Cancer investigation and referral guidelines may need updating given the incidence of colorectal, breast, kidney, pancreas and uterine cancer is increasing in younger age groups.

A Rapid Review paper in the British Journal of Cancer said there was growing evidence that young people with cancer were more likely to experience diagnostic delay.

For example, UK guidelines use age as a key criterion to determine which patients require urgent investigation for suspected cancer.

“An increase in the incidence of cancer in younger patients may mean that the predictive value of symptoms may be higher than previously estimated,” the paper said.

The Review identified 98 registry-based studies published from 1995 describing age-related incidence trends in 12 cancers that have a minimum age threshold for investigation in the UK NICE cancer referral guidelines.

There was consistent evidence of an increasing incidence of colorectal, breast, pancreas, kidney and uterine cancers in young age groups.

However the incidence of lung, laryngeal and bladder cancer, all known to be associated with smoking, was found to be decreasing in all age groups and particularly in younger age groups.

There was inconclusive evidence for any change in incidence in stomach, oesphageal and ovarian cancers and myeloma.

The Review found a significant increase in both colon and rectal cancer in under-50s in both men and women in contrast to a decreasing incidence in older-age groups.

“Noticeably, some of the studies suggest that younger colorectal cancer patients often present with more aggressive diseases than older ones,” the Review said.

“The robust evidence of an increase in colorectal cancer incidence in younger people in North America, Europe and Oceania, calls for a re-evaluation of the age threshold for the referral of symptomatic patients.”

Breast cancer incidence increased modestly in under 50s but had a larger increase in women aged 20–29 years.

“Further research should also determine the causes behind the rise to disentangle real generational effects to those due to changes in clinical practice, increase testing and overdiagnosis,” the Review said.

The incidence of kidney cancer increased in all age groups and in both genders but with a steeper rise in younger patients.

The Review said that obesity, which has become more prevalent in high-income countries, is a known risk factor for colorectal, pancreas, kidney, and uterine cancer.

“Variations in patterns of childbearing and breastfeeding or increase use of oral contraception may be contributing to the rise in breast and uterine cancer incidence in younger generations,” it said.

“Clarifying the role of preventable causes will help underpin more effective population health policies aimed at cancer prevention.”

The Review noted that the development of new highly sensitive and specific testing modalities had to be factored into cost-benefit evaluations of lowering referral or screening age thresholds.

An Australian co-author on the paper Dr Rebecca Bergin, a health services researcher at Cancer Council Victoria, said the increasing incidence of some cancers in younger people meant we might need to revisit some of the recommendations for urgent referral.

“We have some of that for colorectal cancer. If the incidence is increasing in this younger age group, then we might want to have a look at risk profiles for people presenting with certain symptoms who need quicker referral,” she said.

“Certainly the screening debate is a live one in Australia at the moment. In the US they have moved to lowering that age … here though there is still a bit of uncertainty about the cost effectiveness, the capacity of colonoscopy that we have at the moment, the benefits and risks of screening in a slightly younger population.”

She said the slightly lower threshold for CRC screening in the US — from 50 to 45 years — still leaves the question about how to identify even younger people.

Dr Bergin said as well as work on risk prediction tools to help identify younger people with cancer, there was a body of work around why this is happening and how to mitigate risk.