It is estimated that there are currently over a million Canadians who have survived cancer, a number that will increase dramatically over the next few years as treatment continues to improve and the population ages. In addition to the physical and psychological consequences that can result from treatment, cancer survivors in many cases still have a high risk of recurrence, especially for certain types of cancer that are very difficult to treat (for example, lungs, colon or esophagus).
However, studies show that it is possible in several cases to reduce the risk of these relapses by adopting good life habits, especially the absence of tobacco, a plant-rich diet, maintaining a normal body weight and regular physical activity.
Another risk that cancer survivors face, less known, is the development of another primary cancer, that is, one that affects another organ in the body. Unlike the recurrence of the first cancer, these second cancers can be caused by a person’s genetic predisposition to develop cancer, which will be a consequence of the treatments used to treat the first cancer (carcinogenic mutations caused by chemotherapy and / or radiotherapy, for example) or even bad life habits that were responsible for the first cancer (smoking, obesity, alcohol abuse, physical inactivity) (1).
According to recent research, of all these possibilities, it is the lifestyle component that plays the most important role in the development of another cancer (2).
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 had a higher risk of developing other cancers, primary (11% in men and 10%). % in women) and an even higher risk of dying after diagnosis (45% in men and 33% in women).
These risks of developing second primary cancer were higher by 18 of the 30 most common primary cancers in men and by 21 of the 31 most common primary cancers in women.
Smoking and obesity
It is remarkable that most of this excess risk appears to stem from lifestyle risk factors that are common to the first and second primary cancers. For example, the risks of second cancer caused by tobacco were higher in survivors of the first cancer associated with smoking, and these cancers accounted for a large percentage of the second cancer listed in the study.
Studies show that a large percentage of cancer survivors from smoking continue to smoke and that there is therefore a high risk of developing another tobacco-related cancer. Thus, four cancers mainly caused by tobacco (lung, bladder, oral cavity / esophagus and esophagus) accounted for 26% of all other cancers and 45% of associated mortality. Lung cancer alone accounts for a third of all cancer deaths.
The study also shows that many obesity-related cancers survivors had a high risk of developing another cancer whose development is accelerated by being overweight.
Among the survivors of all early cancers, four cancers that are often associated with obesity (colorectal, pancreas, uterus, and liver) accounted for about 35% of total mortality from other cancers. This is consistent with previous studies that have shown that survivors of breast cancer and colorectal cancer have a higher risk of developing another cancer associated with obesity.
Despite the trauma caused by a cancer diagnosis, studies show that most people affected by the disease do not change their habits significantly and therefore there are many survivors who remain at high risk of being re-affected by either their cancer recurrence or other different cancers.
For example, in the United States, as many as 12% of cancer survivors are smokers, 67% are overweight, including 32% are obese, and 34% do not engage in regular physical activity.
The potential for preventing this other cancer is therefore huge: instead of being discouraged from thinking that it is too late and there is no point in changing your lifestyle, you can raise the bar and fundamentally change these habits to improve your chances of survival. Eating plenty of plants, physical activity and maintaining a normal body weight are daily actions that can reduce the risk of recurrence and significantly improve a healthy life expectancy.
- (1) Travis LB et al. Etiology, genetics, and prevention of secondary neoplasms in adult cancer survivors. Nat. Rev. Clin. Oncol. 2013; 10: 289-301.
- (2) Sung H et coll. Association of First Primary Cancer with the Risk of Primary Cancer Among Adult Cancer Survivors in the United States JAMA 2020; 324: 2521-2535.