Younger patients with metastatic colorectal cancer represent a high-risk group that is less likely to respond to treatment. Colorectal cancer in patients younger than 40 years is more likely to grow despite treatment. Further, younger patients are at greater risk of death compared with people in other age groups. This research was presented at the 2013 European Cancer Congress in Amsterdam, The Netherlands.

An analysis of 20,034 patients in 24 phase III clinical trials showed that the youngest and oldest patients had the highest risk of disease progression and death, compared with middle-age patients. Compared with 57-year-old patients, people younger than 40 years had a 30% increased risk of dying from the disease, and they had a 28% increased risk of their disease spreading during the first year of follow-up compared with 61-year-old patients.

Colorectal cancer occurs in 4.6% of patients who are younger than 50 years, and the incidence of the disease in this age group increased at a rate of 1.5% per year from 1992 to 2005. The most dramatic increases were observed in the 20-to-29-years group , with an increase in cases of 5.2% annually in men and 5.6% annually in women. Among those 30-to-39-years, the annual increases in cases was 3% in men and 2% in women.

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“The reasons why the incidence of colorectal cancer is increasing in younger patients remain unknown; although genetic predisposition, environmental factors, fewer early cancer detections in this population, or a combination of these factors are thought to play a role,” said investigator Christopher Lieu, MD, of Colorado University (CU) Cancer Center and CU’s School of Medicine in Aurora.

“We carried out this study to see whether age was associated with time until cancer progresses or the patient dies. We also wanted to get a better picture of the age-response relationship and identify how risk changes as people age, rather than simply comparing one group (patients younger than 40 [years]) with another group (patients older than 40 [years]),” Lieu said.

Previous studies in this field split the population into two mutually exclusive groups, establishing rigid limits between those patients younger than 40 or 50 years and those older. The new research, however, did not use such a cut-off approach and includes data spanning all ages.

“The reason we did this is we believe a 49-year-old patient with colorectal cancer may be different than a 20-year-old. By including them in the same group of people younger than 50 years old, we might be mistakenly considering them the same,” said Lieu.

“Analysis of this incredibly large population of patients has allowed us to answer meaningful questions, such as the outcomes of young versus older patients. Our results show young age is associated with worse overall survival and progression-free survival,” said Lieu. “Young patients with metastatic colorectal cancer represent a group who are at high risk for treatment failure.”