Australians who quit smoking after a cancer diagnosis could live years longer, new modelling shows, gaining precious time and boosting their quality of life.
Those who quit smoking could live from a median of several months to more than two years longer than those who keep smoking, depending on their type of cancer and its severity, the research published in Cancer Epidemiologyon Wednesday shows.
“The earlier you stop smoking, the more beneficial it is, but it can still make a difference after a cancer diagnosis,” said senior author Associate Professor Freddy Sitas, from UNSW’s International Centre for Future Health Systems, who led an international team of researchers.
“Those given a higher chance of survival when diagnosed with cancer have the most to gain by quitting smoking,” he said.
For cancers with a better prognosis, like prostate and breast cancer, 92% of people would survive at least five years after diagnosis if they quit smoking, up from 82%, equivalent to a median gain of 2.1 years.
For cancers with a poorer prognosis, like lung and brain cancer, for which the odds of surviving at least five years would rise from 18.3% to 20.4%, delivering a median gain of three months.
The overall five-year survival rate of cancers analysed in the study, would lift from 63.9% to 71.5%, or an 11-month increase.
“It’s never too late to quit,” said first author, UNSW Dr Nina El-Haddad. “Some people might question if it's worth it after a cancer diagnosis, but it does matter.
“Smoking impacts the effectiveness of the treatment people receive, the risk of their cancer reoccurring and their risk of getting a secondary cancer as well. If you quit, you have a better chance of survival, so it’s crucial.”
Modelling the benefits of quitting smoking
With little detailed data available on the impact of quitting smoking after a cancer diagnosis, researchers turned to a long-running study of more than 30,000 cancer patients in Japan, which ran from 1985 to 2009 and tracked smoking history.
The study had the largest cohort of cancer patients of all types – out of 23 analysed studies – providing a unique perspective of survival benefits in relation to smoking cessation. Subjects were identified from a hospital-based cancer registry, which has collected information on cancer diagnosis, clinical stage, and lifestyle factors including smoking history.
The researchers – from Australia, Japan and South Korea – then used the finding to model the benefits of quitting smoking on Australian cancer survival scenarios, looking at the impacts on cancers with five-year survival rates ranging from 10-90%.
A/Prof. Sitas said improvements in cancer survival rates since then meant the estimated benefits of quitting smoking post cancer diagnosis were likely on the conservative side. As survival rates continue to rise, so will the benefits of quitting smoking post diagnosis.
He also stressed that quitting smoking was not an alternative to medical care, noting the estimates were calculated on top of existing survival rates which were based on the successes of ongoing medical treatment.
“The benefits from quitting smoking are on par with some other medical interventions, but only in addition to existing treatments. It is not a case of trading one for the other,” said A/Prof. Sitas.
Reducing toxic side effects during cancer treatment
In addition to giving people with cancer more time, quitting smoking can improve their quality of life and reduce toxicity from radiotherapy.
“Smoking during cancer treatment causes significant side effects so it is important for oncology staff to take smoking seriously and encourage their patients to quit,” A/Prof. Sitas said.
“The minute you stop smoking, your response to radiotherapy is better, your response to chemotherapy is better. There are less toxic side effects,” he said. “The last thing you want to do while you're being treated is smoke.”
However, he acknowledged that quitting smoking would be of little priority or benefit for some, such as those with late-stage cancer.
“There is so much wrong going on at that time, that a conversation about smoking is probably not a priority, but in the middle ground, anywhere from a survival rate of 10 or 20% to 90% there’s a conversation to be had about the benefits of quitting.”
More focuses needed on smoking cessation in cancer care
The researchers hope the numbers provide a clear guide to cancer patients about the benefits of quitting, but also prompt health practitioners to initiate more conversations on smoking cessation programs and benefits, where appropriate.
“We would like to see smoking cessation better integrated into cancer care,” said Dr El-Haddad. “We want more oncologists to prioritise the discussion that it’s never too late to quit smoking and that there are survival gains to be made by doing so.”
The researchers said better training across the health system, to support smoking cessation, was needed, as was more thorough hospital data collection on the smoking history of patients.
“We also need further studies using more recent data to validate and refine the estimates in the context of today’s cancer care,” A/Prof. Sitas said.
A/Prof. Sitas is Editor-in-Chief of Cancer Epidemiology. The paper was managed and peer reviewed without his involvement.
Contact details:
Kate Burke
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E: kate.burke@unsw.edu.au
