A prospective ascertainment of cancer incidence in sub-Saharan Africa: The case of Kaposi sarcoma

Abstract

In resource-limited areas, such as sub-Saharan Africa, problems in accurate cancer case ascertainment and enumeration of the at-risk population make it difficult to estimate cancer incidence. We took advantage of a large well-enumerated healthcare system to estimate the incidence of Kaposi sarcoma (KS), a cancer which has become prominent in the HIV era and whose incidence may be changing with the rollout of antiretroviral therapy (ART). To achieve this, we evaluated HIV-infected adults receiving care between 2007 and 2012 at any of three medical centers in Kenya and Uganda that participate in the East Africa International Epidemiologic Databases to Evaluate AIDS (IeDEA) Consortium. Through IeDEA, clinicians received training in KS recognition and biopsy equipment. We found that the overall prevalence of KS among 102,945 HIV-infected adults upon clinic enrollment was 1.4%; it declined over time at the largest site. Among 140,552 patients followed for 319,632 person-years, the age-standardized incidence rate was 334/100,000 person-years (95% CI: 314-354/100,000 person-years). Incidence decreased over time and was lower in women, persons on ART, and those with higher CD4 counts. The incidence rate among patients on ART with a CD4 count >350 cells/mm(3) was 32/100,000 person-years (95% CI: 14-70/100,000 person-years). Despite reductions over time coincident with the expansion of ART, KS incidence among HIV-infected adults in East Africa equals or exceeds the most common cancers in resource-replete settings. In resource-limited settings, strategic efforts to improve cancer diagnosis in combination with already well-enumerated at-risk denominators can make healthcare systems attractive platforms for estimating cancer incidence.

Keywords: Africa; HIV/AIDS; Kaposi sarcoma; antiretroviral therapy; incidence.

Figure 1

Summary of the process of patient selection for the study of Kaposi sarcoma (KS) prevalence and incidence in the three healthcare systems in East Africa. ART denotes antiretroviral therapy.

Figure 2

Frequency of accompanying skin biopsy at the time of diagnosis of Kaposi sarcoma (KS) among HIV‐infected patients over time at three healthcare systems in East Africa. Panel A shows instances of prevalent KS diagnosis, and panel B shows cases of incident KS. Line represents locally weighted scatterplot smoothing (LOWESS). Q represents quarter of the calendar year.

Figure 3

Prevalence of Kaposi sarcoma at the time of clinic enrollment among HIV‐infected patients over time at three healthcare systems in East Africa. Line represents locally weighted scatterplot smoothing (LOWESS). AMPATH denotes Academic Model Providing Access to Healthcare in western Kenya; ISS denotes Immune Suppression Syndrome Clinic in Mbarara, Uganda; and IDI denotes Infectious Diseases Institute in Kampala, Uganda. Q represents quarter of the calendar year.

Figure 4

Incidence rate of Kaposi sarcoma (per 100,000 person‐years) over time among HIV‐infected patients at three healthcare systems in East Africa. Line represents locally weighted scatterplot smoothing (LOWESS). AMPATH denotes Academic Model Providing Access to Healthcare in western Kenya; ISS denotes Immune Suppression Syndrome Clinic in Mbarara, Uganda; and IDI denotes Infectious Diseases Institute in Kampala, Uganda. Q represents quarter of the calendar year.