Nasopharyngeal carcinoma in Brunei Darussalam: low incidence among the Chinese and an evaluation of antibodies to Epstein-Barr virus antigens as biomarkers

Hsien YC, Abdullah MS, Telesinghe PU, Ramasamy R
Correspondence: Prof Ranjan Ramasamy, ramasamy@im.ubd.edu.bn

ABSTRACT
Introduction Little or no information is available on the prevalence of nasopharyngeal carcinoma (NPC) among different ethnic groups in Brunei, or how useful plasma IgA antibodies are against viral capsid antigen (VCA) and early antigen (EA) in the diagnosis of NPC, even though they are routinely measured in patients suspected to have NPC.
Methods The National Cancer Registry at Raja Isteri Pengiran Anak Saleha (RIPAS) Hospital was used to identify NPC patients diagnosed between 2000 and 2006. Clinical data and antibody test results for 38 NPC patients and for nine patients suspected of NPC but later diagnosed as negative for NPC by biopsy (control group) were obtained from the Oncology and Histopathology Departments at RIPAS Hospital.
Results The annual incidence rates for NPC among the major ethnic groups in Brunei were determined and compared to data from Singapore and Peninsular Malaysia. The most significant finding was that the average annual incidence of NPC among Bruneian Chinese males (4.1 per 100,000 persons) was significantly lower than that for Chinese males from Singapore (15.9) and Peninsular Malaysia (19.6). IgA anti-VCA and IgA anti-EA were sensitive and specific to NPC in Brunei in accordance with studies elsewhere. The measurement of IgA antibodies against VCA by ELISA was the better serological test for NPC. However, many stage IV NPC cases did not possess IgA anti-VCA and IgA anti-EA.
Conclusion Determining the factors that are responsible for a lower incidence of NPC among Chinese males in Brunei Darussalam may be useful for formulating measures to reduce NPC incidence elsewhere. The possible tendency for the loss of IgA antibodies against VCA and EA in advanced stages of NPC needs to be established with a larger number of patients, and the causes elucidated, in order to better understand the disease process in NPC.

Keywords: cancer biomarkers, cancer epidemiology, Epstein-Barr virus antigens, IgA antibodies, nasopharyngeal carcinoma
Singapore Med J 2009; 50(4): 371-377