Non-Hodgkin's lymphoma in HIV+ and HIV− men and women in the San Francisco Bay Area: Risk factors by histologic type.

Abstract

101 Background Few risk factors have been identified for non-Hodgkin's lymphoma (NHL) by histologic type in HIV+ or HIV− men and women. Histologic type was examined in a case-control study of these subjects in the San Francisco Bay Area. Methods In-person interviews with questions related to lifestyle and medical history were completed by more than 4000 population-based subjects who were HIV+ and HIV− homosexual and heterosexual men and women with NHL, each with their respective control group. Blood was drawn to determine HIV and HTLV status, CD4, CD8, CD20, and WBC values. Pathology materials were reviewed and were classified according to the Working Formulation. Results Over all histologic categories when comparing homosexual groups, HIV infection was associated with a 20-fold increased risk for NHL (CI=14-31). The most common type of NHL among HIV+ homosexual men was large-cell lymphoma (80%), followed by the Burkitt's group (19%). In contrast, large cell NHL occurred in 52% of HIV− homosexual men, 58% of heterosexual men and 59% of women. HIV− homosexual and heterosexual men and women all had similar proportions by histologic category except for the Burkitt's group. Unexpected was the 11% of HIV− homosexual men with NHL who were categorized with Burkitt's, while <3% of HIV− heterosexual men and 1% of HIV− women were in this group. Reduced risks for NHL associated with allergies to plants were similar for HIV− homosexual men (OR=.56 CI=.16-2.0) and for heterosexual men (OR=.53 CI=.36-.78) and women (OR=.53 CI=.35-.78). Allergies to plants also conveyed reduced risk for Burkitt's but ORs were variable across patient groups (OR=.18 CI=.05-.64 for HIV+ homosexual men to OR=.76 CI=.09-6.5 for women). Increased risk for Burkitt's was observed among HIV− homosexual men who ever had genital warts (OR=2.4), genital herpes (OR=5.6) or syphilis (OR=4.3) although all associations could have been due to chance. No similar increased risks for Burkitt's were observed among HIV+ homosexual men. Among HIV+ homosexual men rimming was associated with similar reduced risks for large cell (OR=.62 CI=.37-1.1) and Burkitt's (OR=.61 CI=.28-1.2) whereas among HIV− homosexual men the risk was decreased for large cell (OR=.29 CI=.11-.79) but elevated for Burkitt's (OR=1.9 CI=.19-18). Decreased risks associated with increased number of sexual partners for HIV+ (<200 vs. ≥200 partners) or HIV− (<40 vs. ≥40 partners) homosexual men were no longer observed by subtype but remained decreased among heterosexual men and women for both NHL subtypes. Conclusion These results provide continued support for the role of allergic reactions in B-cell differentiation and indicate that risk factors may differ by NHL subtype. The increased risk for Burkitt's associated with STDs may be related to lifestyle factors not measured or to an associated viral or bacterial infection. As the number of subjects by subgroups often was small, data need to be pooled across studies to obtain adequate sample size to define associations between risk factors and NHL subtypes. These data may provide insight into an antigen driven process early in lymphomagenesis.