It's never too late to stop smoking, even for smokers already diagnosed with lung cancer, a new analysis shows.
A systematic review of published trials of smokers diagnosed with early stage lung cancer disclosed that patients who stopped smoking when diagnosed were about twice as likely to survive for five years as those who continued to smoke after diagnosis, wrote Amanda Parsons, a research fellow at the University of Birmingham in England, and colleagues in a paper published online Jan. 22 by the British Medical Journal.
Continuing smoking was associated with a significantly increased risk of early death from all causes, as well as an increased risk of cancer recurrence, they wrote.
The authors extrapolated the benefit of quitting smoking from both the recurrence and ealy death data. What they found through their research is that an estimated 33 percent of smokers diagnosed with an early form of lung cancer at age 65 would survive for five years if they continued to smoke, versus an estimated 70 percent among those who quit smoking after diagnosis.
"This review has found evidence that after lung cancer has been diagnosed, reductions in risk of developing a second primary or recurrence were associated with quitting within seven years, suggesting that, even at this stage the prognostic outlook can be improved by smoking cessation," the researchers wrote.
Whether this observation can be explained by nicotine or by other components of tobacco smoke is unknown, but regardless of the exact mechanism of harm, the authors wrote, the findings "support the hypothesis that continued smoking affects the behavior of a lung tumor."
In an accompanying editorial, Dr. Tom Treasure, a cardiothoracic surgeon at University College London, and psychiatrist Janet Treasure, also from University College, wrote that the new review demonstrated that the impact of continued smoking is so large that both patients and "those caring for them should be given this information because the potential benefit is great."
But there is one significant problem both for patients and doctors, the editorialists noted: "Fewer than one in three patients with lung cancer survive even one year, so the patients likely to benefit are probably healthier to begin with. So, although the information is valuable, its application may be limited."
The researchers noted that more study may be needed to further clarify the findings due to a number of reasons -- not the least of which is the fact that those patients who got the worst news from their doctors about the progression of their disease were usually more likely to quite, but also more likely to die earlier. For this reason, the researchers said, the review could underestimate the benefits of quitting for the average lung cancer patient.