Role of tobacco smoking, chewing and alcohol drinking in the risk of oral cancer in Trivandrum, India: A nested case-control design using incident cancer cases

Summary

Oral cancer is one of the most common cancers in the world, with two-thirds of the cases occurring in developing countries. While cohort and nested case-control study designs offer various methodological strengths, the role of tobacco and alcohol consumption in the etiology of oral cancer has been assessed mainly in case-control studies. The role of tobacco chewing, smoking and alcohol drinking patterns on the risk of cancer of the oral cavity was evaluated using a nested case-control design on data from a randomized control trial conducted between 1996 and 2004 in Trivandrum, India. Data from 282 incident oral cancer cases and 1410 matched controls were analyzed using multivariate conditional logistic regression models. Tobacco chewing was the strongest risk factor associated with oral cancer. The adjusted odds ratios (ORs) for chewers were 3.1 (95% confidence interval (CI) = 2.1–4.6) for men and 11.0 (95%CI = 5.8–20.7) for women. Effects of chewing pan with or without tobacco on oral cancer risk were elevated for both sexes. Bidi smoking increased the risk of oral cancer in men (OR = 1.9, 95%CI = 1.1–3.2). Dose-response relations were observed for the frequency and duration of chewing and alcohol drinking, as well as in duration of bidi smoking. Given the relatively poor survival rates of oral cancer patients, cessation of tobacco and moderation of alcohol use remain the key elements in oral cancer prevention and control.

Introduction

Oral cancer is one of the most common cancers in the world, with approximately 274 300 new cases and 127 500 deaths occurring each year.¹ Two-thirds of those cases occur in developing countries and the majority are over the age of 40 years at the time of diagnosis. The highest incidence rates have been observed in the Indian sub-continent.¹ Five-year relative survival for oral cancer patients is approximately 30% in selected regions of India.² The poor overall survival reflects the advanced stage at diagnosis for the vast majority of these patients.

Findings from case-control studies have suggested chewing tobacco, smoking and alcohol drinking as risk factors for oral cancer and its precancerous lesions.3, 4, 5, 6, 7, 8, 9, 10, 11 However, case-control studies have methodological weaknesses that limit the interpretation of findings such as selection bias and exposure misclassification. The role of tobacco and alcohol consumption in the etiology of oral cancer has rarely been assessed using cohort or nested case-control designs. These two designs avoid or minimize most of the limitations of case-control designs. The aim of our study was to evaluate the role of tobacco chewing, smoking and alcohol drinking patterns on the risk of cancer of the oral cavity, using a nested case-control design on data from a randomized control trial carried out between 1996 and 2004 in Trivandrum, southern India.