Prognostic Significance of Ki67 Expression in Prostate Cancer in Nigerians: A Single-Center Study.

Introduction Prostate cancer is one of the most common cancers occurring in men and one of the leading causes of cancer deaths globally. Associated risk factors include age, race, and positive family history. Older patients have an increased risk for more aggressive forms. Its incidence is particularly high in Black men. The Gleason grading and scoring system is an established prognostic factor for prostate cancer. Ki67, a nuclear protein, coded for by the MKi67 gene located on chromosome 10q26.2 and detected in all phases of the cell cycle, provides information on the proliferation index of cancer cells, including prostate cancer. This study is purposed to establish the significance of Ki67 expression as a prognostic marker of prostate cancer by correlating it with patients' age and Gleason scores, respectively, with the aim of understanding the molecular characteristics of prostate cancers in our environment, in order to assist in categorizing patients for treatment. Materials and methods This was a retrospective study carried out in Jos University Teaching Hospital (JUTH), Jos, Nigeria, involving histologically diagnosed prostate cancers over a five-year period. The surgical pathology reports and information on patients' biodata and clinical features were retrieved from departmental records and the hospital's electronic records. The appropriate archival hematoxylin and eosin (H&E)-stained slides and their respective formalin-fixed paraffin-embedded (FFPE) tissue blocks were retrieved and reviewed, with new sections made when necessary. Immunohistochemical analysis to assess the Ki67 proliferative index was carried out on sections made from representative blocks of each case using Ki67 monoclonal antibodies, according to the established protocol prescribed by the manufacturers. The Ki67 proliferative index was categorized as negative, low, and high. Data obtained were analyzed, and results were presented as percentages/frequencies and displayed as tables and charts. Results One hundred forty-two cases met the inclusion criteria. The age range was 30-90 years. The peak age group was 70-79 years with 38% (54/142). Majority, 81.7% (117/142), of cases occurred in patients above 60 years old. An overwhelming majority, 71.8% (102/142), of cases were poorly differentiated adenocarcinomas (Gleason scores 8-10), 21.1% (30/142) were moderately differentiated (Gleason score 7), and 7.0% (10/142) were well-differentiated (Gleason score 6). Among high Ki67 proliferative index cases, 81.4% (57/70) were aged above 60 years. Similarly, 85.1% (40/47) of low proliferative index cases were also aged above 60 years. Additionally, 92.5% (37/40) of well- and moderately differentiated cancers (Gleason scores 6 and 7) had negative or low Ki67 proliferative indices, while 65.7% (67/102) of the poorly differentiated (Gleason scores 8-10) had high indices. Conclusion Our study demonstrated a direct correlation of the Ki67 proliferative index with both histologic grade and aggressiveness of prostate carcinoma in a Nigerian population thereby confirming high Ki67 proliferative index as an adverse prognostic factor in prostate cancer. It, however, showed no direct relationship between age and Ki67 proliferative index. Determination of the Ki67 proliferative index is recommended for routine assessment of prostate cancer patients to help in risk stratification and instituting treatment plans.