Incidence and geographic distribution of endemic Burkitt lymphoma in northern Uganda revisited

Abstract

Endemic Burkitt lymphoma (BL) is etiologically associated with Epstein-Barr virus and ecologically linked to Plasmodium falciparum malaria. However, these infections imperfectly correlate with BL epidemiology. To obtain recent epidemiological data, we studied district- and county-specific BL incidence and standardized incidence ratios using data collected from 1997 to 2006 at Lacor Hospital in northern Uganda, where studies were last done more than 30 years ago. Among 500 patients, median age was 6 years (interquartile range 5-8) and male-to-female ratio was 1.8:1. Among those known, most presented with abdominal (56%, M:F 1.4:1) vs. only facial tumors (35%, M:F 3.0:1). Abdominal tumors occurred in older (mean age: 7.0 vs. 6.0 years; p < 0.001) and more frequently in female children (68% vs. 50%; OR 2.2, 95% CI 1.5-3.5). The age-standardized incidence was 2.4 per 100,000, being 0.6 in 1-4 year olds, 4.1 in 5-9 year olds and 2.8 in 10-14 year olds and varied 3- to 4-fold across districts. The incidence was lower in districts that were far from Lacor and higher in districts that were close to Lacor. Although districts close to Lacor were also more urbanized, the incidence was higher in the nearby perirural areas. We highlight high-BL incidence and geographic variation in neighboring districts in northern Uganda. Although distance from Lacor clearly influenced the patterns, the incidence was lower in municipal than in surrounding rural areas. Jaw tumors were characterized by young age and male gender, but presentation has shifted away from facial to mostly abdominal.

Figure 1

Map showing location of study area in northern Uganda and the names and district boundaries (centre map). Study maps show, on the lower panels the crude BL incidence and, on the upper panels, the standardized incidence ratio, by county for the periods 1997-2001(left) and 2002-2006 (right). Bold lines indicate district boundaries, thin lines indicate county boundaries. Hatch marked area indicates counties without any case counts.

Figure 2

A: Line graph showing the percent of cases presenting as abdominal (with or without jaw) or only jaw tumors by calendar year and percent of cases by calendar year (1997-2006) B: Line graph showing the percent of children with only jaw, abdominal (with or without jaw) and the percent of cases BL by age (0 through 14 years). C: Bar graphs showing age-standardized (to the world population) incidence rates for BL for 10 districts in northern Uganda for calendar-year periods 1997-2001 and 2002-2006.