Association between extranodal natural killer/T-cell lymphoma and hepatitis B viral infection: a case-control study.

Extranodal natural killer/T-cell lymphoma, nasal type (ENKTL) is a rare subtype of lymphoma that is often associated with poor clinical prognosis. Several studies have shown that hepatitis B virus (HBV) infection may be associated with increased risk of B-cell non-Hodgkin lymphoma; however, because of the rarity of ENKTL, little is known about its association with HBV. Our study aimed to assess whether HBV infection was associated with increased odds of ENKTL. We conducted a hospital-based case-control study including 417 ENKTL cases and 488 age- and sex-matched subjects with nonmalignant diseases unrelated to HBV infection. Multivariable unconditional logistic regression analyses were performed to estimate adjusted odds ratios [AOR] and their corresponding 95% confidence intervals (CI). The results of the multivariable analysis showed that after adjustment for a set of known risk factors, patients previously infected with HBV (HBsAg-seronegative/anti-HBc-seropositive) and naturally immune to HBV (anti-HBs-seropositive/anti-HBc-seropositive) were at significantly greater odds of being diagnosed with ENKTL (AOR, 1.497; 95% CI 1.098-2.042, P=0.033 and AOR, 1.871; 95% CI 1.302-2.689, P=0.001, respectively). After adjusting for other factors, significantly greater odds of being diagnosed with ENKTL were observed among cases who reported ever drinking alcohol (AOR, 1.675; 95% CI 1.054-2.660, P=0.029). The odds of ENKTL diagnosis were not significantly associated with ABO blood type, cigarette smoking status or family history of cancer. The results of our study suggest that patients previously infected with HBV and naturally immune to HBV were at greater odds of being diagnosed with ENKTL.