New Delhi: Lung cancer is commonly associated with tobacco smoking, but it is increasingly being diagnosed among non-smokers in India, especially the youth, women and people with low immunity.

“Out of every 10 patients diagnosed with lung cancer, around three patients have no history of smoking,” Dr Ujjwal Parakh, senior consultant for respiratory medicine at New Delhi’s Sir Ganga Ram Hospital, told ThePrint.

Dr Anant Mohan, head of the pulmonology department at the All India Institute of Medical Sciences (AIIMS), put the number at 20 to 25 per cent of lung cancer patients. “The ratio of non-smokers among those suffering from lung cancer is swelling year after year,” he said.

According to Dr Navneet Sood, pulmonology consultant at Dharamshila Narayana Superspeciality Hospital, the incidence of lung-cancer among non-smokers has doubled in the last decade.

“A decade back, we used to find 10 to 15 per cent of patients who suffer from lung cancer but are non-smokers. This has doubled now,” Sood said.

Doctors blame the increasing exposure to outdoor and indoor air pollutants like PM2.5, apart from passive smoking and genetic cancer, for the malaise.

Delhi, which, along with several cities and towns in North India, is in the grip of a health emergency because of air pollution, saw its worst day in three years Sunday 3 November, when its 24-hour average air quality index stood at 494. November is also when the world observes Lung Cancer Awareness Month.

“Smoking tobacco was considered the top reason for developing lung cancer. Earlier, the cases of non-smokers acquiring lung cancer were rare. But today, we are commonly diagnosing these cases every day, mostly in younger individuals, women and people with compromised immunity,” Parakh said.

Mohan added: “There are several reasons which could lead to increasing incidence of lung cancer, and air pollution is one of the most relatable reasons, considering the changes in the environment.”

Dr G.C. Khilnani, former head of AIIMS’ pulmonary medicine and sleep disorders department, who is now chairman of the PSRI Institute of Pulmonary, Critical Care and Sleep Medicine, agreed. “It has been well-established that lung cancer has become equally prevalent in non-smokers. Blame the ever-growing air pollution apart from other lifestyle factors,” he said.

An ‘epidemic’ in India

According to a report released by the Indian Council of Medical Research (ICMR), lung cancer is turning into an epidemic in India at an alarming rate. It accounts for a higher number of deaths in India than colorectal cancer, prostate cancer and breast cancer.

In any case, it is a high-mortality cancer, which accounts for “14.5 per cent of all cancers in men and 8.4 per cent in women globally”, the report stated.

“It is a leading cause of cancer death in men worldwide at 22 per cent, which means that one in five of all cancer deaths in men occurs due to lung cancer,” it added.

The death rates in lung cancer are high due to difficulties in diagnosis — data shows that only “15 per cent of cases of lung cancer are curable at the time of diagnosis”.

Previous studies

A study conducted by Sir Ganga Ram Hospital in 2018 said the ratio of smokers and non-smokers is around 1:1, i.e. 50 per cent of people don’t smoke.

“A total of 150 cases of lung cancer were studied between March 2012 and June 2018, and 50 per cent patients were found to be non-smokers. Over 21 per cent patients were below the age of 50,” the study stated.

Dr Arvind Kumar, chairman, Centre for Chest Surgery at Sir Ganga Ram Hospital, had told ThePrint at the time: “I am personally shocked by an alarming rise in cases, occurrences in younger individuals, non-smokers and women.

“We have seen patients from most northern states, including UP, Bihar, Uttarakhand, Delhi, Punjab, and Jammu and Kashmir. In Delhi, even a newborn becomes a smoker with her first breath. There is no escape.”

A 2017 study in the Indian Journal of Cancer had also shown that lung cancer is being diagnosed more in non-smokers than smokers. It had suggested there was a need to look beyond smoking and find fresh reasons. “The take-home message for both the clinicians as well as the policymakers is to study factors beyond tobacco exposure to understand the direction of the current lung cancer epidemic,” it stated.

The story is not just restricted to Delhi — a 2012 study by Mumbai’s Tata Memorial Hospital found that 52.1 per cent of lung cancer patients had no history of smoking. The study contrasted this with a Singapore study that put the number of non-smoking lung cancer patients at 32.5 per cent, and another in the US that found the number to be about 10 per cent.

In January 2017, researchers at AIIMS, Bhubaneswar, had published a demographic profile of lung cancer in eastern India, which found that 48 per cent of patients had not been exposed to active or passive smoking; 89 per cent of women patients had never smoked, while the figure for men was 28 per cent.

The ‘pollution’ link

As reported by ThePrint earlier, data and studies from the major cancer treatment centres across the country as well as case-specific evidence from specialists suggest a clear link with air pollution, although there is no nationwide data yet to confirm this increased incidence.

Dr Randeep Guleria, one of India’s top pulmonologists and director of AIIMS, had said there was plenty of data indicating a link between lung cancer and indoor pollution, especially coal and biomass burning, and that similar links could be drawn with the possible impact of outdoor air pollution, although more robust data would help establish the link more clearly.

The nature of lung cancer cases being reported is changing too — more cases of adenocarcinoma are being reported, which is linked with a mutation in genes caused by a range of environmental and other factors. More adenocarcinoma cases are being reported elsewhere in the world too, but not at the same speed as in India.

The International Agency for Research on Cancer (IARC), the specialised cancer agency of the World Health Organization, classified outdoor air pollution as carcinogenic to humans in 2013, citing an increased risk of lung cancer from greater exposure to particulate matter and air pollution.

Since fewer people smoke nowadays thanks to the worldwide anti-smoking sentiment, the increase in the number of lung cancer cases definitely has another reason, Dr M.S. Kanwar, senior consultant for respiratory medicine and pulmonology at Indraprastha Apollo Hospital in Delhi, had said last year.