Bowel cancer has risen significantly among New Zealanders under 50 over the past two decades, a study has found.
Surgeon Dr Jamish Gandhi says the increase was across the various types of bowel cancers and in both males and females.
He says it's a concern and warrants greater attention and investigation.
Among under-50s, distal colonic cancer in men increased by 14 percent per decade, while rectal cancer rose 18 percent in men and 13 percent in women per decade.
"There were reductions in bowel cancer rates in patients between the ages of 50 to 79 across certain cancers," Dr Gandhi said.
"However, the incidence rate continued to grow once again once people turned 80."
Previously based in New Zealand and now at Royal Adelaide Hospital, Dr Gandhi presented his findings to the Royal Australasian College of Surgeons' annual scientific conference in Adelaide.
The study's data came from the National Cancer Registry and was linked to population statistics from 1995 to 2012.
Bowel cancer is also known as colorectal cancer and covers all cancers of the colon, rectum and large bowel.
Dr Gandhi said people needed to be aware of the risks factors and what signs to look for, as early detection was critical.
New Zealand has one of the world's highest bowel cancer rates, with Ministry of Health figures showing that each year about 3000 new cases are diagnosed and 1200 people die from the disease.
Since late 2011, the government has offered screening to eligible residents in the Waitemata District Health Board area as part of a pilot programme.
A National Bowel Screening Programme will be progressively rolled out across the country from 2018.