The rate of occurrence of pre-cancerous masses in the colon is the same for patients having an average risk regardless of their age between 40 to 60 years.
The present protocol recommends screening of patients aged 50 and above for colon cancer based on the increasing incidence of colon cancer at that age.
The researchers believe that their findings would help in screening of colon cancer onset at a younger age.
Because observational studies have shown that it takes a decade for pre-cancerous growths, or adenomas, to develop and progress to cancer, the increase in colon cancer prevalence in the over-50 age group, in fact, may be the result of undetected adenomas that were present in the individuals in their 40s.
The study led by Drs. Alfred I. Neugut and Andrew Rundle from Columbia University Medical Centre compared colonoscopy results, broken down by age group.
The team reviewed 553 screening colonoscopies for patients ages 40 to 49 and 352 screening colonoscopies for patients ages 50 to 59. Individuals who could be deemed "high-risk" because of a family history of colon cancer, a personal history of inflammatory bowel disease or any malignancy other than skin cancer were excluded from the sample.
They found that in 40 to 49 age group, 79 patients, or 14 percent, had one or more adenoma. Similarly, the 50 to 59 age group had 56 patients, or 16 percent, with one or more adenoma.
"Our results support the theory that adenomas, which later may lead to cancer, form at an age earlier than we screen for today," said Neugut, professor of medicine and epidemiology at Columbia University Medical Center and head of cancer prevention and control for the Herbert Irving Comprehensive Cancer Center of Columbia University Medical Center and New York-Presbyterian Hospital.
"With this information in hand, it is logical to think that if we were to recommend screening for colon cancer at age 40, we may be able to decrease its prevalence even further and save more people from having to battle the disease," he added.
Though the number of adenomas was relatively similar in the two age groups, there was a doubling in the prevalence of abnormal cell growth, or advanced neoplasia, in the 50 to 59 age group than the 40 to 49 age group.
In the 40 to 49 age group, 11 patients, or 2 percent, had an advanced neoplasm, and in the 50 to 59 age group, 13 patients, or 4 percent, had an advanced neoplasm.
"What this implies is that while the number of pre-cancerous growths is very similar in both age groups, there is a progression toward cancer in older patients," said Andrew Rundle, DrPH, assistant professor of epidemiology at Columbia's Mailman School of Public Health.