Comparison of carcinogenicity of betel quid with and without tobacco: an epidemiological review.

A comparison of carcinogenicity of the habit of chewing betel quid with and without tobacco has been attempted through a reassessment of the available epidemiological evidence on aetiology of oral cancer and pre-cancer. Primary evidence comes from the reports which emphasize a low incidence of oral cancer among population groups who practise the habit of chewing betel quid without tobacco compared with those which practise the habit of chewing betel quid with tobacco. A more specific comparison is sought here through the quantitative estimation of the relative risks of the two types of betel habits. Out of three studies selected, two studies showed that the relative risk for the habit of betel quid without tobacco was not significant whereas the relative risk for the habit of betel quid with tobacco was highly significant. In the third study, although both relative risks were significant, the relative risk for the habit of betel quid with tobacco was significantly higher than the risk for the habit of betel quid without tobacco. The evidence from studies of oral pre-cancer was also in the same direction. It is suggested that in intervention and primary prevention programmes for oral cancer, the emphasis in the first instance might be upon the exclusion of tobacco from the betel quid rather than the complete discontinuation of the habit of chewing betel quid.