Evolving epidemiology of lung cancer in India: Reducing non-small cell lung cancer-not otherwise specified and quantifying tobacco smoke exposure are the key.

BACKGROUND: Adenocarcinoma is the most prevalent histological type of lung cancer (LC) in developed countries while squamous cell carcinoma (SqCC) has so far been the most common type at our center. Herein, we report our continued assessment of the epidemiological trend of LC aimed at determining any change in the histological distribution.

METHODS: Retrospective analysis involving all consecutive newly diagnosed LC patients over a 4-year period (March 2011-February 2015). Demographic characteristics, histology, and staging data for current data set were compared with our previously published data (2008-2011). As before, smoking index (SI) was used to group patients as never (SI = 0), light (SI = 1-100), moderate (SI = 101-300), and heavy (SI ≥301) smokers.

RESULTS: Majority of 1301 patients had advanced disease (Stages IIIB = 30.1%; IV = 53.3%), were males (82.3%) and current/ex-smokers (76.9%). Adenocarcinoma and SqCC (36.4% each) were equally prevalent. As compared to our previous study, adenocarcinoma increased (36.4% vs. 27.5%) and nonsmall cell lung cancer-not otherwise specified (NSCLC-NOS) decreased (5.1% vs. 10.9%) significantly (P < 0.001). The current study had more heavy smokers (68.3% vs. 61.1%; P = 0.013) and median SI was also higher (500 vs. 400; P = 0.001). Among SI-based groups, significant differences were observed for age, gender, body mass index, histology, TNM stage, and metastatic disease distribution.

CONCLUSION: Reduction in NSCLC-NOS has led to adenocarcinoma and SqCC being equally prevalent at our center in North India despite an increase in heavy smokers. Accurate histological NSCLC subtyping is necessary for optimal epidemiological assessment.