Changing Trend of Lung Cancer Incidence in Northern India

It is well known that smoking is injurious to health which causes lung cancer. Although not all smokers develop lung cancer, fraction of lifelong non-smokers will die from lung cancer. Lung cancer is a major cause of cancer-related death in developed countries with extremely poor overall survival rate. In present study we set out epidemiological pattern with clinical profile of lung cancer patients in north Indian population.


Background
Lung cancer mainly develops by tobacco usage and this is often viewed solely as smoker disease.However, a significant number of patients with lung cancer have no smoking history.Globally approx 1.61 million new cases of lung cancer occur per year, with 1.38 million deaths.This data on cancer patients with lung cancer is a major cause of morality in all over cancer [1].In India, approximately 63,000 new lung cancer cases are reported each year [2].The major risk for developing lung cancer in tobacco use and this disease is often viewed solely as a smoker disease.Although multiple risk factors, including environmental, hormonal, genetic and viral have been implicated in the pathogenesis of lung cancer in never-smokers, no distinct etiological factor has emerged that can explain the relatively high incidence of lung cancer in never smokers and the marked geographic difference in gender proportions.Molecular studies, in particular of the TP53, KRAS, and epidermal growth factor receptor (EGFR), GST genes, demonstrate strikingly different mutation pattern and frequencies in lung cancer patients in non-smoker and smokers [3].In our study, we set to find out clinically meaningful difference between smoker and non smokers, in relation with lung cancer development.

Materials and Methods
It is an observational study, in which we collect data through screening of patients from OPD through diagnosis of lung cancer patients, discussed in the thoracic oncology multidisciplinary meeting at a tertiary care hospital in Lucknow, India, during a 2 year period.The survey was conducted by trained clinical research coordinators under the supervision of physicians using a detailed questionnaire.Patients were interviewed regarding their history of smoking, smoking pattern and use of smokeless tobacco.Following the interview, all patients underwent the routine work-up for lung cancer, including imaging (computed tomography (CT) scan of the thorax and upper abdomen) and pathologic confirmation of the diagnosis.The final therapy plan was noted.Data was entered and analyzed using SPSS software (SPSS for Windows, Version 15).

Results
In the present study 218 patients diagnosed according to histopathology between November 2007 and November 2009.A summary of the patient data is provided in (Table 1).

Risk analysis of carcinogen exposures in association of histopathology with smoking history
Out of 218 patients, Smokers have 63.1 % smokers squamous cell, 20.1% adenocarcinoma, 13.4% mixed type 3.4% small round and in case of non smoker 34.8%, 50.7%, 10.1%, 4.3%.The data of our study show that these are smoker have a more squamous cell and those are non smokers have adenocarcinoma.

Discussion
Relating to measured time in cancer histology are often difficult to study because changes in diagnosis or classification may mimic true changes in disease occurrence [4,5].In a study from Singapore, 32.5% of lung cancer patients have been never-smokers, [6] while in the United States, approximately 10% of lung cancer cases occur in non-smokers [7].
Over the earlier periods distribution of NSCLC pathology has been modified.Squamous-cell carcinoma was the most common histological type of NSCLC, however, since about 1975; there has been a dramatic increase in the incidence of adenocarcinoma, making it the predominant histological subtype of NSCLC [8].Thus far, not much information was available as to the distribution of the histological subtypes in India.Squamous-cell carcinoma was still the predominant histological subtype of NSCLC [9].In our study we found that squamous cell carcinoma accounts for (54.1%) of NSCLC, while only (29.2%) are adenocarcinoma.
Conventionally, Squamous-cell carcinoma of the lung was thought to be smoking-related, rather than adenocarcinoma.The increase in the incidence of adenocarcinoma was thought to be mainly attributable to a change in smoking pattern and an increased preference for filter cigarettes that have low tar, but high nitrate content [10].Earlier studies reported that the increased incidence of adenocarcinoma was confined to smokers [11,12].In contrast, we found a statistically higher occurrence of adenocarcinoma in non-smokers as compared to smokers.This is supported by other studies in the literature [13][14][15][16].Thus, our study and other recent studies suggest that the increase in adenocarcinoma is not solely due to a change in pattern of cigarette smoking, but must be due to non-smokingrelated factors, since the increase is demonstrated in nonsmokers as well.Bidies are more carcinogenic than cigarettes [17], however, it is not known if bidi smoking preferentially causes a particular cancer subtype or if there are any clinical or pathological features that are different in a lung cancer caused by bidi smoking as compared to that caused by regular cigarettesmoking.Among our patients with a history of smoking, the proportion bidi smokers (25.4%) were higher than the socalled "safe" cigarettes (19.4%).Given the wide prevalence of bidi smoking in our country, this may be an important factor to consider while evaluating the Indian epidemiologic profile.Whether there were any significant differences between cancers in bidi smokers compared to that in cigarette smokers is beyond the scope of this study.

Conclusion
In this article we found that squamous cell carcinoma is higher in northern Indian population rather than adenocarcinoma, and it also confirmatory statement that smoker having more squamous cell and nonsmoker having adenocarcinoma in the middle age group.