A case-control study of cancer of the oral tongue and floor of mouth was conducted in Kerala, Southern India, on 228 cases and 453 hospital-based controls, matched for age, sex and religion. We studied pan(bete1)-tobacco-chewing, bidi (local type of cigarette)-and-cigarette-smoking, alcohol-drinking and snuff use, for their associations with risk, in males. Among females, only pan-tobacco-chewing was analyzed, as very few females indulged in the other habits. In males, a significantly increased risk was observed in association with pan-tobacco-chewing, bidi-smoking, bidi-plus-cigarette-smoking (but not cigarette-smoking alone) and alcohol-drinking ( p < 0.001 in all cases), although the effect of alcohol was no longer significant when adjusted for the other significant predisposing factors. Among females, pan-tobacco-chewing had a similar predisposing effect to that observed in males (p < 0.001). In males an adjusted relative risk of 6.14 was associated with chewing 10 or more pan-tobacco quids per day (relative to those who never chewed). The corresponding relative risk in females was 9.27. In males, an adjusted relative risk of 7.46 was observed for those smoking 20 or more bidis per day (relative to never-smokers).
Cancer of the oral cavity is the commonest malignancy among males and the third commonest among females in Southern India (ICMR, 1982(ICMR, -1985;;Krishnan Nair et al., 1988). The annual age-adjusted incidence rates have been reported to be 12.7 per 100,000 males and 12.1 per 100,000 females in Madras, 25 per 100,000 males and 13.1 per 100,000 females in Trivandrum (Sankaranarayanan, 1989).
Only 4 case-control studies on oral cancer have been reported from this region until now (Orr, 1933; Shanta and Krishnamoorthy, 1959, 1963;Hirayama, 1966). These studies have identified pan-tobacco-chewing as a major risk factor for oral cancer. However, smoking and alcohol have not been studied in any detail and many intra-oral sites were studied together in these studies.
Cancer of the oral tongue accounts for 25% of all intra-oral cancers in Southern India and floor of mouth cancer accounts for 5% of cases. The present study addresses these cancers only, since the strength of association with the risk factors may vary among subsites of the oral cavity.