It is not easy to stop smoking. In fact, in one study examining over 130 scientific articles that included over 50,000 people who were diagnosed with either lung cancer or head and neck cancer, about one-third of people continued to smoke tobacco after their diagnosis. Rates of continued smoking declined in the first few months following a cancer diagnosis – corresponding to when patients were receiving treatment – but then increased again as more time passed.
Quitting, though, is one of the most valuable things you can do to improve your prognosis. Tobacco use following many cancer diagnoses has been shown to increase the risk of developing a second cancer and dying of the initially diagnosed cancer or of other causes. It is also a risk factor for cancer recurrence, poorer response to treatment and higher rates of side effects from treatment.
For example, in studies conducted in people with lung or head and neck cancers, those who quit smoking had an almost 30% improved rate of survival.
The data is comparable for alcohol use. An analysis of 15,000 adults with a cancer diagnosis in the National Institutes of Health All of Us Research Program reported that 78% were current drinkers, 13% exceeded moderate drinking, and 24% participated in binge drinking.
In one study of cancer survivors with alcohol use disorder, those who continued drinking alcohol had higher rates of readmission to the hospital following a cancer diagnosis. Another study that compared drinkers and nondrinkers with upper aerodigestive tract (oral cavity, pharynx, larynx and esophagus) cancer found that those who drank alcohol had over double the risk of developing another cancer.
While it appears that minimising or eliminating alcohol intake after cancer improves outcomes, the evidence is not as robust as for smoking cessation.
Habits to start after a cancer diagnosis: Exercise and diet modifications
Exercise, either during or after cancer treatment, should be considered a form of complementary medicine that can improve fatigue, quality of life, muscle strength, body weight and body composition. Higher levels of physical fitness are also associated with improved survival in people with cancer. For people undergoing treatment with chemotherapy or radiation therapy, we advise them that every little bit of exercise helps, but to rest or dial back when their bodies tell them to.
A large analysis of 150 studies found that women with breast cancer who exercised had a 36% reduction in overall mortality (because of cancer or other causes, such as heart disease) and a 31% reduction in death because of breast cancer compared with women who didn’t exercise. Men with prostate cancer who exercised were 37% less likely to die compared with men who didn’t exercise, and 27% less likely to die of prostate cancer. Research has found similar results for people with lung and colorectal cancer.
How does exercise improve outcomes in people with cancer? It is hypothesised that exercise enhances the immune system’s ability to monitor the body for cancer and eliminate it, reduce inflammation, and make the areas where cancer cells settle less hospitable.
How much should you exercise? I would follow the guidance from the colon cancer study and engage in at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity activity per week, and moderate-intensity muscle-strengthening activities at least two days per week for each major muscle group.
Most studies looking at the beneficial effects of diet on cancer outcomes have focused on people with breast or colorectal cancer.
In the Women’s Intervention Nutrition Study (WINS), almost 2500 women with early-stage breast cancer that had been surgically resected were randomly assigned to a dietary intervention designed to reduce fat intake or to their usual diet. Those assigned to a lower-fat diet had a 24% lower chance of breast cancer recurrence five years later. (The researchers note that weight loss as a result of the diet modifications could partly explain the reduced risk.)
Another analysis of over 9200 breast cancer survivors showed that those who ate diets high in fruits, vegetables and whole grains and low in red meats, fats and saturated fats, and oils reduced their mortality by 23%. In multiple studies looking at diet and colorectal cancers, those who adhered to a similar Mediterranean-style diet lowered their chance of dying by almost 50%.
For other types of diets, the data is more sparse. Consequently, in a systematic review from the American Society of Clinical Oncology, the authors felt there was insufficient evidence in favour of or against restrictive diets, such as ketogenic diets, low-carbohydrate diets, low-fat diets, functional foods or fasting to improve quality of life, treatment side effects or cancer control.
My take on diet, exercise and behavioural modifications is that as much as a cancer diagnosis can make you feel a loss of control, there are aspects of your health that you can adjust, and in so doing be an agent of change to improve your own outcomes.