Patients and Methods
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The current study was a retrospective analysis of an institutional research and ethics board approved, prospectively accrued database of patients who were consecutively referred by their general practitioner for investigation of an abnormal digital rectal examination or a raised age-specific PSA value, undergoing first-time outpatient prostatic biopsies at West Suffolk Hospital, Bury St Edmunds, UK between June 2009 and June 2011. All patients undergoing repeat prostatic biopsies were excluded from the analysis. The primary endpoint of this study was to compare prostate cancer detection rates between a physician and an NPP. The secondary endpoint of this study was to investigate whether the choice of TRUSP operator was predictive of a positive prostatic biopsy and whether a learning curve existed for this procedure.
Once a referral was received by the Cancer Referrals Office, patients were sequentially allocated to be seen in either an NPP (nurse) -led TRUSP clinic or a physician (urologist) -led clinic. All patients booked in the NPP-led TRUSP clinic were given the choice of a physician operator if preferred. The NPP (KT) had just finished her intensive, structured training on performing TRUSP so this series represents her initial experience with the procedure. In contrast, the urologist in the same institution (JM) had over 20 years of experience in performing the procedure.
The structured TRUSP training programme comprised the NPP obtaining a detailed knowledge of the prostatic anatomy, operation of the transrectal ultrasound scan machine as well as learning the methodology for prostatic biopsy sampling from an expert consultant urologist mentor (JM) at the same institution. A regular, formal summative assessment of competence was performed by an external consultant urologist assessor (PD). The novice NPP was allowed to commence performing TRUSP biopsies independently only when both her local mentor and the external assessor were satisfied with her performance and competence in the procedure, but always with an experienced urologist available close by.
All TRUSP were undertaken in an outpatient setting using a BK Medical (White Waltham, Berkshire, UK) ultrasound scanner equipped with a 5–10 MHz transrectal probe. Informed consent was obtained from all patients before administration of prophylactic antibiotics (ciprofloxacin 500 mg given orally 1 h before the procedure and continued twice daily for a total of 3 days). Patients were positioned in the left lateral decubitus position and received 10 mL 0.5% bupivicaine local anaesthetic injected rectally into the periprostatic nerve plexus. A standardized, template-based series of 10–12 prostate biopsies directed towards the mid-lobe peripheral zone and the lateral peripheral zone of the prostate was taken using an 18 G × 20-cm biopsy needle from Bard Magnum biopsy instrument system (Bard Ltd, Crawley, UK) loaded onto a biopsy gun. Patient variables such as age, presenting PSA levels, prostatic volume, digital rectal examination and biopsy outcome were recorded prospectively on a secure database.
All statistical analyses were performed using SPSS® Version 20 (SPSS Inc., Chicago, IL, USA). A total study sample of 366 patients undergoing prostatic biopsies with a positive biopsy rate of 50% in the physician-led TRUSP service was needed to detect a 15% difference in prostate cancer detection rates in the NPP-led TRUSP service. With this sample size, the study power (1 – β) at an α error rate of 5% was 80%. Continuous data variables were analysed using Mann–Whitney U test and categorical variables were analysed using Pearson's chi-squared test. A multivariate binary logistic regression model was fitted for the prediction of positive prostatic biopsy outcome with age, presenting PSA level, prostatic volume, clinical stage and TRUSP operator all entering the model as explanatory variables. Predictive accuracy was quantified as the area under the receiver operating characteristic curve (AUC), where a value of 100% depicted perfect prediction and 50% was equivalent to a 50/50% chance. A two-sided P value of <0.05 was considered to be statistically significant.
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In total, 440 patients were included in this study with 220 patients in each of the NPP-led and physician-led TRUSP groups. The baseline characteristics of the study cohort are shown in Table 1.
Table 1. Baseline characteristics of the study cohort
| ||Physician (n = 220)||Nurse (n = 220)||P|
|Median age, years (IQR)||67 (61–73)||69 (63–75)||0.08*|
|Median PSA, ng/mL (IQR)||8.03 (5.64–14.26)||9.12 (6.55–15.63)||0.055*|
|Median prostatic volume, mL (IQR)||35 (25–50)||36.5 (27–54)||0.098*|
|DRE findings‡|| || || |
|T1 or T2, number of patients (%)||194 (88.2)||188 (85.5)||0.214†|
|T3 or T4, number of patients (%)||23 (10.5)||32 (14.5)|
Of patients who underwent physician-led TRUSP, 57.3% (126/220) were diagnosed with prostate cancer compared with 52.7% (116/220) in the NPP-led clinic (P = 0.338). When patients were risk stratified according to their presenting PSA levels, there was no difference in the overall cancer detection rates between the NPP and the physician (Table 2). As patients with localized, intracapsular (T1/T2) disease with a PSA level < 9.9 ng/mL have the highest chance of cure and largest number of treatment options, we performed a sub-group analysis to verify whether the cancer detection rates between a physician and an NPP were equal in this sub-group of patients. We found no statistically significant difference in cancer detection rates between the NPP and the physician (P = 0.158).
Table 2. Prostatic biopsy outcomes categorized by prostate-specific antigen risk and operator
|Presenting PSA (ng/mL)||Physician||Nurse||P*|
|<9.9 ng/mL||% cancer detected (number of cancers detected)||47.1 (66)||37.4 (43)||0.117|
| ||Total number of patients seen||140||115|| |
|10–19.9 ng/mL||% cancer detected (number of cancers detected)||66.7 (28)||60.6 (40)||0.525|
|Total number of patients seen||42||66|| |
|>20 ng/mL||% cancer detected (number of cancers detected)||84.2 (32)||84.6 (33)||0.961|
|Total number of patients seen||38||39|| |
We were also particularly interested in evaluating whether a learning curve existed for this procedure, especially as the current series represented the initial experience of the NPP in performing TRUSP independently after completion of her training. When the overall cancer detection rates between the first and the last 100 biopsies performed by each of the TRUSP operators were compared, we found no statistically significant differences in overall cancer detection rates (Table 3a). In a subgroup analysis of men presenting with a low PSA level (<9.9 ng/mL), however, we noted that the NPP had a lower cancer detection rate during her first 100 cases (29.2%, 14/48) compared with the experienced physician at the same institution (50.8%, 32/63, P = 0.022) (Table 3b). This observed difference was no longer seen in the NPP's last 100 cases, suggesting the presence of a learning curve (42.6%, 23/54, P = 0.641). To further investigate this, cancer detection rates of the NPP and the physician were stratified according to procedural case volume (0–50, 51–100, 101–150, 151–200 cases). We found that the NPP required at least 50 independent TRUSP procedures before achieving a cancer detection rate comparable to that of the experienced urologist in men presenting with a low PSA level (<9.9 ng/mL) (Fig. 1).
Figure 1. Cancer detection rates in men presenting with a low prostate-specific antigen level (<9.9 ng/mL) stratified according to transrectal ultrasound-guided prostatic biopsy (TRUSP) case volume. NPP, non-physician provider.
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Table 3. Comparisons of cancer detection rates per operator experience
|% cancer positivity first versus last 100 cases, % (n/N)|
|First 100||60 (60/100)||55 (55/100)||0.474|
|Last 100||57 (57/100)||51 (51/100)||0.395|
|(b) Presenting PSA < 9.9 ng/mL|
|% cancer positivity in low presenting PSA (<9.9 ng/mL) group first versus last 100 cases, % (n/N)|
|First 100||50.8 (32/63)||29.2 (14/48)||0.022|
|Last 100||46.9 (30/64)||42.6 (23/54)||0.641|
We also investigated for significant predictors of positive TRUSP. In univariate accuracy analysis, age (AUC 0.625, P ≤ 0.001), presenting PSA (AUC 0.674, P ≤ 0.001), prostatic volume (AUC 0.634, P ≤ 0.001) and clinical stage (AUC 0.621, P ≤ 0.001) were all highly predictive of a positive biopsy (Fig. 2). A similar pattern was found on multivariate binary logistic regression analysis, where increasing age (odds ratio (OR) 1.054, 95% CI 1.025–1.084), presenting PSA level (OR 1.05, 95% CI 1.02–1.081), prostatic volume (OR 0.969, 95% CI 0.958–0.981) and clinical stage (OR 1.538, 95% CI 1.046–2.261) were all found to be predictive of a positive prostate biopsy. In both analyses, the operator performing the TRUSP was not found to be a significant predictor of positive prostatic biopsies (AUC 0.49, OR 0.729, 95% CI 0.464–1.146, P = 0.171) (Table 4; Fig. 2).
Figure 2. Receiver operating characteristic curves depicting the accuracy of individual predictors of a positive prostatic biopsy. PSA, prostate-specific antigen; TRUSP, transrectal ultrasound-guided prostatic biopsy.
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Table 4. Area under curve and multivariate binary logistic regression analysis of positive prostatic biopsy predictors
|Variable||AUC of individual predictor variables (95% CI)||Binary analysis: OR (95% CI); P-value|
|Age||0.625 (0.572–0.678)||1.054 (1.025–1.084); ≤0.001|
|Presenting PSA||0.674 (0.623–0.725)||1.05 (1.02–1.081); 0.001|
|Prostatic Volume||0.634 (0.582–0.687)||0.969 (0.958–0.981); ≤0.001|
|Clinical Stage||0.621 (0.568–0.674)||1.538 (1.046–2.261); 0.029|
|TRUSP operator||0.49 (0.435–0.545)||0.729 (0.464–1.146); 0.171|
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Reducing waiting times, improving access, enhancing patient journey and satisfaction, improving health outcomes, and provision of good value for money are some of the core principles of an efficient healthcare system. To this end, the use of NPPs such as nurse practitioners has been pivotal in fulfilling the demands of a modern healthcare system. NPPs now provide a large range of protocol-driven multi-disciplinary services within both primary and secondary care settings in the UK and have been shown in a number of studies to be cost-effective, safe and acceptable to patients [2-5]. The concept of NPPs however, is neither new nor unique to the UK. In the USA, for example, physician assistants have been in place since the 1960s, in an effort to address the national shortage of physicians in primary care as well as in rural areas . Across Europe, there are now approximately 2500 Urology nurse practitioners who belong to the European Association of Urology Nurses , providing a diverse range of urological services such as flexible cystoscopy [8-10], lower urinary tract assessment [11, 12], prostate clinics [13, 14] and sexual dysfunction assessment clinics . Although the physician in charge is ultimately responsible for the care of their patients, it is clear that the role of the NPP has evolved and expanded considerably in recent times.
In the present study, we evaluated the performance of a newly trained NPP performing TRUSP independently at a single UK institution. With overall cancer detection rates of 52.9%, we found that there was no difference in the overall cancer detection rates between TRUSP performed by an NPP and a physician (57.3%, P = 0.338). Our observation is in agreement with a previous study performed by Henderson et al. , who evaluated the reliability of TRUSP between nurse practitioners and urologists. The authors reported that the overall cancer detection rates between the nurse practitioners and urologists were similar in patients across all risk groups. In contrast to their study, however, we found that the detection rates of low-risk, low PSA level (<9.9 ng/mL) prostate cancer were lower in the first 50 independent TRUSP performed by the novice NPP compared with the experienced urologist (P = 0.014). This initially observed difference however, was no longer seen as the NPP gained more experience with this procedure (Fig. 1), suggesting the presence of a learning curve.
Although the possibility of a learning curve associated with performing TRUSP (like many other surgical procedures) is perhaps to be expected, the choice of whether or not the operator performing TRUSP, and their experience, actually influences cancer detection rates is a matter of continuing debate. In evaluating whether the training level of urology residents resulted in a difference in prostate cancer detection after TRUSP, Karam et al.  retrospectively analysed the medical records of 627 consecutive patients who had their prostate biopsied by a trainee. The authors found no association between the trainee's residency level (and by implication experience) and prostate cancer detection on TRUSP. It is likely, however, that even the most junior Urology resident has considerable experience in performing TRUSP, because it is an essential skill that needs to be developed rapidly by all trainee urologists. In addition, multiple Urology residents (with perhaps different individual TRUSP experiences) contributed to each biopsy cohort, introducing further bias to their results. In a similar study, Henderson et al.  evaluated the TRUSP cancer detection rates between two NPPs, a trainee urologist and two consultant urologists. Although they reported that both NPPs were able to detect prostate cancer as effectively as consultant urologists, it is unclear whether experience with the procedure influences cancer detection rates because this was not evaluated in the study. On the other hand, Lawrentschuk et al.  reported a significant difference in prostate cancer detection rates between four different, experienced uro-radiologists with an individual median caseload of 514 biopsies. Interestingly, the authors could not identify any changes in cancer detection rates with increasing case volume that mirrored a learning curve. It should be noted, however, that before joining the TRUSP team, all operators were radiologists highly experienced with the use of ultrasound equipment and biopsy procedures , making the identification of a learning curve potentially difficult. In contrast, the NPP in our study was a true novice who had to be trained in all aspects of the TRUSP procedure from the outset.
Our study has a number of implications. To the best of our knowledge, the present study is the largest series evaluating the role of an NPP-led TRUSP service. We found that an adequately trained NPP was able to perform TRUSP as effectively as an experienced urologist after an initial learning curve. Our local institutional policy is for patients with a negative TRUSP to have their PSA level monitored in the outpatient clinic for a minimum of a year, with an increase prompting re-biopsy. Of the first 50 TRUSP cases performed by the NPP, only one of the 18 patients with a PSA level < 9.9 ng/mL and an initial negative biopsy was subsequently diagnosed with prostate cancer (Gleason 6, <1% of a core) on follow-up. Our study therefore highlights the importance of robust clinical governance measures (such as regular audit of biopsy outcomes) to be in place, especially for those units contemplating starting an NPP-led TRUSP service. In addition, although it may seem that the training opportunities for Urology residents may suffer as a consequence of this initiative, we feel that an adequately trained NPP should be just as capable at teaching this essential technique to trainees as a consultant urologist.
The limitations of this study should also be noted. The sequential allocation of patients to a physician or an NPP-led TRUSP clinic by the Cancer Referrals Office may have introduced some selection bias; however, the baseline characteristics of the study cohort were similar across the two TRUSP operator groups (Table 1). In addition, patients allocated to the NPP-led TRUSP clinic were given the choice to refuse and elect to be seen in the physician-led clinic instead. Although none of the patients actually pursued this option, we felt that this choice was appropriate, ethical and in the best interest of patients. We also did not set out to specifically compare the differences in complication rates between an NPP-led and a physician-led TRUSP service. Our internal audit data of TRUSP-related complications, however, has not identified any obvious differences in morbidity between the two TRUSP operators. Nevertheless, subtle differences between the NPP and physician in factors such as post-procedural discomfort and pain remain a possibility. Finally, the current study evaluated the experience of a single novice NPP so further high-quality, multi-institutional, randomised controlled study of NPP-led versus physician-led TRUSP with prospective collection of post-procedural complications is warranted.
In conclusion, an adequately trained NPP is as effective in detecting prostate cancers by TRUSP as an experienced urologist after an initial learning curve of 50 cases. With an increasing trend towards the use of NPPs in protocol-driven procedures, this study highlights the need for a robust TRUSP training programme and clinical governance measures to be in place, especially for Urology units contemplating introducing an NPP-led TRUSP service.