Increasing incidence of non-Hodgkin's lymphoma in Karachi, 1995-2002

This first population-based study of non- Hodgkin lymphoma (NHL) from any region in Pakistan, provides an overview of the incidence pattern and time trends in Karachi and generates hypotheses for future experimental research. Epidemiological data for 429 incident (1(st) Jan 1995 to 31(st) Dec 2002), microscopically verified nodal and extra-nodal NHL cases, registered at the Karachi Cancer Registry (KCR) for Karachi South, were reviewed. The age standardized incidence rate (ASIR) was 5.3/100,000 in males (M) and 4.1/100,000 in females (F), in 1995. A gradual increase in the annual incidence was observed during the study period, with NHL incidence rate increasing in 2002 to 8.4/100,000 in men and 6.5/100,000 in women, almost double the 1995 rates. NHL affected all age groups in both genders and for each group the ASIR was higher among men than women, with an overall gender ratio of 1.9. The mean ages of the patients were 41.5 years (95% CI 39.1; 43.8) in males and 44.0 years (95% CI 40.8; 47.1) in females. The adult to childhood ratios were 8.6 (M) and 10.7 (F). B-cell NHL comprised 81.0% of NHL in males and 87.3% in females. One fourth of the NHL cases were extra-nodal, the largest group was of gastrointestinal origin (54.1% M, 38.5% F). The gastric component was 21% M and 25.6% F. Odds Ratios for sex, age-groups, ethnicity, religion, and subdivision by socio-economic categories were calculated by considering all malignancies, except lymphoproliferative disorders as controls. The odds ratio (OR) in men was 2.2 (95% CI 0.6; 3.0). Children and adolescents were at the highest risk of developing NHL, especially the 5-9 year olds, in both genders. A marginally higher risk was observed for the lower socioeconomic categories and for ethnicities belonging to Northern and North Western Pakistan (Punjabi, Pushtu and Baluch) residing in Karachi South. The incidence rates of NHL registered in Karachi South are likely to be a reflection of non-AIDS-associated NHL. Estimated HIV/AIDS incidence was too low during the study period in this population to have an impact on NHL incidence. The preponderance of low and intermediate grade lymphomas, paucity of central nervous system NHL and a higher childhood NHL component support this hypothesis. As yet unpublished reports, however, are raising the alarm on rising HIV positivity. NHL correlation with HIV/AIDS status and studies identifying risk factors of non- HIV/AIDS associated NHL (childhood viral infections, Hepatitis C virus, and Helicobacter pylori) are potential areas for future experimental and epidemiological research.