JCO November 10, 2014 vol. 32 no. 32 3593-3595 © 2014 by American Society of Clinical Oncology Smoking Cessation After Cancer Freddy Sitas, Marianne F. Weber, Sam Egger, Sarsha Yap, May Chiew, Dianne O'Connell

1. JOURNAL OF CLINICAL ONCOLOGY COMMENTS AND CONTROVERSIES
Smoking Cessation After Cancer
Freddy Sitas, Cancer Council New South Wales, Wooloomooloo; University of Sydney, Camperdown; and University of New
South Wales, Kensington, New South Wales, Australia
Marianne F. Weber, Cancer Council New South Wales, Wooloomooloo; and University of Sydney, Camperdown, New South
Wales, Australia
Sam Egger, Sarsha Yap, and May Chiew, Cancer Council New South Wales, Wooloomooloo, New South Wales, Australia
Dianne O’Connell, Cancer Council New South Wales, Wooloomooloo; University of Sydney, Camperdown; University of New
South Wales, Kensington; and University of Newcastle, Callaghan, New South Wales, Australia
The benefits of smoking cessation after a cancer diagnosis are
overlooked. In many high-income countries, cancer survival has im-proved
significantly over the last few decades.1 About half of patients
with cancer are now expected to survive their cancer for at least 10
years after diagnosis.2 This trend is likely to improve with the advent of
better therapies. Data on cancer survival in low-income countries are
sparse and too variable to summarize succinctly.3 However, many
people with cancer still continue to smoke despite smoking being a
known and often reversible cause of premature death as a result of
cancer, cardiovascular, respiratory, and several other diseases.4 In ad-dition,
continued smoking after a cancer diagnosis increases the risk of
second primary tumors and cancer recurrence and is a cause of treat-ment
complications.5 Smoking cessation after a diagnosis imparts
significant survival benefits for people with cardiovascular disease,
diabetes, and multiple sclerosis.6 By comparison, the evidence regard-ing
the benefits of smoking cessation after a cancer diagnosis is limited,
as has been detailed in a recent policy statement from the American
Association for Cancer Research.7 Specifically, the deleterious effects
of continued smoking on overall survival after a cancer diagnosis have
been quantified to a certain degree, and the relative risk of death has
varied depending on the cancer type, stage of disease, and length of
follow-up. That is, all-cause mortality among cancer survivors who
continue to smoke after a diagnosis is significantly worse than those
who have never smoked.8-18
However, the evidence regarding the benefits of smoking cessa-tion
after a cancer diagnosis on prognosis and/or mortality is limited,
especially for cancers for which smoking is not identified as a primary
risk factor. One recent study of all cancers diagnosed at a single treat-ment
center in the United States found that the overall mortality rate
was 20% higher among continuing smokers compared with recent
quitters (ie, those who stopped smoking within 1 year before diagno-sis).
19 A meta-analysis of 10 studies regarding patients with lung can-cer
found that those who quit smoking at the time of diagnosis had a
5-year survival rate of 63% and 70% for small-cell and non–small-cell
lung cancer, respectively, versus 29% and 33% among those who
continued to smoke.14Twostudies of headandneck cancer found that
the risk of mortality among patients who quit smoking around the
time of diagnosis was significantly less than the risk for those who
continued to smoke (relative risk, 0.6).16,20 Several studies have also
reported improved disease-free survival among recent quitters with
lung cancer21,22 headandneck cancers,20,23,24 andbladder cancer.25 By
contrast, at least one study has reported no benefit of quitting at
diagnosis of lung cancer.26
There is a need to further quantify the potential benefits of quit-ting
smoking by comparing mortality in people who stop smoking
after a cancer diagnosis compared with those who continue to
smoke.27-29 Although large randomized or observational studies
would be ideal to measure the effect of quitting, these would have to be
large; for smoking cessation compliance rates of 5% and 40%, one
would need to randomly assign approximately 600,000 and 9,500
patients with cancer, respectively. Observational studies are also a
possibility, but researchers need to account for methodologic issues
such as confounding by indication and other prognostic factors. A
recent report by Warren et al19 on the mortality of a heterogeneous
group of patients who quit smoking after a cancer diagnosis now
provides some empirical data across several cancer types. To supple-ment
this evidence, we estimated the effects of smoking on the prob-abilities
of survival after a cancer diagnosis from two westernized
populations (ie, cancer registry survival datafrom 2001 to 2008 inNew
South Wales, Australia, and the Surveillance, Epidemiology, and End
Results [SEER] Program in the United States30).Weassumed that the
all-cause mortality risk for patients with cancer who were smoking at
diagnosis was 1.17, 1.29, and 1.38 times that of recent quitters, former
smokers, and never-smokers, respectively (ie, these were the relative
risks estimated by Warren et al,19 in which patients reporting that they
had stopped smoking more than 1 year before diagnosis were defined
as former smokers, current smokers were those still smoking at diag-nosis,
and recent quitters were those who quit within 1 year before
diagnosis). We also assumed that never-smokers, recent quitters, for-mer
smokers, and current smokers represented 58.3%, 3.0%, 37.8%,
and 5.4% of the Australian patients with cancer at diagnosis, respec-tively
(estimated from an Australian cancer case-control study of
approximately 8,000 people31), and 37.2%, 10.1%, 35.0%, and 17.6%
of US patients with cancer at diagnosis, respectively (as reported by
Warren et al). Under these assumptions, the gap between survival
probabilities for continuing versus never-smokers at 8 years after
diagnosis is large (ie, 37% and 43% for Australian and US continuing
smokers, respectively, v 49% and 54% for Australian and US never-smokers,
respectively); survival in recent quitters is also substantially
greater than that for continuing smokers at 43% and 49% for
VOLUME 32 NUMBER 32 NOVEMBER 10 2014
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2. Sitas et al
A B
probability)
0.8
(Survival 0.6
Year 0.5
8-breast cancer. Int J Clin Pract 59:1051-1054, 2005 Australian and US patients, respectively (Fig 1). Interestingly, sur-vival
is better for all US compared with all Australian patients with
cancer, despite the fact that a considerably higher proportion of US
patients had been smokers at one time or another (63% v 45%). If
smoking prevalences had been similar between the two countries,
the superiority of survival for US patients with cancer might have
been more profound.
There are numerous potential limitations to these estimates, in-cluding
possibly different case mixes between the two countries, esti-mates
of smoking prevalences that might not be typical of the target
populations, and the potential for local variations in the treatment of
people with cancer who continue to smoke. Furthermore, the relative
risks reported by Warren et al and used in our calculations may not be
generalizable to other populations with different distributions of un-derlying
cancers, stages of cancer, and cancer therapies. It should also
be noted that observational studies could be used to improve the
model inputs, such as the proportion of recent quitters and nonquit-ters
at diagnosis, which would improve the accuracy and precision of
the survival estimates. Despite the limitations, these survival estimates
provide some preliminary information to guide future policy and
research, and they suggest that significant improvements in US and
Australian cancer survival may be achieved by complementing cancer
treatment with strong adjuvant smoking cessation programs. Similar
programs might also provide substantial improvements in cancer
survival in other regions of the world such as Canada and some Asian
and European countries, in which significant numbers of patients
continue to smoke after their diagnosis.32-35 There are also substantial
gains to be made, especially in Asian countries where an even greater
number of patients with cancer smoke after diagnosis (eg, 65% of
patients with cancer continued smoking after diagnosis in the Shang-hai
Cohort Study35). Although large studies are needed to provide
robust estimates of the effect of smoking cessation on cancer survival,
the existing literature and our estimates suggest that it would be
prudent to implement smoking cessation in treatment guidelines as an
essential part of cancer care. Smoking cessation is likely to impart
significant benefits to patients with cancer, but most physicians do not
actively provide antismoking guidance.36-38 In Australia, guidelines
for the management of cancers that are not considered to be related to
0.8
0.6
0.5
smoking often do not specify recommendations for smoking cessa-tion.
For example, in the national clinical practice guidelines for the
management of breast cancer, there are recommendations for in-creased
physical activity, reduced alcohol intake, improvements in
diet, and body weight management, but not smoking cessation.39-42
Although the focus of clinical guidelines such as these is to prevent
cancer recurrence, smoking cessation advice has the shared purpose of
increasing survival overall. After all, for a smoker with any cancer,
being alive is a necessary precondition for acting on recommendations
around lifestyle modification.
AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST
The author(s) indicated no potential conflicts of interest.
AUTHOR CONTRIBUTIONS
Manuscript writing: All authors
Final approval of manuscript: All authors
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DOI: 10.1200/JCO.2014.55.9666; published online ahead of print at
www.jco.org on September 29, 2014
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