For people who are diagnosed with early−stage lung cancer, quitting smoking after the diagnosis doubles their odds of surviving the next five years. The study does not appear to be applicable to patients with late−stage cancers.

The research team, led by Amanda Parsons the Center for Tobacco Control Studies at the University of Birmingham College of Medicine and Dentistry in the UK, looked at data from 10 earlier studies. "We used meta−analysis to summarize their findings," says Parsons. "Quitting smoking was associated with around double the chance of surviving at any time point compared to people who continued to smoke."

For people who continued smoking after lung cancer diagnosis, their odds of surviving the next five years were only 29−33%. But for people who quit smoking after the diagnosis, their chances of being alive in five years rose to 63−70%.

For people who continued smoking after lung cancer diagnosis, their odds of surviving the next five years were only 29−33%. But for people who quit smoking after the diagnosis, their chances of being alive in five years rose to 63−70%. All patients had undergone chemotherapy, radiation, or surgery to treat the cancer.

The researchers says that the results are likely due to a decreased risk of the cancer reoccurring, rather than other factors like improvements in heart or lung function.

While the results are encouraging, the researchers point out that they may only hold true for patients with an early diagnosis, as the research studies did not include participants who suffered from later−stage hung cancer. Parsons says that “the results can only be applied to this group of lung cancer patients. This work does not tell us anything about the benefits of quitting smoking if you have advanced disease."

While it seems intuitive that hospitals would offer assistance to people to quit smoking after they’ve been diagnosed with lung cancer, Parsons says that such programs are, unfortunately, not routine, though a few facilities may do so.

The new study is published in the January 21, 2010 online edition of the journal BMJ.