A large, current study from the USA with more than 1.5 million examined cases dealt with the influence of changeable lifestyle factors on the cancer risk of different tumor diseases. The findings shed light for the first time on how many cancer cases could actually be prevented with simple lifestyle changes.
The study by the American Cancer Society examined the data records of around 1.5 million tumor patients, including nearly 600,000 cancer-related deaths. All data came from the archives of the Centers for Disease Control and Prevention (CDC) and the National Cancer Institute (NCI). A total of 26 different tumor entities and 17 modifiable risk factors were examined. The latter included, for example, alcohol intake, active or passive smoking, extreme obesity, a low-fiber diet, high meat consumption, low consumption of fruit and vegetables, calcium deficiency, lack of exercise and frequent high UV exposure.
In addition, Dr. Farhad Islami and his team recorded six infections associated with cancer, namely HPV, HBV, HCV, HIV, herpesvirus type 8 and Helicobacter pylori.
In their analyses, however, Islami and colleagues did not limit themselves to the prevalence of risk factors and the resulting tumor diseases. Instead, they used meta-analyses to determine the associated relative risk that a changeable lifestyle factor has as a factor in leading to eventual tumor development.
The results of this study showed that 42% of all cancer cases and 45% of all cancer-related deaths were due to changeable risk factors. The first three risk factors were smoking, obesity and high alcohol consumption.
Smoking alone accounted for 19% of cancer cases and 29% of deaths. Obesity caused 7.8% of the tumors and promoted cancer-related death in 6.5% of those affected. Alcohol consumption, on the other hand, was still responsible for about 5.6% of tumor diseases and 4% of deaths. But even today's widespread lack of exercise led to a tumor in 2.9% of cases and to death in 2.2% of those affected.
The American study is also interesting because it shows which tumor entities are particularly influenced by which lifestyle factors. Thus, 86% of all lung cancers were caused by such variable factors as smoking (up to 82% of cases).
In addition, about 96% of melanomas of the skin are caused by excessive UV exposure, 60% of uterine tumors are caused by obesity and every second esophageal carcinoma is caused by smoking. Cigarette smoke was also associated with about 47% of bladder cancer cases. The researchers also found that one in ten colorectal tumors was caused by a lack of fiber-rich food.
If one considers the infections, such as those caused by human papillomaviruses, approximately 88% of the anal tumor lesions are positive for these partly carcinogenic viruses and still slightly more than a third of the oropharyngeal lesions in both sexes. In addition to cervical carcinoma, HPV also causes anal and oropharyngeal carcinomas. HPV 16 and 18 are the most common. The available monovalent HPV vaccine prevents infection with these viruses. Therefore, HPV-induced cervical, anal and pharyngeal cancers are considered preventable and therefore belong to the modifiable lifestyle factors.
The results of this current study clearly show how important and worthwhile it is to recommend and apply well-known prevention measures - including vaccinations, e.g. against HPV or HBV - in order to reduce cancer morbidity and mortality in the future.
The authors of the study highlight four key factors that each person should keep in mind individually: body weight, alcohol intake, nutrition and physical activity. These four factors combined accounted for up to 14% of the general cancer risk in women and 22% in men.
Therefore the authors recommend to inform about these connections and to recommend the well-known preventive health measures further to patients (e.g. smoking renunciation, vaccinations against HPV and HBV, weight reduction, sport,...). That sounds like an old story, but the recommendations are now at least backed up by new, well-founded figures.
1. Islami F et al., Anteil und Anzahl der Krebsfälle und Todesfälle, die auf potenziell veränderbare Risikofaktoren in den USA zurückzuführen sind. CA Krebs J Clin 2017; doi: 10.3322/caac.21440.
2. https://ww w.medicalnewstoday.com/artikel/320121.php