Epidemiology of oral Kaposi’s sarcoma in Zimbabwe 1988-1997: A population-based study

Abstract

Objective: Sub-Saharan Africa has the highest number of HIV/AIDS cases globally which contrasts with the lack of population-based studies of oral Kaposi's sarcoma (OKS); one of the clinical cardinal signs of HIV/AIDS. To date, no study has investigated the incidence of OKS in African populations affected by the HIV/AIDS epidemic. It is, therefore, the purpose of this study to assess the burden of OKS in the Zimbabwean population over a 10 year period. Design: A descriptive epidemiological study was undertaken to assess the burden of OKS by determining the frequencies, incidence and cumulative rates, the lifetime risk and chances of developing OKS according to site (topography), gender, age, race/ethnic origin of the Zimbabwean population. A total of 445 incident cases of OKS from the upper and lower lips, oral vestibule, retromolar area, floor of mouth, tongue, cheek, mucosa, gums, hard and soft palate were accessed from the Zimbabwe National Cancer Registry (ZNCR). Cases from the skin, pharynx, larynx and the major salivary glands were excluded from the study. Setting: This comprised the population of Zimbabwe during the 10 year period 1988-1997. The population figures used for this study were fro the 1992 Census Zimbabwe National Report. The study population was standardized by the direct method against the world standard population to calculate the age standardized incidence rate (ASIR). The SPSS statistical software programme (SPSS Inc. 2001, USA) was used for the statistical analysis. Results: OKS comprised 0.92% of total body malignancies and 51 % of oral malignancies with a mean age of study cases of 37.6 years and median age of 32 years. Histology of the primary (64.5%) and clinical diagnosis (34.6%) were the predominant methods of diagnosis. OKS affected nearly only blacks and males more than females, with a male to female ratio of 1.9:1. The most affected age groups by OKS were the 30 to 34 years for male and 25 to 29 years for both females and the whole population. Other notable peaks in OKS rates were in the 0 to 4 year and the 75+ age groups. OKS mostly affected the palate (70.2%) followed by, in descending order, the tongue (13.3%) and mouth (8.3%). The age adjusted age standardized incidence rate (ASIR) of OKS exponentially increased the entire study period bypassing oral squamous cell carcinoma (OSCC) as the predominant oral malignancy in 1994. Among AIDS-associated malignancies, OKS accounted for 98% while the balance comprised Burkitt’s lymphoma, Hodgkin's and Non-Hodgkin's lymphomas, haemangiosarcoma and lymphoma not specified. Conclusion: OKS was the commonest malignancy of young adults affecting males more than females. OKS steady increased for the entire study period overtaking SCC in 1994 to become the commonest oral malignancy for the remainder of the study period. The palate was the most affected intra-oral site by OKS.