Abstract
Arab Journal of Urology (2014) 12, 256–261 Arab Journal of Urology (Official Journal of the Arab Association of Urology) www.sciencedirect.com ORIGINAL ARTICLE Predicting the resected tissue weight from a digital rectal examination and total prostate specific antigen level before transurethral resection of the prostate Ahmed M. Harraz, Ahmed El-Assmy , Mohamed Tharwat, Ahmed M. Elshal, Ahmed R. El-Nahas, Tamer S. Barakat, Mohamed M. Elsaadany, Samer El-Halwagy, El Housseiny I. Ibrahiem Urology and Nephrology Center, Mansoura University, Mansoura, Egypt Received 9 April 2014, Received in revised form 29 August 2014, Accepted 18 September 2014 Available online 11 November 2014 KEYWORDS Abstract Objective: To determine the use of the prostate specific antigen (PSA) level and digital rectal examination (DRE) findings to estimate the resected tissue PSA; weight (RTW) before transurethral resection of the prostate (TURP). TURP; Patients and methods: We retrospectively analysed 983 patients who underwent Prostate volume; TURP between December 2006 and December 2012. The primary outcome was Resected tissue weight; the RTW required for clinical improvement, and was not associated with re-inter- DRE vention. Age, PSA level, body mass index (BMI) and DRE findings were correlated and modelled with the RTW. The DRE result was defined as DREa (small vs. large) ABBREVIATIONS or DREb (small vs. moderate vs. large) according to the surgeon’s report. Equations AUC, area under the to calculate RTW were developed and tested using receiver operating characteristic curve; (ROC) curve analyses. BMI, body mass index; Results: There were significant correlations between PSA level (r = 0.4, ROC, receiver operat- P < 0.001) and RTW, whilst BMI and age showed weak correlations. The median ing characteristic; (range) RTW was 45 (7–60) vs. 15 (6–60) g for small vs. large prostates (DREa) Corresponding author. Tel.: +20 50 2262222; fax: +20 50 E-mail address: a_assmy@yahoo.com (A. El-Assmy). Peer review under responsibility of Arab Association of Urology. Production and hosting by Elsevier http://dx.doi.org/10.1016/j.aju.2014.09.006 2090-598X ª 2014 Arab Association of Urology. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Estimation of TURP-resected tissue weight 257 RTW, resected tissue (P < 0.001), respectively. Similarly, the median (range) RTW was 11 (6–59) vs. 26.2 weight; (6–60) vs. 42 (7–60) g in small vs. moderate vs. large prostates (DREb) (P< 0.001), PV, prostate volume respectively. Using PSA level and DREb (model 3) there was a significantly better ability to estimate RTW than using PSA and DREa (model 2) or PSA alone (model 1) based on ROC curve analyses. The equation developed by model 3 (RTW = 1.2 + (1.13 · PSA) + (DREb · 9.5)) had a sensitivity and specificity of 82% and 71% for estimating a RTW of >30 g, and 84% and 63% for estimating a RTW of >40 g, respectively. Conclusions: The PSA level and DRE findings can be used to predict the RTW before TURP. ª 2014 Arab Association of Urology. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/3.0/). Introduction Patients and methods Although new technologies are increasing dramatically After obtaining internal review board approval, we ret- TURP continues to be the referent for all procedures rospectively reviewed our electronic databases for treating obstructive LUTS in men. Before surgery an patients who underwent surgery for obstructive LUTS estimation of prostatic volume (PV) is mandatory as it related to BPH between December 2006 and December is related to disease progression, unfavourable outcomes, 2011 and who had completed P6 months of follow-up surgical guidance and is a good estimate of the response (983 men). Only patients who had a standard monopo- to surgery [1,2]. The most reliable method to calculate lar TURP were included. Patients were excluded if they PV is by TRUS [3,4]. Nevertheless, there are many con- had undergone any surgical procedure other than cerns about the results of TRUS. It has been shown that TURP (37) and those with missing data for PSA or the measured PV can vary with the experience of the RTW (207). For the purpose of obtaining an homoge- operator, the size of the prostate and the presence of a nous data distribution, patients with a PSA level of third lobe [5,6]. In addition, conventional bi-dimensional >20 ng/mL (31) and a RTW of >60 (18) were also ultrasonography has been shown to be less accurate than excluded. All patients with a preoperative PSA level of three-dimensional ultrasonography [6]. >4 ng/mL had biopsy-confirmed BPH before surgery. The relationship between PSA level and TRUS- For each patient the electronic database was reviewed measured PV was assessed in many previous publica- for their demographics, including, age, presentation, tions. This strong relationship was confirmed in patients associated medical comorbidity and BMI. Each patient in China [7], Korea [8,9], Taiwan [10] and Netherlands had a DRE before TURP, carried out by the surgeon. [11]. Even in a large population of patients undergoing The approximate size of the prostate was reported as screening, PSA levels correlate well with the PV mea- ‘mild enlargement’ if the size was the same as the distal sured by a DRE [12]. In addition, recently the metabolic phalanx of the index finger, ‘marked’ if the boundaries syndrome and obesity have been shown to influence could not be felt digitally, and ‘moderate’ for any other both PSA levels and PV to a great extent [13–16]. There- sizes. Preoperative laboratory investigations included fore, it was suggested that for an accurate estimation of measurements of the preoperative total PSA, serum cre- PV, PSA measurements and obesity indices should be atinine and haemoglobin levels. A flow curve and post- included [13,17]. void residual urine volume were routinely assessed TRUS-based measurements of PV have shown a before surgery. The TRUS-measured PV was not rou- strong correlation with resected tissue weight (RTW) tinely obtained in every patient. [18,19], as during TURP only adenomatous tissue is All patients underwent a standard monopolar TURP, resected. Although the RTW might not be an indicator with documented resection of most of the adenomatous of the degree of clinical improvement after TURP [20],it tissue. Patients with documented tunnelling only or with might be an indicator of further prostatic growth and incomplete removal of the adenoma were excluded. the need for re-treatment [21,22]. Furthermore, predict- After resection the removed adenomatous tissue was ing the RTW might aid adequate surgical planning compressed and immediately weighed before being before surgery. As there are no previous studies that examined histopathologically. Patients were maintained have correlated PSA level or obesity indices with on quinolone antibiotics for 2 weeks after removal of the RTW, in the present study we determined the utility of urethral catheter. To confirm any clinical improvement, preoperative variables for estimating the RTW before all patients had their postvoid residual estimated and a TURP. flow curve assessed at least once during the follow-up. 258 Harraz et al. an equation to estimate the RTW. As the DRE was Table 1 Demographics for the 693 patients undergoing reported to be associated accurately with large prostates TURP. of >50 g [23], the DRE category was entered twice in Variable Mean (SD) or n (%) two different models together with PSA level, after com- Age (years) 65 (7.3) bining mild and moderate prostates as ‘small’ vs. ‘large’ Presentation prostates (DREa), and as ‘mild, moderate’ vs. ‘marked LUTS 549 (79.2) enlarged’ prostates (DREb). The predicted values of Catheterised 119 (17.2) the derived equations were compared with the actual Haematuria 25 (3.6) values of RTW at different thresholds using the receiver Diabetes mellitus 82 (11.8) operating characteristic (ROC) curve. Hypertension 181 (26) BMI (kg/m ) 28.2 (4.7) PSA (ng/mL) 4.5 (3.9) Results Preop haemoglobin (g/dL) 13.8 (1.6) DRE In all, 693 patients met the study inclusion criteria Mild 287 (41.4) within the specified period. The patients’ demographics Moderate 370 (53.4) are shown in Table 1. The RTW showed no correlation Marked 32 (4.6) with age (r = 0.07, P= 0.05) or BMI (r = 0.07, Not reported 4 (0.5) Vesical stones 121 (17.5) P= 0.04), but there was a moderately positive signifi- Postop haemoglobin (g/dL) 12.7 (4.5) cant correlation with PSA level (r = 0.4, P< 0.001). RTW (g) 22 (13) The median (range) RTW was significantly higher in patients with large vs. small prostates (DREa), at 45 (7–60) g vs. 15 (6–60) g, respectively (P < 0.001). Simi- The primary outcome was the RTW that was associated larly, the median RTW differed significantly between with alleviating obstructive LUTS and that was not small vs. moderate vs. large prostates (DREb), at 11 associated with further prostatic re-intervention at least (6–59) vs. 26.2 (6–60) vs. 42 (7–60) g, respectively within the 6 months after surgery. Therefore, any (P < 0.001). Therefore, equations to estimate the patients requiring re-intervention for residual adenoma RTW were developed based on three regression models within the next 6 months were excluded (seven). using preoperative PSA level alone as a predictor (model 1), PSA and DREa (model 2), and PSA and DREb Statistical analysis (model 3) as predictors (Table 2). Model 1 explained only 16.4% of the variance of RTW values whilst adding The correlation between age, serum PSA level, BMI and DRE findings increased the predictive ability of the RTW was investigated using the Pearson correlation model to 29% and 34% for models 2 and 3, respectively. coefficient. The median RTW was compared between After constructing ROC curves for the three models subcategories of DREa and DREb using the Mann– (Fig. 1A and B), the model 3 equation showed the best Whitney U-test and Kruskal–Wallis test, respectively. predictive ability for a RTW of >30 g, with an area Variables showing a significant correlation with RTW under the curve (AUC) and 95% CI of 0.8 (0.790– were entered into a linear regression model to construct Table 2 Linear regression models for predicting RTW after TURP. Independent variables Coefficient SE r tP partial Model 1 Constant 15.708 PSA 1.400 0.120 0.405 11.64 <0.001 Equation: RTW = 15.708 + (1.400 · PSA) Model 2 Constant 3.792 PSA 1.315 0.115 0.401 11.452 <0.001 DREa 19.037 2.161 0.319 8.810 <0.001 Equation: RTW = (1.315 · PSA) + (19.037 · DREa) 3.792 DREa: small = 1 and large = 2 Model 3 Constant 1.239 PSA 1.133 0.109 0.368 10.379 <0.001 DREb 9.534 0.715 0.453 13.342 <0.001 Equation: RTW = 1.239 + (1.133 · PSA) + (DREb · 9.534) DREb: small = 1, moderate = 2, large = 3 Estimation of TURP-resected tissue weight 259 Table 3 Comparison of the ROC curves of models predicting RTW from PSA level and DRE. RTW AUC SE 95% CI P RTW >30 g Model 1 (PSA) 0.720 0.022 0.685–0.754 <0.001 Model 2 0.756 0.021 0.723–0.788 <0.001 (PSA + DREa) Model 3 0.821 0.017 0.790–0.849 <0.001 (PSA + DREb) RTW > 40 g Model 1 (PSA) 0.702 0.031 0.666–0.736 <0.001 Model 2 0.773 0.029 0.740–0.804 <0.001 (PSA + DREa) Model 3 0.803 0.025 0.771–0.832 <0.001 (PSA + DREb) the difference in areas between models 2 and 3 was 0.029 (0.003–0.062) (P = 0.08). Table 3 shows the results of the ROC curves. Discussion The RTW and not the total PV is the actual determinant of operating time and consequently it is directly related to the perioperative complication rates [24]. Therefore, predicting the RTW might be important in surgical planning before TURP. In the present study there was a moderately significant positive correlation between the preoperative serum PSA level and DRE, and the RTW after TURP, whilst age and BMI had very weak correlations. In addition, adding the DREb gave a sig- nificantly better performance of the model for estimat- ing the RTW than using PSA alone or PSA and DREa as predictors. The relationship between age, total PSA level, obesity indices and TRUS-measured PV was reported previ- ously [14,25]. Nevertheless, age and BMI were weakly correlated with RTW in the present study. During TURP only obstructing adenomatous tissue is removed, with sparing of the peripheral and prostatic capsular tis- sues. Therefore, this eliminates to a major extent the Figure 1 ROC curves for the three models for (A), estimating a effect of age and BMI on PV. Furthermore, as the RTW of >30 g, and (B), of >40 g. RTW is not necessarily correlated with PV, the expected effect of age and BMI is reduced. 0.849) (P< 0.001), with a sensitivity of 82% and speci- Although a preoperative estimation of PV is essential, ficity of 71% at a threshold estimated RTW of >23.5 g. there is a debate as to whether the total PV is an indica- On comparing the three models, the difference between tor of how much tissue should be resected during the areas of model 1 and 2 (95% CI) was 0.036 (0.013– TURP. Park et al. [21] compared 85 patients with a 0.058) (P = 0.001), and the difference between models 2 mean PV of 59.7 g and mean RTW of 11.2 g vs. 178 with and 3 (95% CI) was 0.064 (0.04–0.089) (P < 0.001). a mean PV of 69.9 g and mean RTW of 24 g. Hakenberg Similarly, the model 3 equation had significantly the et al. [20] reported 138 men who underwent TURP, in best predictive ability when compared to models 1 and whom the mean PV was 49 g and the mean RTW was 2 for estimating a RTW of >40 g, with an AUC of 24.7 g. However, the RTW was shown to correlate sig- 0.8 (0.771–0.832) (P< 0.001), with a sensitivity of nificantly with transitional zone volume as measured 84% and specificity of 63% at the same threshold value. by TRUS. Aus et al. [24] reported a significant positive On comparing models 1 and 2, the difference (95% CI) correlation between the RTW and transitional zone vol- between areas was 0.071 (0.028–0.114) (P = 0.001), and ume before and after TURP. In another report, Alkan 260 Harraz et al. et al. [19] described a strong correlation between the esti- equations and hence further validation is required. mated and resected volumes. Milonas et al. [18] com- Finally, our equation did not account for surgeon vol- pared the RTW of adenomas removed by TURP and ume, as an experienced surgeon can resect more tissue open prostatectomy with corresponding TRUS mea- than a trainee. Nevertheless, the study described the surements, found a strong correlation between adeno- experience of TURP over a 6-year period and therefore mas enucleated during open prostatectomy, with a it was difficult to assess the accurate volume for each weak correlation with adenomas removed by TURP. surgeon. Another issue to be addressed is how much RTW is However, to the best of our knowledge this is the first needed to achieve a clinical improvement. Hakenberg reported study to correlate the RTW with preoperative et al. [20] correlated the RTW with the clinical outcome variables. We believe that the findings of the current as measured by symptom scores after TURP, and found study might be beneficial in clinical practice to allow that the RTW was negatively correlated with symptom an approximate estimate of the RTW before TURP, scores, and that there was no significant correlation and therefore aid better surgical planning for optimising between the ratio of RTW to PV and the change in the outcome of the procedure. symptom scores. The authors declared that early symp- In conclusion, the RTW can be predicted from PSA tomatic improvement was dependent on the RTW, but level before TURP, and this prediction is improved after the relationship was weak because of possible other con- adding the finding of a DRE. These equations could be founding variables. They also admitted that the com- used for better surgical planning before TURP. Further pleteness of resection is not mandatory for the studies are needed to validate these findings. optimum clinical outcome. 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Journal
Arab Journal of Urology
– Taylor & Francis
Published: Dec 1, 2014
Keywords: PSA; TURP; Prostate volume; Resected tissue weight; DRE; AUC, area under the curve; BMI, body mass index; ROC, receiver operating characteristic; RTW, resected tissue weight; PV, prostate volume
