Nasopharyngeal carcinoma (NPC) has a unique and complex etiology that is not completely understood. Although NPC is rare in most populations, it is a leading form of cancer in a few well-defined populations, including natives of southern China, Southeast Asia, the Arctic, and the Middle East/North Africa. The distinctive racial/ethnic and geographic distribution of NPC worldwide suggests that both environmental factors and genetic traits contribute to its development. This review aims to summarize the current knowledge regarding the epidemiology of NPC and to propose new avenues of research that could help illuminate the causes and ultimately the prevention of this remarkable disease. Well-established risk factors for NPC include elevated antibody titers against the Epstein-Barr virus, consumption of salt-preserved fish, a family history of NPC, and certain human leukocyte antigen class I genotypes. Consumption of other preserved foods, tobacco smoking, and a history of chronic respiratory tract conditions may be associated with elevated NPC risk, whereas consumption of fresh fruits and vegetables and other human leukocyte antigen genotypes may be associated with decreased risk. Evidence for a causal role of various inhalants, herbal medicines, and occupational exposures is inconsistent. Other than dietary modification, no concrete preventive measures for NPC exist. Given the unresolved gaps in understanding of NPC, there is a clear need for large-scale, populationbased molecular epidemiologic studies to elucidate how environmental, viral, and genetic factors interact in both the development and the prevention of this disease. PurposeIntriguing hallmarks of nasopharyngeal carcinoma (NPC) include its striking racial/ethnic and geographic variation, as well as its multifactorial etiology involving the interplay of environmental, viral, and genetic risk factors. The precise roles of these factors in the development of NPC, however, remain unknown. The purpose of this review is to highlight what is understood about the epidemiology of NPC, as well as to present unresolved research questions that call for large-scale molecular epidemiologic studies of NPC to illuminate the underlying causes of this fascinating disease. Review MethodsA thorough review of the literature related to the etiology of NPC was undertaken, starting with a Medline search from 1966 onward. Additional papers, book sections, and monographs were identified through examination of reference lists. Because this review aims to present the epidemiologic evidence in a range of topic areas, rather than to calculate overall estimates of effect, formal quantitative methods were not used. All relevant papers have been cited to provide a comprehensive summary of the evidence. Inclusion or exclusion criteria were not applied to individual reports, but the strength, consistency, and relevance of the findings were considered in weighing the evidence.Descriptive Epidemiology

Purpose-Lung cancer is a leading cause of cancer death worldwide. While smoking remains the predominant cause of lung cancer, lung cancer in never-smokers is an increasingly prominent public health issue. Data on this topic, particularly lung cancer incidence rates in never-smokers, however, are limited.Methods-We review the existing literature on lung cancer incidence and mortality rates among never-smokers and present new data regarding rates in never-smokers from large, population-based cohorts: 1) Nurses' Health Study, 2) Health Professionals Follow-up Study, 3) California Teachers Study, 4) Multiethnic Cohort Study, 5) Swedish Lung Cancer Register in the Uppsala/Örebro region, and the 6) First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study.Results-Truncated age-adjusted incidence rates of lung cancer among never-smokers aged 40 to 79 years in these six cohorts ranged from 14.4 to 20.8 per 100,000 person-years in women and 4.8 to 13.7 per 100,000 person-years in men, supporting earlier observations that women are more likely than men to have non-smoking-associated lung cancer. The distinct biology of lung cancer in neversmokers is apparent in differential responses to epidermal growth factor receptor inhibitors and an increased prevalence of adenocarcinoma histology in never-smokers.

Our results confirm the associations between certain autoimmune disorders and risk of NHL and suggest that the associations may not be general but rather mediated through specific NHL subtypes. These NHL subtypes develop during postantigen exposure stages of lymphocyte differentiation, consistent with a role of antigenic drive in autoimmunity-related lymphomagenesis.