Role of tobacco in the development of head and neck squamous cell carcinoma in an eastern Indian population.

The head and neck squamous cell carcinoma (HNSCC) accounts for about 30-40% of all cancer types in India and the subcontinent in general. HNSCCs are primarily not hereditary, but rather a disease of older and middle aged adults. Many etiological factors like tobacco, alcohol and HPV infection are known to play important roles. Eastern India, particularly Kolkata, has a population heavily exposed to various types of smoked and smokeless tobacco, with only limited exposure to alcoholic beverages. Since there have been no previous epidemiological studies on tobacco as the main risk factor for head and neck carcinogenesis in Kolkata, we here carried out a hospital based case control study in the city and its adjoin regions. Data from 110 patients diagnosed with HNSCC and a similar number of matched control samples were analyzed using the chi-square test. Survival status of the patients was also analyzed using the Kaplan-Meier method. A tobacco habit was significantly correlated with the incidence of HNSCC and persons with current addiction had a 2.17 fold increased risk of cancer development. Dose-response relationships were seen for the frequency (p=0.01) and duration (p=0.02) of tobacco exposure with the risk. No significant difference in impact was found with smoked as opposed to smokeless tobacco in the development of the disease. Among HNSCC patients, significant poor survival in cases with tobacco habit than in those with no addiction and in cases with >10 years of addiction than in those with 10 years of addiction. Our data suggest that tobacco in both smoked and smokeless forms is the most important risk factor for both development and prognosis of HNSCCs and may be a major source of field cancerization on the head and neck epithelium in the eastern Indian population.