Pollution can take years off lung cancer patients' lives

Those battling lung cancer, you should consider moving to the countryside as a recent population-based study has found that air pollution can shorten your survival.

The trends were most noticeable for early stage disease, particularly adenocarcinoma, the most common type of non-small cell lung cancer that accounts for 80 percent of lung cancer cases, the University of Southern California findings showed.

In a bid to clarify air pollution's potential impact on an individual's chances of survival after diagnosis, the researchers tracked the health outcomes up until the end of 2011 of more than 352,000 people newly diagnosed with lung cancer between 1988 and 2009, and whose details had been entered into the US California Cancer Registry.

Their average age at diagnosis was 69. Nearly 53 percent of the cancers were diagnosed at an advanced stage (distant spread); and the average survival time for localised (early stage) disease was 3.6 years, falling to 1.3 years for regional spread, and just 4 months for distant spread.

For patients with early stage disease, average survival time was shortest for those with small and large cell cancers (around 1.5 years) and longest for those with adenocarcinoma (around 5 years).

Participants' average exposure to nitrogen dioxide (NO2), ozone (O3), particulate matter of less than 10 um, and less than 2.5 um, in diameter (PM10 and PM2.5 ) was calculated using data from US Environmental Protection Agency air quality monitoring stations, mapped to area of residence.

This is an observational study so no firm conclusions can be drawn about cause and effect. And the researchers point to several caveats, including a lack of data on potentially important risk factors, such as an individual's lifestyle, smoking status, and alcohol intake; and the inability to capture road traffic pollution.

Nevertheless, there are plausible biological mechanisms for the associations found, they said, as ambient air pollution has been classified as a cancer causing agent by the International Agency for Research on Cancer (IARC).

They concluded: "Our observed associations were clinically significant ([less than or equal to 38 percent] increased risk of death depending on stage and pollutant), suggesting that reductions in exposure have the potential to improve lung cancer survival."

The study is published online in the journal Thorax.