The burden of oral malignancies in Zimbabwe 1988 to 1997: a population based study

Annual reports from the few cancer registries in Africa are the only reliable assessment of the burden of cancer using population-based data. Similar reports for oral malignancies have not been undertaken. The purpose of this study was to assess the burden of oral malignancies in Zimbabwe over a 10 year period using population-based data.

A descriptive epidemiological study was undertaken to assess the burden of oral malignancies by determining the frequencies, incidence and cumulative rates, the lifetime risk and chances of developing an oral malignancy according to site (topography), gender, age, morphology and race/ethnic origin of the Zimbabwean population. A total of 873 incident cases of oral malignancies 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.

This comprised the population of Zimbabwe during a 10 year period 1988 to 1997. The population figures used for this study were from the 1992 Census Zimbabwe National Report. The study population was standardised by the direct method against the world standard population to calculate the age standardized incidence rate (ASIR). The SPSS statistical software program (SPSS Inc.2001, USA) was used for the statistical analysis.

Oral malignancies comprised 1.8% of total body malignancies with high histological confirmation of the diagnosis (77.3%). The 25 to 29 and 30 to 34 five-year age groups were the most and equally affected by oral malignancies. The mean age was 43.9 years and median age was 41 years [standard deviation (SD) = 17.7] excluding 53 cases of'unknown age'. Oral Kaposi's sarcoma (OKS) and oral squamous cell carcinoma (OSCC) were the predominant forms of oral malignancy. The palate was the most commonly affected site by oral malignancy followed by, in descending order, the tongue, mouth, floor of mouth and the gum. Blacks were affected more than whites and males more than females (sex ratio = 1.97:1). The palate and the tongue were the most commonly affected sites in blacks and whites respectively. OKS affected mostly young adults while OSCC was the commonest malignancy of the elderly. The tongue had more OSCC (60.4%) than OKS (31%).

Lip cancer was three times more common in whites than in blacks and affected mostly the elderly, though females irrespective of race had a higher lifetime risk for malignancy of the lower lip. The high incidence of OKS among young adults was due to the HIV/AIDS epidemic.