 "Study in Lancet – Firstpost")
Bowel cancers are rising among younger persons aged 25-49 as compared to older adults, according to a new study published in Lancet.
The findings are notable because cancer has traditionally been associated with advanced age. Therefore, the increasing instances of cancer among younger people is a cause of concern.
In their paper titled ‘Colorectal cancer incidence trends in younger versus older adults: an analysis of population-based cancer registry data’, the researchers found that a number of countries have reported a rise in colon cancer among younger people and a decline in older people, suggesting that screening measures for older people are working and need to be adapted by younger people as well.
What is bowel cancer?
Bowel cancer is more formally referred to as colon or colorectal cancer.
The colon cancer affects colon that takes food from the stomach to the rectum. Colon cancer stems from pre-cancerous bumps called polyps in colon that can develop into cancerous tumours. They can be identified in screening and treated before reaching advanced stage.
In the United States, colon cancer is the third most common form of cancer and second most common cause of cancer-related death.
While the Lancet study is much more data-driven and covers several countries, the fact that colon cancer has been rising among younger people has been known for a while.
The Cleveland Clinic notes on its website that while colon cancer typically affects people over 50, the number of people aged 20-49 have reported a rise of colon cancer cases by 1.5 per cent a year for the past 15 years.
While the exact causes of colon cancer are not known, it is known that certain lifestyle choices affected the chances of developing colon cancer, such as smoking, obesity, eating too much red meat and processed food, and having a sedentary lifestyle.
Screening, awareness key to detect & treat colon cancer early: Study
Of the 50 countries and territories covered by researchers in the Lancet study, they found that early onset of cancer (among people aged 25-49) was increasing in 27.
In 20 of these 27 countries, the researchers found that the rise was either exclusive among 25-49 age group or faster than the increase in older adults.
The findings underscore the need for intensified efforts to identify factors driving these trends and increase awareness to help facilitate early detection, says the study.
The incidence rate of early-onset colon cancer was highest in Australia, the United States, New Zealand (14·8 [14·0–15·6]), and South Korea, and lowest in Uganda and India, according to the study.
In the most recent 10 years, incidence rates of early-onset colon cancer increased in 27 countries with the greatest annual increases in New Zealand, Chile, Puerto Rico, and England, according to the study.
The reducing risk among older adults may be attributable to declining smoking habits or widespread use of cancer screening.
The study found that the rise in colorectal cancer was confined to the younger age group (25–49 years) in 14, primarily high-income, Western countries: Australia, Canada, France, Germany, Ireland, New Zealand, Norway, Slovenia, England, Scotland, the United States, Argentina, Israel, and Puerto Rico.
While previously it was thought to be a concern in high-income Western countries, the study found that the trend has extended to diverse economies and countries in eastern Europe, Asia, Latin America, and the Caribbean.
Australia, Canada, New Zealand, and the USA, were historically the highest-risk countries for colon cancer and among the first to report a rise in early-onset disease as opposed to the rapid declines observed in older adults, noted the study.
As sedentary lifestyle and consumption of processed food or alcohol often comes up with more disposable income, the rising cases are seen more in either developed nations or nations developing faster. The study found that Chile, which has sustained steady economic growth over last decades and outperformed its neighbours, has shown the fastest increase in early-onset colon cancer in Latin America and the Caribbean.
The study referred to evidence from the United States where an increase of 5-unit increase in body mass index (BMI) measured at age 18 years was associated with a 20 per cent increased risk of early-onset colon cancer.
The study further noted that “a considerable shift from traditional diets, rich in low-fat and high-fibre foods, to increased consumption of red or processed meat, sugars, and ultra-processed convenience foods has probably contributed” at least partially to the rising cases of colon cancer. This is what might be driving the surge in South Korea and Japan where the study says meat-eating saw a 19 and 7-times increase during 1961-2021 respectively.
Even though early screening of colon cancer is recommended, there are practical constraints, such as costs and the possibility of screening of younger people disproportionately diverting the resources meant for older adults who are still more prone to cancers. This means that screening is used judiciously among younger adults and healthcare providers rely on signs and symptoms instead.
Most early-onset of colon cancers are diagnosed through symptoms often at an advanced stage and thus improving awareness among healthcare providers and the public about the signs and symptoms of early-onset colon cancer —rectal bleeding, abdominal pain, altered bowel habits, and unexplained weight loss— remains a primary opportunity for early detection and treatment, according to a study.
Moreover, the study says that prioritising the collection of family cancer history can be a key strategy for identifying individuals at higher risk for early-onset colon cancer, particularly among siblings and relatives of those with early-onset colon cancer. The Lancet study referred to a separate study as finding that half of early-onset colon cancer would be diagnosed earlier and up to 16 per cent potentially prevented if colonoscopy was performed at the age recommended by family history-informed guidelines.
