Younger patients with colorectal（结肠直肠的） cancer that has spread (metastasised) to other parts of the body represent a high-risk group that is less likely to respond to anti-cancer treatments. Their disease is more likely to progress and they are at greater risk of death than other age groups, according to new research to be presented to the 2013 European Cancer Congress (ECC2013). An analysis of 20,034 patients in 24 phase III clinical trials for colorectal cancer, of which 695 patients (3%) were younger than 40, showed that the youngest and oldest patients had the highest risk of their disease progressing and of dying, compared to middle-aged patients. When compared to 57-year-olds, the youngest patients had a 30% increased risk of dying from the disease, and, when compared to 61-year-olds, they had a 28% increased risk of their disease progressing and metastasising during the first year of follow-up after randomisation and the start of treatment. The oldest patients had a 72% increased risk of death and a 19% increased risk of their disease metastasising compared to the 57 and 61-year-olds during the follow-up period.

Dr Christopher Lieu, MD, an assistant professor at the University of Colorado (USA), will tell the congress: "Although colorectal cancer occurs in only 4.6% of patients who are younger than 50, the incidence of the disease has been increasing at a rate of 1.5% per year from 1992 to 2005 in this age group. The most dramatic increases have been observed in the 20-29 year-old group, where there has been an annual 5.2% increase in cases in men and a 5.6% increase in women, and in the 30-39 year-old group, where there has been an annual 3% increase in men and a 2% increase in women.

"The reasons why the incidence 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. 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) with another group (patients older than 40)."

Previous studies in this field have split the population into two mutually exclusive groups, establishing rigid limits between those patients younger than 40 or 50 and those older than that age. The new research, however, did not use such a cut-off approach and it includes data spanning all ages. "The reason why we did this is because we believe that 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 to be the same," Dr Lieu will explain.