancer patient population has very low-volume, low-grade disease. Although active surveillance may be an appropriate approach for a selected group of patients, the progression requiring whole-gland therapy remains a challenge. Organ-sparing focal therapy might ideally fill the gap between a surveillance strategy and whole-gland treatment providing a reasonable balance between cancer control and quality of life.

Utility of a 3-Dimensional Transrectal Ultrasound-guided Prostate Biopsy System for Prostate Cancer Detection

The 3-D transrectal ultrasound (TRUS)-guided prostate biopsy system is a novel device that allows precise needle placement in a template fashion. We evaluate its utility for prostate cancer (PCa) detection. A retrospective analysis was performed evaluating 68 prospective patients at the Duke Prostate Center who underwent a prostate biopsy using a 3-D TRUS-guided system. After creation of a three-dimensional map of the prostate, a computer algorithm identified an ideal biopsy scheme based on the measured dimensions of the prostate. The system then used a fixed template that allowed prostate biopsy at specific locations with the ability to target the same region of the prostate in the future if needed. For all patients, a 12-core biopsy pattern was used to cover medial and lateral areas of the base, mid-gland, and apex. In total, 68 patients underwent 3-D TRUS-guided prostate biopsies between April 2006 and November 2007 for prostate cancer detection. The indication for prostate biopsy was PSA ≥ 4.0 ng/ml in 47 (69%) patients, abnormal digital rectal examination (DRE) in 17 (25%), and atypia on previous biopsy in 4 (6%) patients. Prostate cancer was detected in 18 patients (26.5%) and 7 (10.3%) had atypical small acinar proliferation (ASAP). The highest frequency (55.5%) from all cases of cancer detected was identified when 3-D TRUS biopsy was used as the initial biopsy. This study demonstrates that a 3-D TRUS-guided biopsy system translates to a more frequent detection of prostate cancer among patients undergoing an initial prostate biopsy than a subsequent one. More comprehensive studies are warranted to corroborate and extend the results of this study.

Mechanically assisted 3D ultrasound guided prostate biopsy system

There are currently limitations associated with the prostate biopsy procedure, which is the most commonly used method for a definitive diagnosis of prostate cancer. With the use of two-dimensional (2D) transrectal ultrasound (TRUS) for needle-guidance in this procedure, the physician has restricted anatomical reference points for guiding the needle to target sites. Further, any motion of the physician's hand during the procedure may cause the prostate to move or deform to a prohibitive extent. These variations make it difficult to establish a consistent reference frame for guiding a needle. We have developed a 3D navigation system for prostate biopsy, which addresses these shortcomings. This system is composed of a 3D US imaging subsystem and a passive mechanical arm to minimize prostate motion. To validate our prototype, a series of experiments were performed on prostate phantoms. The 3D scan of the string phantom produced minimal geometric distortions, and the geometric error of the 3D imaging subsystem was 0.37 mm. The accuracy of 3D prostate segmentation was determined by comparing the known volume in a certified phantom to a reconstructed volume generated by our system and was shown to estimate the volume with less then 5% error. Biopsy needle guidance accuracy tests in agar prostate phantoms showed that the mean error was 2.1 mm and the 3D location of the biopsy core was recorded with a mean error of 1.8 mm. In this paper, we describe the mechanical design and validation of the prototype system using an in vitro prostate phantom. Preliminary results from an ongoing clinical trial show that prostate motion is small with an in-plane displacement of less than 1 mm during the biopsy procedure.

Prostate cancer: diagnosis and staging

Prostate cancer represents an increasing health burden. The past 20 years, with the introduction of prostate-specific antigen (PSA), has seen prostate cancer move increasingly from a condition that presented with locally advanced disease or metastases to one that is found upon screening. More is also known about the pathology of pre-malignant lesions. Diagnosis relies on trans-rectal ultrasound (TRUS) to obtain biopsies from throughout the prostate, but TRUS is not useful for staging. Imaging for staging, such as magnetic resonance imaging or computed tomography, still has a low accuracy compared with pathological specimens. Current techniques are also inaccurate in identifying lymph node and bony metastases. Nomograms have been developed from the PSA, Gleason score and clinical grading to help quantify the risk of extra-capsular extension in radical prostatectomy specimens. Improved clinical staging modalities are required for more reliable prediction of pathological stage and for monitoring of response to treatments.