Prostate specific antigen as a risk factor for skeletal metastases in black African men with prostate cancer

Date of Award


Document Type


Degree Name

Master of Medicine (MMed)

First Supervisor/Advisor

Khalid B. Makhdomi

Second Supervisor/Advisor



Imaging and Diagnostic Radiology (East Africa)


Background: Prostate cancer is one of the commonest cancers in men worldwide. Several recognised risk factors are associated with this disease, amongst them, race. Despite this, there is a paucity of data in the native African setting. The skeletal system is a common site of metastasis, its incidence increasing with increase in prostate specific antigen (PSA) levels. Bone scans are used to detect skeletal metastases. Its use in prostate cancer patients with abnormal but low PSA has been subject of debate.

Objectives: To test the association of PSA levels with skeletal metastasis in men with histologically proven prostate cancer.

Methodology: Case control study. Using Radiology and Pathology records, a registry of prostate cancer patients recorded as being of Black African ethnicity previously investigated in the institution was assembled. Following anonymisation and coding, archive images were presented to a nuclear physician blinded to the PSA level, to determine presence and sites of skeletal metastases. The risk factor for the outcome of interest (skeletal metastases) was PSA level above 20ng/ml. The reliability of image reporting for bone scans was also analysed.

Results: Of 122 patients, 50 (41%) had skeletal metastases, while 72 (59%) had no skeletal metastases. The prevalence of metastases among the high PSA group was 55.9% (44.1% to 67.7%) and 22.2% (11.1% to 33.3%) among the normal/low PSA group. The Odds Ratio (OR) for skeletal metastases in the exposed group was 4.4 (95% CI, 2.01 – 9.78.) There was an intra-observer agreement of 88.5% with a Kappa statistic of 0.76. Inter observer agreement was 85.3% (Kappa statistic of 0.70.)

Conclusion: Significantly higher prevalence of skeletal metastasis is seen in regional Black African males with prostate cancer, at both low and high PSA levels. Bone scanning in this population should therefore be considered even at PSA levels below 20ng/ml.

This document is available in the relevant AKU library