From 1,567 contacted subjects with provisional diagnoses of NHL, 1,094 were eligible and 966 agreed to participate (88.3%). From these participants, 486 were confirmed as NHL at the time of the statistical analysis. A total of 1,022 control subjects were recruited; the participation rate in the controls was 76.9%.
shows the frequency of each NHL subtype. The majority were of diffuse large cell type (54.9%), of which 146 (30.0%) were confirmed to be of B cell lineage by immunohistochemistry (IHC). Other common subtypes were chronic lymphocytic leukemia (11.9%), follicular lymphoma (6.3%), and mantle cell lymphoma (3.3%). We combined the T cell lymphoma subgroups—precursor T cell, peripheral T cell, and not otherwise specified T cell—into one group, T cell lymphoma (n = 23, 6.6%). We also combined mucosa associated lymphoid tissue lymphoma with nodal marginal zone lymphoma into one group (n = 24, 6.6%) according to the World Health Organization classification system. The remaining subgroups had very few cases to be included in statistical analysis. The unclassified lymphoma subgroup and the cutaneous lymphoma not otherwise specified subgroup was excluded from further analysis.
Prevalence of NHL subtypes among the NHL patients, Egypt 1999–2004
shows the distributions of age, sex, marital status, and rural birthplace for the largest NHL subgroups. Cases with mantle cell lymphoma, chronic lymphocytic leukemia, or diffuse large B cell lymphoma had mean ages that were similar to those of controls (within five years). T cell lymphoma cases were notable for having a mean age nearly 15 years younger than controls (35.5 vs. 50.3 years, respectively). Cases and controls did not differ by percentage of males, except for the T cell lymphoma group, which had the lowest proportion of males (37.5% vs. 66.4% in controls, p = 0.012). This case group, along with mantle cell lymphoma, also differed from controls in marital status. Higher proportions of cases with rural birthplace compared to controls were characteristic of diffuse large B cell and chronic lymphocytic leukemia.
Social and demographic characteristics of major NHL subtypes, Egypt 1999–2004
The prevalence of viral hepatitis markers among the NHL subtypes is described in . Both anti-HCV and HCV-RNA measures are dichotomous variables. Statistically significant associations with past and current HCV infections were observed for diffuse large B cell (OR = 2.6, 95% CI 1.8–3.9, and OR = 3.2, 95% CI 2.1–4.7, respectively) and marginal zone lymphomas (OR = 3.4, 95% CI 1.4–8.5, and OR = 4.4, 95% CI 1.8–10.6, respectively). All models were adjusted for sex, age, and birthplace. In addition, current HCV infection was associated with a significantly elevated risk of follicular lymphoma (OR = 3.3, 95% CI 1.3–8.0). Among all the analyzed subtypes, there was no group for which only anti-HCV and not HCV RNA positivity was associated with NHL risk. For all cases combined, the OR was 1.9 (95% CI 1.4–2.6) and 2.4 (95% CI 1.8–3.2) for past and current HCV infections, respectively. Odds ratios for blood transfusion were as follows: diffused B = 0.6 (0.3–1.0), leukemia = 1.4 (0.7–2.7), T-cell = 0.3 (0.1–1.5), Mucosa-Associated Lymphatic Tissue Lymphomas = 1.9 (0.8–4.8), follicular = 0.2 (0.02–1.4), and Mantle = 2.0 (0.7–5.9). Since no association between NHL subtype and blood transfusion was significant, we did not include these results in the paper.
Prevalence and odds ratios of serum anti-HCV in major NHL subtypes, Egypt 1999–2004
When the polytomous analysis was performed to analyze the heterogeneity by NHL subtypes, the odds ratios for HCV infection remained elevated for diffused large B cell (OR = 2.0 95% CI 1.4–2.9 for anti HCV, and OR = 2.6, 95% CI 1.8–3.7 for HCV RNA). The marginal zone lymphoma odds ratios for anti HCV stayed elevated as well at 2.3 (95% CI 1.1–5.4), but HCV RNA became insignificant (OR = 3.2 95% CI 0.2–2.6). The results for follicular lymphoma were no longer significant in the polytomous regression (OR = 0.8 95% CI 0.3–2.2 for anti HCV).
We also examined the possible associations between the major NHL subgroups and behavioral, occupational, environmental, and medical characteristics where the exposed group consisted of at least 10 subjects. Smoking, treatment of shistosomiasis, diabetes, exposures to pesticides, or other chemicals were not significantly associated with any case subtypes nor were any of these odds ratios >1.5. Shoveling grains, which was included in the questionnaire as a possible marker of aflatoxin exposure, was associated with elevated risk of follicular lymphoma (OR = 2.2, 95% CI 1.2–4.3). Even after adjustment for sex, age, and urban vs rural birthplace, positive association with growing rice was seen for diffuse large B cell lymphoma (OR = 5.1, 95% CI 2.3–11.2). Dog ownership was associated with increased risk for mantle cell lymphoma (OR = 7.5, 95% CI 1.7–32.4, p-value 0.0069), while cat owners had increased risk of chronic lymphocytic leukemia (OR = 3.5, 95% CI 1.1–11.3).