Colorectal cancer, which develops in the large intestine, begins with small, noncancerous clump of cells, known as polyps, that form on the inside of the colon and turn cancerous over time. Regular screening tests can help prevent the disease by identifying these polyps so they can be removed.

But not everyone is screened early enough — and a new study underlines the importance of taking family histories of the disease into account.

The study, published Monday in the journal Cancer, concluded that almost all adults included in the scientists’ analysis, who were diagnosed with colorectal cancer between 40 and 49 years of age, could have been diagnosed earlier if they had been screened according to current family history-based screening guidelines.

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Family history of the disease is one of the most important risk factors for colorectal cancer. People with a parent, sibling, or child who was diagnosed with colorectal cancer have two to four times the risk of developing the cancer compared to people without a family history, according to American Cancer Society.

It’s recommended that individuals with an average risk of colorectal cancer consider screening around age 50. But people with a higher risk should consider getting screened even sooner.

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Along with his colleagues, Samir Gupta, lead author of the research and professor of clinical medicine at the University of California, San Diego, conducted an analysis of the information in the Colon Family Registry on individuals aged 40 to 49 years. The dataset covered a long period of time, 1998 through 2007.

The investigators found that 25% of patients with colorectal cancer and 10% of those without colorectal cancer met the criteria for family history-based early screening. Almost 98% of patients with colorectal cancer, who met the early screening criteria, should have been screened at a younger age than when their cancer was diagnosed, meaning that their cancer could’ve been diagnosed earlier or even prevented — if they had taken heed of early screening guidelines based on family history.

“Colon cancer has strong genetic and environmental components… about 20% of people who get diagnosed with colon cancer will report some sort of family history of colon cancer,” said Gupta.

Gupta said early detection is so important when it comes to a disease like colorectal cancer because “one can go from being cured with a relatively straightforward surgery to other forms of treatments, such as chemotherapy, which has worse outcomes.”

That advice is good in theory, said Jeffrey Meyerhardt, medical oncologist and co-director of colon and rectal cancer center at Dana-Farber Cancer Institute. But Meyerhardt said, there’s no uniform way of ensuring that all health care providers are not only asking patients for their family history as a part of standard practice, but that this information is updated over time in medical records.

“Our family history is constantly changing and it’s not stagnant, so the question is about findings ways that physicians can incorporate that in their practice,” said Meyerhardt.

Meyerhardt emphasized the importance of increasing public awareness of the risk factors for colorectal cancer, alongside efforts to ensure individual medical records are updated with any sign of family history.

“There are probably family members that don’t fully tell their family about their [medical] history…. You probably would imagine that colorectal cancer was known to other relatives, but for benign polyps, it won’t be relayed to family members,” said Meyerhardt.

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