Non-Hodgkin Lymphoma in the Middle East Is Characterized by Low Incidence Rates With Advancing Age

In the Middle East, incidence rate ratios (IRRs) of non-Hodgkin lymphoma (NHL) to Hodgkin lymphoma (HL) are more than 50% lower than the United States.

Age-specific incidence rates (ASIRs), age-adjusted incidence rates (AAIRs), and IRRs of NHL:HL were compared using the cancer registries of Iraq, Jordan, Saudi Arabia, and US SEER.

The NHL AAIR (95% CI) per 100,000 population was 4.4 (4.1 to 4.7) for Iraq, 5.4 (4.6 to 6.2) for Jordan, 4.7 (4.4 to 5.1) for Saudi Arabia, and 13.2 (13.0 to 13.4) for the United States. The HL AAIR was 1.8 (1.6 to 2.0) for Iraq, 1.8 (1.4 to 2.2) for Jordan, 2.1 (1.9 to 2.2) for Saudi Arabia, and 2.3 (2.2 to 2.4) for the United States, with respective NHL:HL IRR of 2.4 (2.2 to 2.7), 3.0 (2.4 to 3.8), 2.2 (2.0 to 2.5), and 5.7 (5.5 to 6.0). NHL ASIRs for the Middle East and the United States were similar until 30 to 39 years of age. Thereafter, ASIR of NHL peaked at 20 to 33 per 100,000 at age 70 years in the Middle East regions, all much lower than the US age 70 years rate of greater than 100 per 100,000. Diffuse large B-cell lymphoma (DLBCL) represented 52% of NHL in Sulaimaniyah Province of Iraq and 51% of NHL in Saudi Arabia. Both regions had AAIR for DLBCL less than 42% of DLBCL in US SEER. Pediatric Epstein-Barr virus-related Burkitt's lymphoma at 8% was the second most frequent NHL in Sulaimaniyah but made little contribution to overall NHL rates.

The incidence of HL was slightly lower than in the United States, but it was the markedly lower rates of adult NHL with advancing age, including the predominant DLBCL, that accounted for the low NHL:HL IRR in these Middle Eastern countries.