Smoking cessation before lung cancer diagnosis linked to longer survival
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People who quit smoking prior to a lung cancer diagnosis demonstrated considerably reduced risk for death due to all causes compared with those who continued to smoke, according to study results scheduled for presentation during the ASCO20 Virtual Scientific Program.
Researchers observed this benefit across all patient subsets regardless of sex, disease stage or histology.
“This result may seem obvious, but even if a person quits smoking within 2 years of lung cancer diagnosis, he or she will have a survival benefit,” Aline Fusco Fares, MD, clinical research fellow at Princess Margaret Cancer Centre, said during a press conference. “If a smoker is participating in a lung cancer screening program, this information could help convince that person to quit, and that is a very important message from our study.”
Lung cancer is the leading cause of cancer mortality, accounting for approximately 25% of cancer deaths. Smoking causes an estimated 80% of lung cancer deaths, according to study background.
Extensive prior research has demonstrated the impact of tobacco smoking on lung cancer risk; however, the extent to which smoking cessation prior to lung cancer diagnosis affects all-cause and malignancy-specific survival had not been established.
Fares and colleagues used the International Lung Cancer Consortium database — which aggregates lung cancer cohort and case-control studies — to determine if smoking cessation before lung cancer diagnosis appeared associated with longer OS and lung cancer-specific survival and — if so — whether those associations were affected by time since smoking cessation.
Researchers analyzed data from 17 studies that included 34,649 patients with lung cancer. An equal percentage were current smokers (41%; n = 14,322) and former smokers (41%; n = 14,273) at diagnosis, whereas 18% (n = 6,054) were never-smokers.
Results showed never-smokers (adjusted HR [aHR] = 0.76; 95% CI, 0.73-0.8) and former smokers (aHR = 0.88; 95% CI, 0.86-0.91) achieved longer OS than current smokers.
Former smokers achieved longer OS than current smokers regardless of whether they quit smoking more than 5 years before lung cancer diagnosis (aHR = 0.8; 95% CI, 0.76-0.84), 2 to 5 years before diagnosis (aHR = 0.83; 95% CI, 0.77-0.9) or less than 2 years before diagnosis (aHR = 0.88; 95% CI, 0.82-0.94).
Fares and colleagues conducted sensitivity analysis on 13 of the 17 included studies to evaluate the association between time since smoking cessation and lung cancer-specific survival.
Results showed those who quit smoking more than 5 years before lung cancer diagnosis achieved significantly longer lung cancer-specific survival (aHR = 0.85; 95% CI, 0.78-0.92). The associations were not statitiscally significant among those who quit less than 2 years before diagnosis (aHR = 0.95; 95% CI, 0.86-1.05) or 2 to 5 years before diagnosis (aHR = 0.93; 95% CI, 0.83-1.04).
“Although we can’t say that all these deaths after a lung cancer diagnosis are specifically due to the disease, a proportion of them certainly are,” researcher Geoffrey Liu, MD, MSc, clinician scientist at Princess Margaret Cancer Centre, said in a press release.
The U.S. Preventive Services Task Force recommends adults aged 55 to 80 years with a 30 pack-year smoking history who either continue to smoke or quit within the previous 15 years undergo annual lung cancer screening with low-dose CT.
Because lung cancer screening can serve as a teachable moment regarding the benefits of smoking cessation, Fares and colleagues conducted an additional analysis to mimic the target lung cancer screening population.
Among individuals with more than a 30 pack-year smoking history, Fares and colleagues reported “strikingly strong” OS results for those who had quit smoking less than 2 years prior to diagnosis (aHR = 0.86; 95% CI, 0.8-0.93), 2 to 5 years before diagnosis (aHR = 0.83; 95% CI, 0.76-0.9) and more than 5 years before diagnosis (aHR = 0.78; 95% CI, 0.74-0.83) compared with current smokers.
Among individuals who had less than a 30 pack-year history, the OS benefit did not reach statistical significance for those who quit less than 2 years before diagnosis (aHR = 0.95; 95% CI, 0.92-1.02) or 2 to 5 years prior to diagnosis (aHR = 0.86; 95% CI, 0.74-1.01) compared with current smokers. However, the OS benefit did reach significance for those who quit more than 5 years before diagnosis (aHR = 0.77; 95% CI, 0.72-0.82).
“We saw a slightly bigger benefit to quitting among people who had smoked heavily for over 30 years compared with the overall population of former smokers. For long-term smokers, the benefits of quitting cannot be overstated,” Liu said.
The researchers intend to collaborate with local lung cancer screening programs, using their findings to develop a pilot program of smoking cessation counseling sessions. – by Mark Leiser
Reference:
Fares AF, et al. Abstract 1512. Scheduled for presentation at: ASCO20 Virtual Scientific Program; May 29-31, 2020.
Disclosures:
Liu reports honoraria from, consultant/advisory roles with, speakers bureau roles with or research funding from AbbVie, AstraZeneca/MedImmune, Bayer, Bristol-Myers Squibb, Merck, Novartis, Pfizer, Roche, Roche Canada and Takeda. Fares and the other researchers report no relevant financial disclosures.
Perspective
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Michael B. Steinberg, MD, MPH, FACP
The study by Fares and colleagues demonstrated that stopping smoking prior to a lung cancer diagnosis reduced all-cause mortality compared with continuing to smoke. This benefit was observed not only among those who stopped smoking earlier — more than 5 years prior to lung cancer diagnosis — but also among those who smoked within 2 years of their cancer diagnosis.
These results reinforce the critical fact that it is never too late to stop smoking. We know that the improvements to health from smoking cessation begin within minutes of quitting (reduced carbon monoxide and lower blood pressure), continue for weeks to months (improved lung function and reduced pulmonary infections) and last for years (lower risk for heart attack, stroke and cancer). Many of the patients we see have smoked from adolescence through several decades. We often hear, “I’ve smoked for so long, why stop now? The damage is already done.” As it turns out, that is not the case.
We have known that continuing to smoke after a cancer diagnosis imparts significant harms, including worse surgical, radiation and chemotherapeutic outcomes, higher rates of recurrent cancer and additional primary malignancies, and worsening symptoms, including chronic pain. Now, we can add that quitting smoking before a lung cancer diagnosis — even for only a short time (less than 2 years), can reduce mortality. Additionally, for those patients who have smoked and have not yet been diagnosed with lung cancer, they should be strongly encouraged to receive lung cancer screening with low-dose CT if they meet eligibility criteria. This critical early detection tool — shown to reduce both lung cancer and overall mortality — is recommended by the U.S. Preventive Services Task Force.
Whether it is preventing cancer, detecting it in its earliest stages or reducing mortality associated with cancer, we clinicians need to continue to drive home the message to all of our patients: The right time to quit smoking is now, regardless of how long you have smoked.
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Fares AF, et al. Abstract 1512. Scheduled for presentation at: ASCO20 Virtual Scientific Program; May 29-31, 2020.
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