It is estimated that there are currently more than 1 million Canadians cancer survivors, a number that will increase dramatically over the next several years as treatment continues to improve and ages. In addition to the physical and psychological consequences that can result from treatment, cancer survivors in many cases remain at risk of recurrence, particularly because certain types of cancer are difficult to treat (lung, colon, or esophagus, for example).
However, studies indicate that in many cases it is possible to reduce the risk of these relapses by adopting good lifestyle habits, especially not smoking, eating a diet rich in plants, maintaining a normal body weight and engaging in regular physical activity.
Another lesser known risk that cancer survivors face is developing another primary cancer, that is, cancer that affects another organ in the body. The cause of these second cancers, which differs from the recurrence of the first cancer, can be due to a person’s genetic predisposition to cancer, and are the result of the treatments used to treat the first cancer (cancerous mutations caused by chemotherapy and / or radiotherapy, for example) or even as a result. For the same bad lifestyle habits that were responsible for the first cancer (smoking, obesity, alcohol use, physical inactivity) (1).
According to a recent study, among all these possibilities, it is the lifestyle component that plays the most important role in the development of a second cancer (2).
By analyzing data collected from 1.5 million adult cancer survivors between 1992 and 2017, the researchers noted that, compared to the general population, adult cancer survivors are more likely to develop a second cancer. Primary (11% in men and 10% in women) and the risk of death after diagnosis is higher (45% in men and 33% in women).
The risk of developing a second primary cancer was higher in 18 of the 30 types of primary cancers that are most common in men and 21 of the 31 types of primary cancers that are most common in women.
Smoking and obesity
Remarkably, most of these increased risks appear to stem from the lifestyle-related risk factors that share the first and second primary cancers. For example, the risks of developing a second cancer caused by tobacco were higher in survivors of the first smoking-related cancer, and these cancers were responsible for a large proportion of the second cancers included in the study.
Studies show that a high percentage of smoking-related cancer survivors continue to smoke, and thus they are at risk of developing another tobacco-related cancer. Thus, four cancers mainly caused by tobacco (lung, bladder, oral cavity / pharynx and esophagus) accounted for 26% of all second cancers and 45% of associated deaths. Lung cancer alone accounts for a third of deaths from second cancers.
The study also shows that survivors of several obesity-related cancers were at a high risk of developing second cancers whose development is known to accelerate due to weight gain.
Among survivors of all early cancers, four types of cancers associated with obesity (colon, rectum, pancreas, uterus and liver) were responsible for about 35% of all deaths from second cancers. This is in agreement with previous studies that have shown that in breast and colorectal cancer survivors, the risk of developing a second cancer associated with obesity was higher in people who were overweight.
Give a boost
Despite the shock that a cancer diagnosis causes, studies show that the majority of people with the disease do not significantly change their habits, and thus there are many survivors who remain at risk of contracting the disease again. Either by recurring cancer or by the emergence of a distinct second cancer.
For example, in the United States, up to 12% of cancer survivors are smokers, 67% are overweight, including 32% are obese, and 34% do not participate in regular physical activity.
Thus, the potential to prevent these second cancers is enormous: instead of being discouraged by a cancer diagnosis with the belief that it is too late and that there is no point in changing your lifestyle, you can on the contrary raise the bar and change these habits radically to improve your chances of survival. Eating plenty of plants, being physically active and maintaining a normal body weight are all daily actions that can reduce the risk of recurrence and significantly improve life expectancy.
- (1) Travis LB et al. Etiology, genetics, and prevention of secondary neoplasms in adult cancer survivors. Nat. Reverend Klein. Oncol. 2013; 10: 289-301.
- (2) Sung H et coll. Association of first primary cancer with subsequent primary cancer risk among cancer survivors in adults in the United States. Gamma 2020; 324: 2521-2535.