Why are East Asians more susceptible to several infection-associated cancers (carcinomas of the nasopharynx, stomach, liver, adenocarcinoma of the lung, nasal NK/T-cell lymphomas)?

There are at least five cancers with uniquely high incidence amongst East and Southeast Asian ethnic groups - namely nasopharyngeal carcinoma (NPC); gastric carcinoma; hepatocellular carcinoma (HCC); adeno-carcinoma of the lung in female non-smokers and nasal NK/T-cell lymphomas. They all appear to be related to an infective cause (Epstein Barr Virus, Helicobacter pylori, hepatitis B virus). We hypothesize that a genetic bottleneck 30,000years ago at the Last Glacial Maximum could have resulted in unique genetic polymorphisms in Toll-like receptor 8, making East Asians more vulnerable to these infective associated cancers. This bottleneck could have been caused by the presence of malaria in the southern Himalayan conduit between central and East Asia; and only those with an attenuated innate immune response to the malarial parasite (perhaps reflected by the TLR8 polymorphism) were spared the ravages of cerebral malaria; allowing these people to cross into east Asia, but then rendering them susceptible to later endemic infections and their associated cancers.

Nasopharyngeal carcinoma in young patients.

Nasopharyngeal carcinoma (NPC) is rare in under 20-year-olds. Early diagnosis greatly improves survival. A retrospective review of 12 young NPC patients (seven males, five females, mean age 16 years) was performed to identify differing patient and tumour characteristics from adult NPC. Seventy-five per cent presented with neck lumps and 25% with headache. None had a family history of NPC or epistaxis. One patient had early stage NPC, and 11 had late stage NPC. Three late stage patients who received chemoradiotherapy had better clinical outcomes than six late stage patients receiving only radiotherapy. There were six deaths, five bony recurrences and one postnasal space recurrence. The 11 late stage patients' five-year actuarial survival was only 29%. Headache is an important symptom for young NPC. Late stage presentation and distant recurrences are also more common, supporting an increased role of chemotherapy.