Younger, fatter, colorectal cancer

12. September 2017
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Anyone who in previous times had been diagnosed with colon cancer at an early age was considered an exceptional case. American studies now show that more and more young adults are affected by the disease. An explanation might be obesity during teenage years.

Even in the 1970s having colon cancer before the age of 50 was considered an exceptional case. This has changed: US studies show that more and more young adults are affected by the disease. What’s more rectal cancer is also more common among people between 30 and 50 years of age. One reason for this could be the increased number of heavily overweight adolescents.

Colon cancer risk doubled in 40 years

An American study published in February 2017 showed: those who were born in 1990 have twice as high a risk of colon cancer as those born around 1950. The risk of falling victim to rectal cancer is even four times as high for those born in the 1990s. At present about 3 out of 10 people in the US who have been diagnosed with rectal cancer are younger than 55.

Rising incidence among people under 50 years of age since 1986

The study recorded colon cancer incidence from 1974 to 2013 and used data from 490,305 adults with colon cancer in the SEER database (Surveillance, Epidemiology and End Results). Before the early 1980s the incidence for people under 50 years of age fell – however for people over 50 it rose. From 1986 onwards, the study period saw a trend reversal: from this point in time until the end of the observation period in 2013, the incidence of colon cancer among persons older than 55 decreased. For the 20 to 29 year-olds, however, it increased by 2.4% per year, among the 30 to 39 year-olds by 1% per year.

Even more dramatic was the situation for younger adults with rectal cancer: here an increase in the number of cancer cases for young adults was already observed at the beginning of the observation period (starting in 1974). The incidence per year among the 20 to 29 year-olds thus increased by 3.2%.

Awareness campaigns for doctors and patients promoted

The logical consequence for the study authors is that “we need education campaigns for physicians and for the population which point out that colon cancer is also an issue for younger adults”, Rebecca Siegel, head of studies at the American Studies Cancer Society, says. Early diagnoses are particularly effective and important with young people for successful therapy. In order to counter the trend of early diseases, Siegel proposes a comprehensive clarification campaign, which emphasises the importance of health nutrition and active lifestyle. Moreover, the minimum age for cancer screening should be reconsidered. In addition to tobacco smoke, being overweight and a low-fibre diet are the main risk factors for the development of colon cancer.

Israeli soldiers’ recruitment service delivers valuable health data

A study from Israel confirms that obesity during adolescence could be one of the main risk factors for colon cancer before one’s 50th birthday. In Israel compulsory military duty exists for all young men and women. Between 16 and 19 years of age, mostly at age 17, body size and weight are recorded during the course of the examination. Scientists from the University of Tel Aviv now have the body-measure index of 1,087,358 men and 707,212 women who were enlisted from year 1967 to 2002. They compared the figures to later entries in the cancer register of the country; in Israel all colon and rectal cancer cases are recorded.

During the median observation period of 23 years, 1,977 men and 990 women were diagnosed with colon cancer. To an above average extent many of those affected were overweight or obese at the time of the screening. For overweight or obese adolescents this resulted in a 50% increase in the risk of colon cancer when aged less than 50. With rectal cancer the numbers were still more frightening: overweight male teenagers had a risk of about 70% increase, with overweight girls this even amounted to a 100% increased risk.

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Carrying body fat could be a major risk factor for the development of colon cancer. In the countries marked in dark-green, every third woman is already obese.

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In the countries marked in dark green, about every third man is already obese.

However, the Israeli study has a few weaknesses: Firstly, it cannot elucidate the factors (such as lack of exercise, metabolic disorders or nutritional parameters) which had led to young people to having excess body weight or obesity, and which are responsible for the development of cancer. On the other hand, at the end of the observation period the participants were only on average 49 years old and had not yet reached the age limit for colon cancer. The data situation could thus change over the next few years and the observed associations could thus prove to be no longer conclusive. The study also did not record any familial predispositions.

Sources:

Colorectal cancer incidence patterns in the United States, 1974-2013;
Rebecca L. Siegel et al.; AJ Natl Cancer Inst, doi: 10.1093/jnci/djw322; 2017

Adolescent body mass index and risk of colon and rectal cancer in a cohort of 1.79 million Israeli men and women: A population-based study.
Zohar Levi et al.; Journal of the National Cancer Institute, doi: 10.1002/cncr.30819; 2017

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