Annual screening for oral cancer detection.

Most oral cancer and oral mucosal screening programs initiated in the past 20 years have been limited to a single examination of the population under study. Age specific, annual oral mucosal screening examination as a part of general health screening has been in operation in Tokonama city, Japan, from 1986. From 1996 the same target population aged 40 years and older has been invited for screening. The program coverage extended to 26% of the city population. During 1995-1998, out of 9536 attendees who participated in a general health and oral mucosal screening program in Tokoname city 6340 subjects (66.5%) re-attended at least for one further screening examination. There was no difference in the attendance for two annual mucosal examinations between male (67.0%) and female (66.2%) subjects. Three thousand nine hundred thirty-five subjects attended oral screening all 3 years (1996-1999) and the overall show-up rate for three consecutive examinations was 61%. During September-October 1996, 42 volunteer dentists carried out 6705 mouth examinations among those aged 40 years and older at the Municipal Center. One oral cancer was detected in 1996, in a subject free of any mucosal disease in the previous year. Among the screen-negative cases in 1996, 78% re-attended for screening in 1997 and 79% re-attended in the subsequent year. In the cohort that re-attended screening (1996-1998), oral mucosal pathology detected in three consecutive screenings included 18 leukoplakias, 24 with oral lichen planus and 343 other benign mucosal lesions. The number of subjects who complied to return and who remained disease-free over the 3-year period amounted to 3860, 59% of the disease-free subjects seen in 1996. A regular smoker was less likely to attend oral cancer screening in the three consecutive years of follow-up (odds ratio: 0.832, 95% CI 0.701-0.988). Satisfactory participation can be obtained for annual oral mucosal screening in Japan: this allows detection of new lesions, including oral cancer and leukoplakia (a surrogate marker of cancer risk). The number of new oral cancers detected in the program was too low to determine the optimal frequency for oral cancer screening but new oral leukoplakias were found on annual re-screening: the data indicate that the interval between two screens for this population should not be greater than 12 months.