Smoking cessation at any point before a lung cancer diagnosis—even within two years—leads to an improvement in overall survival, researchers reported at a media briefing ahead of the 2020 American Society of Clinical Oncology (ASCO) Annual Meeting.

“This research shows that if you’re a smoker and you quit, no matter when you quit, you will be more likely to survive after being diagnosed with lung cancer, compared to someone who continues smoking,” said lead investigator Aline Fusco Fares, MD, of Princess Margaret Cancer Centre in Toronto. 

Due to the COVID-19 crisis, this year’s meeting will be held as a virtual scientific program to be presented May 29 to 31 via ASCO’s website (asco.org). ASCO indicated that more than 2,200 abstracts were accepted for virtual presentation and an additional 3,400 were accepted for online publication. Most of these abstracts are now available in the ASCO Meeting Library.

It is well known that tobacco smoking is a strong risk factor for lung cancer, and quitting lowers the risk. But so far there has been limited research on how the timing of smoking cessation affects overall and lung cancer-specific survival. In particular, little is known about the benefits of quitting after a lifetime of smoking. 

“After a lifetime of smoking, patients often feel it is too late to quit smoking and that the damage has already been done,” Fares said at the media briefing. Lung cancer screening, which is recommended for current or former heavy smokers—those who smoked the equivalent of at least a pack a day for 30 years—could offer a “teachable moment” to encourage smoking cessation, she suggested.

The researchers looked at data from more than 35,000 patients in the International Lung Cancer Consortium (ILCCO) cohort. The analysis included 17 ILCCO studies done in North America, Europe and Asia that had available information on when people quit smoking.

Among the approximately 35,400 lung cancer patients in these studies, nearly half were current smokers at the time of diagnosis, about 30% were former smokers and about 20% had never smoked.

As expected, never smokers and former smokers had better overall survival compared with current smokers.

Among the former smokers, those who had quit more than five years before diagnosis showed a 20% improvement in overall survival, and those who had quit two to five years prior had a 16% improvement. But even those who had quit within two years had a 12% survival benefit compared to those who continued to smoke. The survival benefits were found to be somewhat greater for heavy smokers (22%, 17% and 14%, respectively).

Looking at lung cancer-specific survival (that is, a reduction in death due to lung cancer only), those who had quite five or more years ago showed a 15% improvement, Fares reported. There was a trend toward improvement for those who had quit two to five years ago or less than two years ago, but for these groups the benefit was smaller and did not reach the threshold for statistical significance, meaning it could have been due to chance.

“The take home messages are very clear,” Fares said. “Quitters showed higher survival rates among lung cancer patients, including those quitting within two years of diagnosis. Smokers can benefit from quitting even shortly before lung cancer diagnosis, therefore the study [results] can be summarized to patients as ’it’s never to late to quit smoking.’”

Commenting on the findings, ASCO president Howard Burris III, MD, added in a press release, “We’ve been encouraging people to quit smoking for a long time. These results add more weight to this public health message and provide additional incentive for smokers—particularly those who have smoked for many years—to quit.”

Click here to read the ASCO study abstract.

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