A systematic review of measures of effectiveness in screening for oral cancer and precancer.

Nine databases were searched for studies reporting a range of measures on the effectiveness of screening for oral cancer and precancer in primary care. Of 1114 papers generated in a search of nine databases, full texts of 90 were scrutinised by two reviewers to ensure that they were concerned with oral cancer/precancer, reported an oral cancer screening programme/exercise and included at least one effectiveness outcome. Criteria for considering studies for the review covered types of studies, participants, interventions and outcome measures. The latter included measures of both end point and interim outcome and also process. Of 90 full text articles screened, examiners agreed on the inclusion of 28 (initial agreement -- kappa=0.60). The remaining 62 were excluded and the reasons recorded. The studies included showed substantial heterogeneity regarding objectives and study design, location and setting, numbers and characteristics of participants, screening personnel, methods of recruitment and types of data collected. Only one study, from the Indian sub-continent, reported a randomised controlled trial: interim results showed 14.9% of intervention subjects died after 3 years compared with 56.3% of non-intervention controls. The review overall produced no evidence in favour of or against the potential benefits associated with an oral cancer screening programme. It was concluded that there are insufficient available data to make an unequivocal determination as to the effectiveness of oral cancer screening programmes at the present time. However, a recent further report on the Indian study published after completion of the review, provides some evidence that screening for oral cancer may be effective, at least in developing countries with a high incidence of the disease.