Early-Onset Bowel Cancer

Written by A/Prof Viraj Kariyawasam, Gastroenterologist

1. What is Early-Onset Bowel Cancer?

Early-onset bowel cancer refers to colorectal cancer diagnosed in people under the age of 50. Traditionally, bowel cancer was considered a disease of older adults, but in recent years there has been a concerning increase in cases among younger people.

Importantly, while overall bowel cancer rates are falling in older, screened populations, rates are rising in younger adults who are not routinely included in national screening programs.

Australian data show a clear increase in bowel cancer in people under 50. The Australian Institute of Health and Welfare (AIHW) reports that the early-onset colorectal cancer incidence rate rose from about 7 per 100,000 people in 2000 to an estimated 12 per 100,000 in 2024. Over the same period, the share of all bowel cancer cases diagnosed in people under 50 increased from around 8% (2000) to about 13% (2024).

Cancer Australia reports rising age-specific rates across younger age groups. Between 2000 and 2025, incidence increased from 2.2 to an estimated 4.6 per 100,000 (ages 20–29), from 6.3 to an estimated 19 per 100,000 (ages 30–39), and from 25 to an estimated 31 per 100,000 (ages 40–49).

International studies show similar patterns. Global analyses report that early-onset colorectal cancer cases have nearly doubled since 1990, and multi-country registry studies show sustained year-on-year increases, particularly in adults aged 20–39. These trends reinforce the importance of not dismissing symptoms based on age alone

2. Symptoms & How It May Present

Symptoms of bowel cancer in younger people are often similar to those in older adults, but are more likely to be overlooked or attributed to benign conditions.

Common symptoms include rectal bleeding, persistent change in bowel habits, abdominal pain, iron deficiency anaemia, fatigue, unexplained weight loss, or a feeling of incomplete bowel emptying.

3. Why Diagnosis Is Often Delayed

Diagnosis of bowel cancer in younger people is frequently delayed because symptoms may be attributed to haemorrhoids, irritable bowel syndrome, stress, or dietary issues.

Younger patients may also delay seeking medical advice, and clinicians may have a lower initial suspicion of cancer due to age alone.

4. Expert Commentary

A/Prof Viraj Kariyawasam, Gastroenterologist, has highlighted in recent national media that bowel cancer in younger people is often diagnosed at a more advanced stage because symptoms are missed or ignored.

“We are seeing more younger patients with bowel cancer, and too often their symptoms have been present for months or even years before diagnosis. Bleeding, iron deficiency, or persistent bowel changes in younger adults should never be dismissed simply because of age.”

5. How Is Early-Onset Bowel Cancer Diagnosed?

Diagnosis is the same regardless of age. Colonoscopy is the most accurate test for detecting bowel cancer and allows biopsy of suspicious areas.

Blood tests may reveal iron deficiency or anaemia, and imaging such as CT scans is used once cancer is diagnosed to assess extent and guide treatment.

6. Prevention & Risk Reduction

Awareness is the most important preventive strategy for early-onset bowel cancer. Recognising symptoms early and seeking prompt medical assessment improves outcomes.

Maintaining a healthy weight, regular exercise, a fibre-rich diet, limiting alcohol intake, and avoiding smoking may reduce risk. People with a family history or genetic risk should discuss earlier screening with their doctor.

7. When to Seek Medical Advice

Any person, regardless of age, should seek medical advice for rectal bleeding, persistent bowel habit changes, unexplained weight loss, abdominal pain, or iron deficiency anaemia.

Early investigation saves lives. Age alone should never be a barrier to appropriate testing.