A review of Indian literature for association of smokeless tobacco with malignant and premalignant diseases of head and neck region.

In India, about 60% of tobacco users use smokeless tobacco (ST) alone. Head and neck squamous cell carcinoma is one of the most common cancers in India. International Agency for Research on Cancer (IARC) monograph (Vol 89) found a significant association between ST use and oral cancer. However, only a few articles from India were included in this monograph. To overcome this lacuna, we have reviewed the articles published from India investigating the association between ST use and malignant and premalignant diseases of head and neck region. Data collection has been performed by computer-aided search of the MedLine and PubMed databases using different combinations of the key words. For malignant lesions, only cohort and case control studies were considered for review. For premalignant lesions and dental diseases other than case control studies, some cross-sectional studies have also been reviewed. Studies found a significant association between ST use and cancer of the oral cavity. The association was stronger for the buccal mucosa compared to tongue and for females compared to males. Significant association noted between cancer of the hypopharynx and oropharynx with ST use but no definitive association noted for cancer of the larynx and nasopharynx. Some dental disease and oral premalignant conditions were also associated with ST use. Indian studies suggest ST use is strongly associated with cancer of the oral cavity, oropharynx and hypopharynx.