Air pollution and lung cancer link revealed

The reason why air pollution is linked to lung cancer has been revealed for the first time, a conference has heard – resulting in calls for action to reduce dangerous particulates.

A study, presented by Professor Charles Swanton, of the Francis Crick Institute and Cancer Research UK Chief Clinician, London, UK, to delegates at the ESMO Congress 2022 in Paris, France, provides valuable insight into the link between climate change and human health, he said.

The human and laboratory studies showed that exposure to increasing concentrations of airborne particulate matter (PM) 2.5 micrometres (?m) in diameter – PM2.5 – was linked to increased risk of non-small cell lung cancer (NSCLC) with mutations in the EGFR gene, which are present in about half of people with lung cancer who have never smoked.

In laboratory mouse models, PM2.5 particulates were seen to directly cause lung cancer by acting through lung tissue inflammation. This drives the release of interleukin-1?, which causes epithelial cells to transdifferentiate into cancer stem-like cells.

In the presence of mutations in EGFR and in the KRAS gene, these cells can develop into a tumour.

Prof Swanton, study author and ESMO 2022 scientific co-chair, said: “These mutations can be found in over half of normal lung tissue biopsies and are a natural process of ageing. They are necessary, but not sufficient to drive cancer: it is in combination with pollution that the cancer stem cells can expand and initiate a tumour.

“This begins to explain how environmental carcinogens that don’t induce DNA mutations can drive cancer.

“We have to achieve a 50% reduction in greenhouse gas emissions by 2030, and by doing so we will naturally reduce levels of PM2.5. We can all play a part here: we need to cycle more, walk more. It’s worth bearing in mind that PM2.5 cause eight million deaths a year, not just due to cancer but also to other diseases like cardiovascular disease, strokes, dementia – that is more than the deaths caused by tobacco globally.”

He also suggested that targeting interleukin-1? should be further explored as a potential new approach to cancer prevention.

The findings come with a rise in the global incidence of respiratory cancers, with annual new cases expected to jump by about 70% over the next two decades.

As up to half of all cancers are thought to be preventable, prevention is considered by the World Health Organisation (WHO) to be the most cost-effective, and most sustainable, long-term strategy for cancer control.

ESMO director of public policy Dr Rosa Giuliani said: “The ESMO Vision 2025 made very clear that if we want to succeed in tackling cancer, we need to develop a clear plan for primary and secondary prevention, continue to offer the optimal care for cancers that cannot be prevented and adequately support cancer survivorship. Focusing on only one of these areas and neglecting the others would lead to failure.”

The Cancer Prevention across Europe Campaign (PrEvCan) was also launched at ESMO.

Led by European Oncology Nursing Society (EONS) with ESMO as key partner alongside other international organisations, the 12-month campaign will promote and explain the scientific evidence for each one of the 12 recommendations of the European Code Against Cancer (ECAC) to prevent the disease.

It starts next month (October), with smoking as one of the most important cancer risk factors.

Dr Lena Sharp, EONS executive board member and PrEvCan project leader, said: “What is new here is that it is the cancer care workforce leading the way.

“We are the ones who meet patients and their families, so we could intervene on a daily basis supporting and advising people to adopt healthier lifestyles to reduce the risk of new cancers but also to reduce negative effects on the current disease.”

The campaign will target the general public, including the most vulnerable groups who can be difficult to reach, with health promotion and lifestyle advice.

Professor Solange Peters, ESMO president, added: “We thought for a while that prevention should be in the hands of family doctors, but then we started to learn that preventing the disease must be at least partly in the hands of the specialists of a specific disease, in order to convince people about its importance.

“Particularly after COVID, a certain degree of suspicion can happen in medicine. You need to make sure that everything you propose has a basis – and one of these bases for cancer prevention is the burden of cancer, what it represents not only in terms of lost years of life but also in terms of the sustainability of our societies and healthcare systems.”

Prof Peters said oncologists should view prevention as an integral part of oncology care.

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