A REVIEW OF THE AETIOLOGY OF SQUAMOUS CELL CARCINOMA OF THE CONJUNCTIVA, WITH PRELIMINARY RESULTS OF A CASE-CONTROL STUDY FROM KAMPALA, UGANDA

Abstract

Although rare in Europe and the USA, the incidence of squamous cell carcinoma of the conjunctiva increases by almost 50% with each 10° decline in latitude(P<0.0001) and it is known to be caused by exposure to solar ultraviolet light. Furthermore, 3 studies from Africa and one from the USA have demonstrated an association with HIV infection(summary odds ratio=13.0; 95% confidence intervals=7.2-23.1; derived from weighted averages of the log relative risks from each study). Human papilloma viruses may also be involved in the aetiology of conjunctival squamous cell carcinoma although results from twelve published studies are conflicting. In an on-going study of the relationship between HIV infection and cancer, in Kampala, Uganda, an attempt is being made to interview and HIV test all cancer patients within the 5 main city hospitals. Since August 1994, 71 patients with squamous cell carcinoma of the conjunctiva have been recruited, and asked about various social and lifestyle factors. The comparison group comprises over 1200 patients with all cancers other than Kaposi's sarcoma and non-Hodgkin's lymphoma (which are known to be HIV-associated), for whom questionnaire data and HIV test results are available. Tissue specimens are also collected, a sample of which are being tested for the presence of Human papilloma viruses. To date, over 70% (45/63 tested) of those with conjunctival squamous cell carcinoma were HIV seropositive compared to less than 20% of the comparison group (odds ratio 8.3; 4.5-15.5, adjusted for age and sex). No other consistent associations have yet been observed although numbers are small at the moment. Data on HPV in tumour tissue are awaited. These preliminary results confirm the known association of squamous cell carcinoma of the conjunctiva with HIV infection, but more cases are required before other possible risk factors can be considered in detail. Thus, together with Kaposi's sarcoma and non-Hodgkin's lymphoma, squamous cell carcinoma of the conjunctiva is the third tumour to be clearly HIV-associated.