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ORIGINAL ARTICLE
Year : 2016  |  Volume : 19  |  Issue : 1  |  Page : 27-31

A comparative study of the relevance of digital rectal examination, transrectal ultrasound, and prostate-specific antigen in the diagnostic evaluation of patients with advanced carcinoma of the prostate in a resource poor environment


1 Department of Surgery, Ladoke Akintola University of Technology Teaching Hospital, Osogbo, Nigeria
2 Department of Pathology, Ladoke Akintola University of Technology Teaching Hospital, Osogbo, Nigeria
3 Department of Radiology, Ladoke Akintola University of Technology Teaching Hospital, Osogbo, Nigeria
4 Department of Community Health, Obafemi Awolowo University, Ile Ife, Osun State, Nigeria

Date of Web Publication6-May-2016

Correspondence Address:
Oladapo A Kolawole
Department of Surgery, Ladoke Akintola University of Technology Teaching Hospital, Osogbo, Osun State
Nigeria
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DOI: 10.4103/1118-8561.181892

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  Abstract 

Aims: To compare the diagnostic yield of digital rectal examination (DRE), transrectal ultrasound (TRUS) scan, and prostate-specific antigen (PSA) in diagnostic evaluation of advanced carcinoma of the prostate (CAP). Subjects and Methods: A comparative study of sensitivity and specificity of DRE, TRUS, and PSA in the evaluation of advanced CAP. This was done over a 3-year period (January 2010 to December 2012) in a tertiary health institution in Sub-Saharan Africa. All patients presenting with symptoms of prostatic enlargement were recruited, DRE, TRUS, and PSA findings were compared to the histological diagnosis. Statistical Analysis Used: SPSS version 16.0. Results: One hundred and eight cases were analyzed. Histological diagnosis revealed that 52 (48.1%) were CAP whereas 56 (51.9%) were benign. All the patients presented with lower urinary tract symptoms. Surprisingly, some patients with advanced CAP had PSA values in the normal range (0-4 ng/ml) while some with the benign disease also had PSA values above 50 ng/ml. PSA was noted to have the highest sensitivity but lowest specificity. Conclusions: Limitations of PSA are not only seen in screening for early disease, but also in the diagnosis of advanced CAP, and no value of PSA can be considered safe to declare a patient CAP free.

Keywords: Carcinoma, diagnosis, prostate, screening, ultrasound


How to cite this article:
Olajide AO, Eziyi AK, Kolawole OA, Sabageh DO, Ajayi IA, Olajide FO. A comparative study of the relevance of digital rectal examination, transrectal ultrasound, and prostate-specific antigen in the diagnostic evaluation of patients with advanced carcinoma of the prostate in a resource poor environment. Sahel Med J 2016;19:27-31

How to cite this URL:
Olajide AO, Eziyi AK, Kolawole OA, Sabageh DO, Ajayi IA, Olajide FO. A comparative study of the relevance of digital rectal examination, transrectal ultrasound, and prostate-specific antigen in the diagnostic evaluation of patients with advanced carcinoma of the prostate in a resource poor environment. Sahel Med J [serial online] 2016 [cited 2019 Oct 18];19:27-31. Available from: http://www.smjonline.org/text.asp?2016/19/1/27/181892


  Introduction Top


Carcinoma of the prostate (CAP) is currently the most frequently diagnosed cancer among males. [1] Although it was initially thought to be uncommon in Africans, recent studies have shown that the incidence and prevalence rates are higher in Africans than in age-matched African-Americans. The clinical outcome is also known to be relatively poor among blacks who typically present for treatment at advanced stages of the disease and at relatively younger ages. [2]

Before the advent of sophisticated diagnostic techniques, the diagnosis of CAP was mainly done with digital rectal examination (DRE) with the attendant limitations as it was only useful in detecting advanced diseases. Previous studies have also shown that the findings and conclusions reached at DRE were subjective and observer dependent. [3] The subsequent introduction of the transrectal ultrasound (TRUS), which was greeted with much expectation with the hope that it would assist in detecting cancer nodules eluding detection by DRE turned out to be a disappointment. [4] Nevertheless, the introduction of the serum prostate-specific antigen (PSA) test brought about a revolution in the diagnosis of CAP since it allowed the detection of the disease in its early stages. This resulted in a significant reduction in the number of cases of CAP diagnosed at advanced stages. Since then, researchers have concentrated on the merits and demerits of the PSA in the early detection of CAP. [5] In recent times, however, controversies have trailed the use of the PSA in the screening and early diagnosis of CAP since it is becoming apparent that serum PSA estimation has some significant drawbacks in the evaluation of patients with prostatic disorders. [6]

Although a larger percentage of cases of CAP are still being diagnosed at advanced stages in most African nations, only extremely very few studies have examined the role of serum PSA in the management of such cases. [7] This informed our decision to review and compare the diagnostic relevance of these three major diagnostic modalities in the evaluation of advanced CAP, especially in a resource poor country like Nigeria. Thus, the aim of this study was to compare the diagnostic yield of DRE, TRUS scan (TRUSS), and PSA in the diagnostic evaluation of advanced CAP. Our objectives were to determine the proportion of CAP patients presenting with elevated PSA, abnormal DRE and TRUSS findings, and to relate the sensitivity and specificity of these modalities to their yield in the diagnosis of advanced CAP.


  Subjects and methods Top


This was a prospective study aimed at calculating and comparing the sensitivity and specificity of DRE, TRUS, and PSA and to give recommendation(s) as to their continuous use in the evaluation of advanced CAP. This study was conducted over a 3-year period (January 2010 to December 2012) in an urban city in the rain forest belt of South-West Nigeria.

After obtaining ethical clearance from the ethics committee of the hospital, all patients who presented with symptoms and signs of prostatic disease during the study period were recruited into the study. Patients with incomplete clinical records and those who have had some form of treatment for benign prostate enlargement (BPE) or CAP before presentation to our hospital were excluded from the study. The essence of the study was explained and verbal consent obtained from each patient.

The age of the patients and their mode of presentation, including DRE findings were documented at first clinical contact. All DREs for the purpose of the study were done by the attending specialist in urology. Blood was taken for serum PSA, which was done using enzyme-linked immunosorbent assay method in the hospital's chemical pathology laboratory. TRUS was done in each case by a combined team of radiologists and urologists. A prostatic biopsy was performed on all patients with a serum PSA above 4 ng/ml and/or with features suggestive of malignant disease on DRE and TRUS. All patients diagnosed with benign disease had prostatectomy (transurethral resection or retropubic prostatectomy), and the specimens were sent to the histopathology laboratory for histological evaluation. The histology reports of the biopsy and postprostatectomy specimens were documented.

The data obtained were analyzed for the different variables using SPSS version 16.0, (SPSS Incorporated, 2007, Chicago Illinois, USA).


  Results Top


One hundred and twenty-seven patients were seen during the study period. However, only the results obtained from 108 (85.0%) patients were analyzed since 13 (10.2%) of them had been on medical therapy for BPE before presentation while 6 (4.7%) patients had inadequate clinical records at the conclusion of the study. The age distribution of the patients is as shown in [Table 1]. This shows that the highest incidences of prostatic diseases were seen in the 8 th and 7 th decades.
Table 1: Age distribution of patients with prostatic disease


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Histopathological evaluation showed that 52 (48.1%) cases were CAP while 56 (51.9%) cases were BPE. The occurrence of BPE and CAP among different age groups is as shown in [Figure 1] with BPE occurring more commonly than CAP in the 6 th and 7 th decades although CAP becomes more common from the 8 th decade.
Figure 1: Occurrence of carcinoma of the prostate and benign prostatic hyperplasia in different age groups

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All the patients presented with lower urinary tract symptoms of varying severity, and none was diagnosed at screening. Forty-three (82.3%) patients diagnosed with CAP presented with urinary retention (acute or chronic) and needed catheterization while 36 (69.2%) had significant urinary tract infection at presentation and 32 (61.5%) had features of distant metastasis at presentation.

[Figure 2] shows the diagnostic outcome of DRE findings compared with the final histological diagnosis with DRE showing a sensitivity of 73.1% and a specificity of 84.62% in the diagnosis of CAP. [Figure 3] also compares the diagnostic outcomes of TRUS findings with the final histological diagnosis, with TRUS showing a sensitivity of 78.6% and a specificity of 67.5%. Comparison of the diagnostic outcomes of serum PSA and the final histological diagnosis shows a linear relationship between the PSA value and the occurrence of CAP [Figure 4]. Surprisingly, 2 cases (3.9%) of advanced CAP had PSA values <4 ng/ml while 19 (33.9%) patients with benign prostatic hyperplasia had serum PSA values above 20 ng/ml. The sensitivity and specificity of serum PSA at the cut-off levels of 4, 10, 20, and 50 ng/ml were calculated and compared with those of DRE and TRUSS. At 4 ng/ml, PSA has the highest sensitivity and lowest specificity. Increasing cut-off values of serum PSA were associated with a corresponding reduction in its sensitivity and a corresponding increase in its specificity [Figure 4].
Figure 2: Comparison of digital rectal examination findings with histological diagnosis. Sensitivity: 73.1%, Specificity: 84.6%

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Figure 3: Comparison of transrectal ultrasound scan findings with histological diagnosis. Sensitivity: 78.6%, Specificity: 67.5%

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Figure 4: Comparison of prostate-specific antigen values with histological diagnosis

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  Discussion Top


BPE and CAP remain common disorders of the prostate, especially in our environment. The highest incidences for both BPE and CAP in this study were in the 8 th decades of life although BPE was relatively more common than CAP before the 8 th decade of life. This trend was reversed after the 8 th decade. This finding is similar to reports from other parts of Nigeria and Africa at large. [7] "Late detection" has been the normal pattern of presentation of CAP in most African nations. [7],[8] No early case of CAP was detected at screening; rather, various degrees and types of complications were observed at presentation. This may be partly due to the fact that CAP in Black Africans is typically associated with a rapid rate of progression as well as an initially high Gleason's score although it may just be the result of peculiar cultural and religious practices including persistent beliefs in faith healing and traditional/alternative medicine, which result in late presentation to the hospital for treatment. [8]

DRE is in most parts considered undesirable in the evaluation of CAP because it is predominantly useful in the diagnosis of advanced prostatic carcinoma even though a significant proportion of patients with DRE findings suggestive of malignancy turn out to be negative for malignancy after histological evaluation. [9] Despite these facts, DRE has remained an important modality in the diagnosis and staging of patients with CAP. In this study, although DRE had the lowest sensitivity, it had the highest specificity when compared to TRUS and PSA. Similar findings have been reported in other studies comparing the diagnostic relevance of DRE, TRUS, and PSA. [10] This seems to suggest that DRE still plays an important role in the diagnostic workup of patients with CAP. Indeed, quite a few studies have shown that DRE is very useful in the screening of patients with PSA values within the normal range. In a recent study, 23% of men with normal PSA (<4 ng/ml) were diagnosed with CAP based only on the findings at DRE. [11] In another study, about 18% CAP was detected by DRE alone irrespective of the PSA values. [12] This study, like others before it, therefore, shows that DRE remains a very useful tool for the urologists, especially in most parts of Sub-Saharan Africa where there are no organized screening programs or advanced diagnostic tools, and most patients present late to the hospital with advanced disease.

The earlier introduction of TRUS as a screening tool for CAP was marred by its low sensitivity and specificity; therefore, it is no longer used as a screening modality for CAP. In fact, its use as a screening tool has since been abandoned in the United States and Europe, not least because of its cost and the stress of the procedure. [13] Our findings, however, show that TRUS has a sensitivity close to that of PSA but higher than that of DRE as well as a specificity close to that of DRE, but higher than that of PSA. Typical ultrasound findings seen in our patients include hypoechoic nodules, asymmetry of the prostate gland, heterogeneous echotexture, increased vascularity, and breach of the capsule. Although TRUS may no longer be relevant in the screening of early prostatic malignant disease, it may still be relevant in diagnosis of advanced CAP in resource-poor environments like ours since the features of malignancy as previously outlined are clearly obvious and distinct. In advanced disease, TRUS guidance will also lead to a reduction in the number of biopsies taken and improve the sensitivity of prostate cancer detection as biopsy specimens are then taken directly from the lesions seen. [13]

Several controversies have trailed the continued use of PSA in the screening and diagnosis of CAP. Indeed, the normal reference values have been changed in some parts of the world from the traditional 0-4 ng/ml to much lower values. [6],[14] Thus, in the screening procedure for early prostate cancer, the optimal cut-off value for serum PSA is yet unknown. The ineffectiveness of serum PSA as it is currently being used in the evaluation of patients with prostatic disease has led to an increase in the number of biopsy specimens taken from the prostate from about 6 to 12 all in an attempt to increase the diagnostic yield of the procedure. Moreover, several studies have also shown that high-grade CAP can occur in men with a serum PSA as low as 0.6-1 ng/ml. [14] As expected, our findings show a linear relationship between the PSA value and the number of patients diagnosed with CAP. This is a significant finding, which further confounds the controversies surrounding the use of PSA in the evaluation of patients with enlarged prostates, as our study showed that patients with advanced CAP whose serum PSA was within the "normal reference value of 0-4 ng/ml" constituted 3.9% of all our patients with histologically confirmed CAP. This proportion rose to 17.6% for PSA values of 10 ng/ml. These findings further buttress the fact that the serum PSA correlates poorly with the stage or severity of CAP and, thus reiterate the need always to include other screening modalities in the evaluation of patients with enlarged prostates including those with suspected advanced CAP.

In one previous study, it was noted that setting the normal limit of serum PSA at 4ng/ml led to the inadvertent diagnostic exclusion of over 80% of cases of CAP in young men and 65% of cases in old men. [15] Although serum PSA was the most sensitive of the three modalities used in this study at 4 ng/ml, its specificity was the lowest. This will, therefore, result in high number of cases with false positive values as well as a large number of cases for which unnecessary prostatic biopsies are performed. On the other hand, however, increasing the upper limit of the reference value will improve the specificity at the expense of the sensitivity, causing a high proportion of cases with false negative values. The reverse is the case for DRE, which has a high specificity and low sensitivity. Similar findings have been reported from other studies. [15] Despite these shortcomings, however, the application of PSA density, PSA velocity, and age-specific PSA may improve the specificity of serum PSA, thereby reducing the percentage of false positives and preventing unnecessary prostate biopsies although these parameters may be unhelpful when the PSA values fall with normal limits.

It is becoming clearer that serum PSA, as it is being used presently, has a lot of drawbacks, and no value of serum PSA can be considered safe to declare a patient CAP free. The use of a combination of these three diagnostic modalities in the evaluation of patients with the prostatic disease and, indeed CAP will remain the best practice until better diagnostic modalities are available, especially in resource-poor countries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Ajape AA, Ibrahim KO, Fakeye JA, Abiola OO. An overview of cancer of the prostate diagnosis and management in Nigeria: The experience in a Nigerian tertiary hospital. Ann Afr Med 2010;9:113-7.  Back to cited text no. 7
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Song JM, Kim CB, Chung HC, Kane RL. Prostate-specific antigen, digital rectal examination and transrectal ultrasonography: A meta-analysis for this diagnostic triad of prostate cancer in symptomatic Korean men. Yonsei Med J 2005;46:414-24.  Back to cited text no. 10
    
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Richie JP, Catalona WJ, Ahmann FR, Hudson MA, Scardino PT, Flanigan RC, et al. Effect of patient age on early detection of prostate cancer with serum prostate-specific antigen and digital rectal examination. Urology 1993;42:365-74.  Back to cited text no. 12
    
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Terris MK, Freiha FS, McNeal JE, Stamey TA. Efficacy of transrectal ultrasound for identification of clinically undetected prostate cancer. J Urol 1991;146:78-83.  Back to cited text no. 13
    
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Krumholtz JS, Carvalhal GF, Ramos CG, Smith DS, Thorson P, Yan Y, et al. Prostate-specific antigen cutoff of 2.6 ng/mL for prostate cancer screening is associated with favorable pathologic tumor features. Urology 2002;60:469-73.  Back to cited text no. 14
    
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