Changing epidemiology and risk factors for gastrointestinal non-Hodgkin's lymphoma in a north American population: Population-based study

OBJECTIVES: To assess the incidence, risk factors, and endoscopic presentation of gastrointestinal non-Hodgkin's lymphoma (GI NHL) in a large predominantly urban adult population sample. METHODS: A comprehensive database review of all diagnoses of GI NHL in the Calgary Health Region over a 5-yr period (1999-2003) was undertaken. Longer-term data from a population-based HIV database (1985-2004) were also reviewed. A regional pathology database was used to corroborate case identification. All patients 18 yr of age or older were included. Age- and gender-adjusted incidence rates were calculated. Within the HIV-positive population, incidence rates were compared over time. Endoscopic appearances were assessed and compared. RESULTS: Fifty-six GI NHL cases occurred during the study period. The age- and gender-adjusted annual incidence of GI NHL was 1.73 per 100,000 in the study population. The majority were diffuse large B-cell histology (54%), followed by lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) (29%). Increasing age, history of kidney transplant, and H. pylori positivity in MALT lymphoma were identified as risk factors. Within the HIV-positive population, a highly significant drop in GI NHL was seen over time, with an incidence of 3.86 per 1,000 patient-years in 1985-1989 compared to zero cases in 2000-2004, despite a greater prevalence of HIV disease (P < 0.0001 for trend). MALT lymphoma was less likely to manifest as a mass on endoscopy versus other presentations (P < 0.05). CONCLUSIONS: Population-based GI NHL incidence rates in Calgary are higher than those described elsewhere in North America or in Britain. The incidence of GI NHL within the HIV population has virtually disappeared, presumably due to the advent of highly active retroviral therapy.