Incidence of lung malignancy in a tertiary care centre – A one year study

Background: Lung cancer is the most common type of cancer in males and the leading cause of death in both sexes. It accounts for 11.3% of all new cancers in India and also associated with a mortality rate of 13.7%. This desolate mortality necessitates for the early diagnosis of lung cancer. The study was conducted to evaluate incidence, gender and age wise distribution of lung cancer and its association with smoking. Methodology: This study was done in the department of pulmonary medicine in Guntur Medical College from September 2016 to august 2017. The study includes 52 patients having clinical and radiological suspicion of lung cancer. All the cases were subjected to USG guided transthoracic needle aspiration was sent for cytology. Inconclusive and malignant cases were further subjected to histopathological examination for confirmation. Results: Out of the 52 patients suspicious of malignancy, 32 patients were finally diagnosed as malignant, 5 patients had benign/inflammatory lesions, 6 cases had no evidence of malignancy/non-specific inflammation, 8 had no opinion possible. Most common type is adenocarcinoma followed by squamous cell carcinoma with an incidence rate of 71.8% & 15.7% respectively. The highest incidence of lung malignancies is seen in 5 decade in both sexes. Conclusions: There is increase in the incidence of lung malignancies in females, throwing light on the causes other than smoking like biomass fuel exposure and second-hand smoking. Adenocarcinoma is the most common type. Further, USG guided transthoracic needle aspiration has a good sensitivity in detecting lung malignancies.


Introduction
Lung cancer is the major oncological problem with increasing incidence and cancer related mortality in the world. It is more common in men in India which accounts for 11.3% of all new cancers and has a mortality rate of 13.7% [1]. In contrast to a decline trend in men in developed countries with a plateau for females, in India, the incidence continues to rise for both males and females [1]. This desolate mortality necessitates for early diagnosis of lung cancer. Cytology has an important role in initial evaluation and diagnosis of lung cancer with less complications. Advances in minimally invasive and radiographically guided sampling procedures have made cytology an important tool in the diagnosis of lung cancer [2]. Usually the minimum size of the lesion required is 20 mm for USG and 15 mm for CT guided needle aspirations, some studies show that under USG guidance, lesions of 10 mm size can be approached safely with solid intervening tissue. Using 18G needle for percutaneous fine needle aspiration is adequate for most lesions, especially for carcinomas [3]. The study was conducted in our institute to evaluate incidence, gender and age wise distribution of lung cancer and its association with smoking.

Materials and Methods
The study was done in the department of pulmonary medicine, Guntur Medical College, Guntur after ethical committee approval and consent of the study subjects. A total of 52 cases were selected from September 2016 to august 2017. All clinically suspected patients of lung carcinoma after routine investigations like chest X-ray, haemogram, urine analysis, microbiological examination of sputum and computed tomography of chest were included. Sputum microscopy positive tuberculosis cases, Bleeding disorder and uraemia were excluded. (As there is a risk of spontaneous bleeding in uraemia and bleeding diathesis which could complicate the procedure of FNAC and biopsy they were excluded from the study, sputum microscopy negative cases with radiological opacities were considered for FNAC as a positive sputum microscopy case was started on antituberculosis treatment under RNTCP). Samples were obtained through USG guided transthoracic fine needle aspiration cytology using 20-gauge needle. Cytological specimens which are inconclusive and suggestive of malignancy were further subjected to histopathological examination using Bard Gun biopsy needle (16-guaze). (In the present study, non-smokers were defined as a person who has smoked less than 100 cigarettes over his/her life time. Rest all are taken as smokers. We recorded his/her smoking habits in terms of, the number of pack years of smoking irrespective of the type of nicotine smoking habit).

Fig. 1: Age and gender distribution
Lung carcinoma incidence is more in females than in males, as observed at our institute, male to female ratio being 0.8:1. The most common age of presentation was in the 5 th decade in both sexes, further it was observed that there is no incidence of cases below 40 years at our institute.

Fig. 2: Gender distribution of malignancy
Most frequent type observed is adenocarcinoma in 23 (71.8%) patients, of which 13 were females and 10 were males, followed by squamous cell carcinoma in 5 (15.7%) patients, of which 2 were females and 3 were males. Finally, metastatic adenocarcinoma was diagnosed in 3 patients (9.3%), small cell neuroendocrine tumour in one case which were confirmed by typing.

Fig. 3: Comparison of smokers and non-smokers with type of lung malignancy
It was observed in the study that almost all the cases diagnosed as squamous cell carcinoma (n=5) were smokers and only 9 out of 23 cases diagnosed as adenocarcinoma were smokers.

Discussion
In the present study a total of 76.9% lung malignancy cases were diagnosed using ultrasound guided procedures. Most common type of carcinoma is adenocarcinoma followed by squamous cell carcinoma, having incidence of about 71.8% & 15.7% respectively. Highest incidence of malignancy is seen in the 5 th decade of life.
Most of the patients in our study had adenocarcinoma (71.8%), similar to most of the Asian and western countries. This shift in trend from squamous cell carcinoma to adenocarcinoma, is attributable partly to the smoking practices and the increase in use of filtered cigarettes. Most of the Indian studies previously have shown squamous cell carcinoma as the common type, but recent studies show, the change in trend from squamous to adenocarcinoma [4].
Tobacco smoking is a well-established risk factor for lung cancer [5]. The number of lung cancer cases reported in our study are slightly on a higher side in females than in males. This increase in trend of lung cancer in females, across the world as well as in India, is due to the biomass fuel exposure and increase in the number of female smokers [1]. To make an impact on mortality resulting from lung cancer in India needs strong public health measures to control tobacco use. Fortunately, this is now being increasingly recognized by the government [6].
The mean age of onset in Mehta M et al study is 5 th decade in males and 6 th decade in females, male to female ratio is 5.1:1, whereas in our study we had a mean age of onset of 5 th decade in both sexes; further the male to female ratio is 0.8:1, suggesting there is more number of female cases diagnosed with lung malignancy at our institute, which had non-resolving pneumonia radiologically. It further alarms us to keep an eye over the increasing trends in the onset of lung malignancies in females and also about the causes of lung cancer other than smoking particularly in countries like India where there is still use of biomass fuel in most of the places.
Most of the cases in India are misdiagnosed as tuberculosis and empirical treatment with anti-tubercular drugs prior to referral to higher centre is one of the important causes for delayed diagnosis of lung cancer in India [1]. The huge burden of TB in India hinders differentiation by the primary care physicians of lung cancer. This can be minimised by high index of suspicion and early diagnosis of lung cancer.

Conclusions
Lung cancer is a common cause of cancer related mortality in India. There is a rise in the number of female cases detected, alarming us for the search of causes like biomass fuel exposure. Simple USG guided transthoracic fine needle aspiration cytology comes handy in early diagnosis of lung cancer; as it needs less technical expertise and usually available in minimal care centres also.