Insufficient data exist on prostate cancer in the West African subregion in spite of the huge burden of the disease. This made it difficult to establish guidelines for its management. In Nigeria, available data are from the urban centers and are mostly on incidence and prevalence of the disease [8, 9].
DRE is a veritable tool in the diagnosis of carcinoma of the prostate. The features on DRE which may arouse the suspicion of carcinoma of the prostate are an enlarged prostate, suspicious nodule, hard nodular prostate, lobar asymmetry, the presence of indurations and obliteration of the median groove. The sensitivity of DRE is poor and is estimated to be 53–59%, while the specificity is 83–94%. The positive predictive value has been placed at 18–20%. Data available indicate that the PSA level is as effective as or more effective than DRE for detection of prostate cancer [10]. This explains the stronger significant correlation between PSA and histology (P = 0.000) than between DRE findings and histology (P = 0.005) in this study. The high PPV of 66.5 documented here for DRE can be explained by the phenomenon of late presentation in this environment at a time the features of the disease are usually obvious on DRE.
The various findings which sum up to constitute abnormal DRE findings were handed down decades ago, and their value does not seem to have been validated in our region. In this study, a hard nodular prostate, with a positive predictive value (PPV) of 73 (Table 2), appears to be the only independent finding that strongly predicts the risk of adenocarcinoma. This PPV is lower than the 81 documented for DRE by Walsh et al. [6]. Apart from a hard nodular feel, the others apparently need to be evaluated in association with other variants or combined with a PSA assay to enable a decision to biopsy in order to minimize negative biopsies. This assertion can be buttressed with the PPV of a suspicious nodule, obliterated median groove and lobar asymmetry (Table 2).
A suspicious nodule in the prostate may result from previous biopsy, prostatitis, benign prostatic hyperplasia, prostatic calculi and malignancies of the prostate. Of the 26 men who had a suspicious nodule in the prostate as a sole finding in this study, only 6 (23.1%) had adenocarcinoma giving a PPV of 23.1 despite the additional targeted biopsies. In the work of Lopes et al. [11] out of 34 men with suspicious nodules, 25 (74%) were, however, adenocarcinoma, a sharp contrast to our finding. This may be a regional, racial or interobserver difference probably related to the differences in prevalence of the above-mentioned cofounders.
Lobar asymmetry was a sole abnormality in one (0.8%) of the participants of which the histology was nodular hyperplasia giving a PPV of 0%. Though this figure is too low to enable a fair conclusion, it is doubtful whether lobar asymmetry occurring alone should be an indication for prostate biopsy in the presence of a normal PSA. This opinion is similar to that of Hansen et al. [12] who documented a PPV of 25 for lobar asymmetry and therefore concluded that this finding on DRE is not associated with significant increase in cancer detection when compared to normal prostate. Finding of lobar asymmetry on DRE has a high potential for subjectivity and needs to be verified by trans- rectal ultrasonography.
According to Thompson et al. [13], there is no absolute lower value of PSA below which there is no risk of prostate cancer. They also documented that PSA is a marker whose values reflect a continuum of risk for prostate cancer. This is corroborated by this study in which 33.3% of men with PSA between 0 and 4 ng/ml had histologically proven adenocarcinoma while 10.2% of them with a PSA above 50 ng/ml had histological nodular hyperplasia.
Increasing age has been known to be a risk factor for carcinoma of the prostate [14] with a peak incidence often documented to be in the seventh decade of life [15, 16].This is in contrast to this study in which the peak incidence was in the 8th decade of life. This difference may be accounted for by late presentation which is common in this low resource setting [17, 18] compared to the developed world where most are currently commonly screen detected at an early stage and age, raising the fear of over diagnosis and over treatment [6, 19, 20]. This late presentation is also reflected in the high Gleason score in this study, indicating that most of these men presented with advanced disease. This is presently the norm in Sub-Saharan Africa [21, 22]. The peak age incidence is, however, similar to that documented by Albasri et al. [23] and Obiorah et al. [24].
The limitation of this study is in the number of participants which is low considering the burden of the disease in this region. Secondly, digitally guided transrectal biopsy technique was used though this was premised on the fact that DRE was being studied. The participants were more of a cohort of men with late disease, implying that this study cannot be generalized to early prostate cancer. Hopefully, phase 2 of this study may resolve these limitations though this study has been able to throw some light on the value of DRE and its variants in our environment.
