An Effect-evaluation Study Of The Screening For Nasopharyngeal Cancer

Among the common malignant tumors, nasopharyngeal carcinoma (NPC) is well known for its typical epidemiological characteristics. In most populations of the world, NPC is a rare disease and the incidence rates are below 1 case per 100,000 person-years. In contrast, however, NPC is a common malignant tumor and the incidence rates are as high as 15 cases person-years in the countries of Southeast Asia and in Southern China, especially in Guangdong province.Three factors are thought to play an important role in the etiology of NPC: Genetics, diet and Epstein-Barr virus (EBV). However, the custom of taking salted fish at early age has changed with the development of economy and the upgrade of living condition. There is so for insufficient evidence to recommend preventive strategies based on vaccination for EBV. The congenital factors could not currently be removed by the modern technique. Therefore, there is no a feasible primary prevention for NPC. The hope of prevention for NPC is now relied on the secondary preventive strategies, mainly on the screening of NPC.In order to qualify for being considered for a screening program, a disease needs to fulfill several criteria:1) the disease has serious consequences; 2) early treatment is more effective than treatment started at a later date; 3) the prevalence of the detectable pre-clinical phase (DPCP) is high enough among the people screened. First point is easy to fulfill. NPC is responsible for considerable mortality in the high risk population. The second point is supported by the results from the clinical studies. Although the five year survival rates of cases with an advanced NPC kept lower than 20 percent in past 20 years, the figures for the NPC cases in an early stage raised to higher than 80 percent. Third point needs to demonstrate. It is reported in a study that the antibodies of VCA/IgA appeared 20 months before the diagnosis of NPC. More than 60 percent of NPC cases detected by serological screening in Guangxi and in Guangdong were in the early stage (stage I and II). Therefore, NPC seems a...