Decreasing incidence of conjunctival squamous cell carcinoma in people with HIV in South Africa

Abstract

BACKGROUND The main risk factors for squamous cell carcinoma of the conjunctiva (SCCC) are immunodeficiency and exposure to ultraviolet radiation. Little is known about the SCCC epidemiology among people with HIV (PWH) in South Africa. METHODS We used data from the South African HIV Cancer Match study, a nation-wide cohort of PWH in South Africa, created through a privacy-preserving probabilistic record linkage of HIV-related laboratory records from the National Health Laboratory Service and cancer records from the National Cancer Registry from 2004-2014. We calculated crude incidence rates, analyzed trends using Joinpoint models and estimated hazard ratios (HR) for different risk factors using Royston-Parmar flexible parametric survival models. FINDINGS Among 5,247,968 PWH, 1,059 incident SCCC were diagnosed for a crude overall SCCC incidence rate of 6.8/100,000 person-years. The SCCC incidence rate decreased between 2004 and 2014 with an annual percentage change of -10.9% (95% CI -13.3 to -8.3). PWH residing within latitudes 30°S-34°S had a 49% lower SCCC risk than those residing at < 25°S (adjusted HR 0.67; 95% CI 0.55-0.82). Other risk factors for SCCC were lower CD4 counts and middle-age. There was no evidence for an association of sex or settlement type with SCCC risk. INTERPRETATION An increased risk of developing SCCC was associated with lower CD4 counts and residence closer to the equator, indicative of higher ultraviolet exposure. Clinicians and PWH should be educated on known SCCC preventive measures such as maintaining high CD4 counts and protection from ultraviolet radiation through sunglasses and sunhats when outdoors.