# Early-onset colorectal cancer (under 50)

Source: https://onco.cc/cancers/early-onset-colorectal/  
OnCo record `early-onset-colorectal` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Bowel cancer is rising in people under 50, for reasons that are still not understood, and it is usually found late because neither patients nor doctors expect it. Treatment is the same as in older adults and works as well stage for stage; the changes are earlier screening, genetic testing for everyone diagnosed young, and attention to fertility, work and family.

## Summary

Early-onset colorectal cancer is defined by age under 50 at diagnosis. Birth-cohort analyses (Siegel and colleagues, 2017) showed that people born around 1990 have double the colon cancer risk and four times the rectal cancer risk of those born around 1950 at the same age, a rise seen across high-income countries and attributed to diet, obesity, antibiotics, the microbiome and other early-life exposures without any one cause proven; a colibactin mutational signature from pks-positive Escherichia coli acquired in childhood is enriched in early-onset tumours (Nature 2025). About one in six patients diagnosed under 50 carries a germline cancer-predisposition variant, half of them Lynch syndrome, so multigene germline testing is recommended for everyone in this group.

Most early-onset tumours are left-sided or rectal, microsatellite-stable and diagnosed at stage III or IV after months of rectal bleeding, iron deficiency or change in bowel habit that was attributed to haemorrhoids or irritable bowel. Stage for stage, outcomes are similar to older adults, and treatment follows the same pathways: surgery and stage-based adjuvant chemotherapy, total neoadjuvant therapy or organ preservation for rectal tumours, and genotype-directed therapy for metastatic disease. Young patients receive more intensive chemotherapy without evidence that it helps them more.

The policy response has been earlier screening: the American Cancer Society lowered the starting age for average-risk adults from 50 to 45 in 2018 and the US Preventive Services Task Force followed in 2021; European programmes are debating the same step, and polygenic risk scores may set individual starting ages. For patients, the distinct needs are fertility preservation before pelvic radiotherapy and oxaliplatin, sexual and stoma counselling, financial and employment support, and enrolment in the cohort studies trying to explain the rise.

## Fields

- Kind: Cancer
- Last checked: 2026-09-17
- Also known as: Young-onset colorectal cancer; Colorectal cancer in adults under 50; Early-age-onset colorectal cancer; Bowel cancer in young adults; Early-onset colorectal cancer; EOCRC
- Tags: subtype-page
- Group: gastrointestinal
- Burden: Roughly one in ten colorectal cancers in high-income countries is now diagnosed before 50, and incidence in this age group has risen by about 2 percent a year in the United States since the mid-1990s while falling in older adults; most are left-sided or rectal and diagnosed at a later stage.
- Subtypes: Sporadic early-onset colorectal cancer (the large majority; mostly left colon and rectum, microsatellite-stable); Hereditary early-onset colorectal cancer (Lynch syndrome, familial adenomatous polyposis and other germline variants, about one in six); Early-onset rectal cancer (fertility, sexual function and stoma questions loom larger); Mismatch-repair deficient early-onset tumours (immunotherapy as in other dMMR disease)
- Biomarkers: Multigene germline panel for every patient diagnosed under 50; Mismatch repair / microsatellite status; RAS, BRAF V600E and HER2 as for all colorectal cancer; Colibactin (pks+ E. coli) mutational signature (research); Iron deficiency and rectal bleeding as presenting signs at any age

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/early-onset-colorectal/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/early-onset-colorectal/#overview [3 state-of-the-art points]
- Types and stages (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/early-onset-colorectal/#what-it-is [4 subtypes]
- Symptoms and diagnosis (on the hub): How this cancer shows itself, how the diagnosis is confirmed, and the biomarkers clinicians test for. https://onco.cc/cancers/early-onset-colorectal/#finding-it [5 biomarkers]
- Treatment (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/early-onset-colorectal/#treating-it [5 settings, 4 decisions with options]
- Trials and papers (on the hub): Trials recruiting now, the landmark trials, the trials held by this cancer's subtypes, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/early-onset-colorectal/#evidence [4 trials, 8 key papers, 5 milestones]
- Biology and targets (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/early-onset-colorectal/#science [6 targets, 1 pathway]
- Countries and centres (own page): Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes. https://onco.cc/cancers/early-onset-colorectal/where-you-are/ [1 centre, 29 UK centres]
- Decisions and support (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/early-onset-colorectal/#living-with-it [19 questions, 6 red cards]
- Pipeline and open problems (own page): Everything in development, the medicines held by this cancer's subtypes, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/early-onset-colorectal/coming/ [10 medicines, 6 ideas, 4 open problems]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/early-onset-colorectal/data/ [75 connected records, 2 notes]

## Standard of care

- Screening and early diagnosis: Average-risk screening from age 45 (colonoscopy, faecal immunochemical test, stool DNA or blood test); earlier and more frequent colonoscopy for family history or a known syndrome; investigate rectal bleeding and iron deficiency promptly at any age. ([Colorectal cancer screening (colonoscopy, FIT, stool DNA, blood)](https://onco.cc/technologies/colorectal-screening/), [Faecal immunochemical test (FIT)](https://onco.cc/terms/fit-test/), [Colonoscopy](https://onco.cc/terms/colonoscopy/), [Shield](https://onco.cc/drugs/shield/), [Cologuard](https://onco.cc/drugs/cologuard/))
- Diagnosis and staging: Germline multigene testing for every patient; mismatch repair, RAS, BRAF and HER2 testing; fertility counselling before treatment. ([Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/), [Lynch syndrome](https://onco.cc/terms/lynch-syndrome/), [Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)](https://onco.cc/terms/msi/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/))
- Localised disease: As for colorectal and rectal cancer by stage: surgery, adjuvant FOLFOX or CAPOX for stage III, total neoadjuvant therapy or organ preservation for rectal tumours; no escalation on the basis of age alone. ([FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [Total neoadjuvant therapy (TNT, rectal cancer)](https://onco.cc/terms/total-neoadjuvant-therapy/), [Organ preservation (watch-and-wait, bladder-sparing, larynx preservation)](https://onco.cc/terms/organ-preservation/), [RAPIDO](https://onco.cc/trials/rapido/))
- Metastatic disease: Genotype-directed therapy as for all metastatic colorectal cancer: checkpoint blockade if mismatch-repair deficient, encorafenib-cetuximab for BRAF V600E, HER2 or KRAS G12C combinations, otherwise chemotherapy with bevacizumab or an anti-EGFR antibody by sidedness. ([Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Encorafenib](https://onco.cc/drugs/encorafenib/), [Tucatinib](https://onco.cc/drugs/tucatinib/), [Sotorasib](https://onco.cc/drugs/sotorasib/), [Bevacizumab](https://onco.cc/drugs/bevacizumab/), [Cetuximab](https://onco.cc/drugs/cetuximab/))
- Survivorship: Structured exercise (CHALLENGE), long-term neuropathy and bowel function care, fertility and sexual health follow-up, financial and employment support. ([Exercise & lifestyle oncology](https://onco.cc/technologies/exercise-oncology/), [CHALLENGE (CCTG CO.21)](https://onco.cc/trials/challenge/))

## State of the art

- Screening now starts at 45 in the United States, the first policy response to the rise.
- Universal germline testing in patients under 50 finds a hereditary syndrome in about one in six.
- Mutational signatures are beginning to point at childhood exposures, including colibactin-producing bacteria.

## Open problems

- The cause of the rise is unknown; no exposure has been proven.
- Diagnostic delay in young adults with rectal bleeding remains long.
- Whether screening should start at 45, 40 or by individual risk is unsettled outside the United States.
- Fertility, sexual function and financial toxicity are poorly measured in trials.

## Notes

- The numbers as they stood in September 2026. The American Cancer Society's 2026 report gives incidence rising 3 percent a year in adults aged 20 to 49 over 2013 to 2022 and 0.4 percent a year at 50 to 64, against a fall of 2.5 percent a year in the over-65s, with mortality under 50 rising 1 percent a year since 2004; rectal cancer is now 32 percent of colorectal cancers, up from 27 percent in the mid-2000s. Registry data from 36 countries showed incidence in adults under 50 rising in 19 of them and, in nine spanning three continents, rising in the young while stable or falling in older adults (Siegel 2019).
- The leading mechanistic lead. In 981 colorectal cancer genomes from 11 countries, the colibactin mutational signatures SBS88 and ID18 were 3.3 times commoner in people diagnosed before 40 than after 70, were imprinted early in tumour development, and accounted for about a quarter of APC driver insertions and deletions in colibactin-positive cases, which points at an exposure to colibactin-producing gut bacteria in early life (Nature 2025).

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Colorectal_cancer
- Wikipedia: https://en.wikipedia.org/wiki/Colorectal_cancer
- NCCN Guidelines: Colon Cancer: https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1428
- Colorectal cancer statistics, 2026 (American Cancer Society, CA: a Cancer Journal for Clinicians): https://doi.org/10.3322/caac.70067
- Siegel, Gut 2019: global patterns and trends in colorectal cancer incidence in young adults (36 countries): https://doi.org/10.1136/gutjnl-2019-319511
- Nature 2025: geographic and age variations in mutational processes in colorectal cancer (981 genomes from 11 countries): https://doi.org/10.1038/s41586-025-09025-8

## Connected records

- cancers: [Adolescent and young adult cancers (ages 15 to 39)](https://onco.cc/cancers/aya-cancers/), [BRAF V600E-mutant colorectal cancer](https://onco.cc/cancers/braf-v600e-colorectal/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Familial adenomatous polyposis-associated colorectal cancer](https://onco.cc/cancers/fap-associated-colorectal-cancer/), [HER2-amplified colorectal cancer](https://onco.cc/cancers/her2-amplified-colorectal/), [KRAS G12C-mutant colorectal cancer](https://onco.cc/cancers/kras-g12c-colorectal/), [Lynch syndrome-associated colorectal cancer](https://onco.cc/cancers/lynch-associated-colorectal-cancer/), [Mismatch-repair deficient (MSI-high) colorectal cancer](https://onco.cc/cancers/msi-high-colorectal/), [Rectal cancer](https://onco.cc/cancers/rectal-cancer/), [Signet ring cell carcinoma of the colon and rectum](https://onco.cc/cancers/colorectal-signet-ring-cell-carcinoma/)
- technologies: [AI polyp detection in colonoscopy](https://onco.cc/technologies/ai-endoscopy-detection/), [Colorectal cancer screening (colonoscopy, FIT, stool DNA, blood)](https://onco.cc/technologies/colorectal-screening/), [Exercise & lifestyle oncology](https://onco.cc/technologies/exercise-oncology/), [Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- targets: [BRAF](https://onco.cc/targets/braf/), [HER2](https://onco.cc/targets/her2/), [KRAS](https://onco.cc/targets/kras/), [PD-1](https://onco.cc/targets/pd1/)
- drugs: [Bevacizumab](https://onco.cc/drugs/bevacizumab/), [CAPOX (capecitabine, oxaliplatin)](https://onco.cc/drugs/capox/), [Cetuximab](https://onco.cc/drugs/cetuximab/), [Cologuard](https://onco.cc/drugs/cologuard/), [Encorafenib](https://onco.cc/drugs/encorafenib/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Shield](https://onco.cc/drugs/shield/), [Sotorasib](https://onco.cc/drugs/sotorasib/), [Tucatinib](https://onco.cc/drugs/tucatinib/)
- pathways: [Colorectal cancer (KEGG map)](https://onco.cc/pathways/colorectal-cancer-signalling/)
- terms: [Colibactin](https://onco.cc/terms/colibactin/), [Colonoscopy](https://onco.cc/terms/colonoscopy/), [Faecal immunochemical test (FIT)](https://onco.cc/terms/fit-test/), [Lynch syndrome](https://onco.cc/terms/lynch-syndrome/), [Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)](https://onco.cc/terms/msi/), [NHS bowel cancer screening programme](https://onco.cc/terms/bowel-cancer-screening-uk/), [Organ preservation (watch-and-wait, bladder-sparing, larynx preservation)](https://onco.cc/terms/organ-preservation/), [Screening uptake](https://onco.cc/terms/screening-uptake/), [Sidedness (left vs right colon)](https://onco.cc/terms/sidedness/), [Total neoadjuvant therapy (TNT, rectal cancer)](https://onco.cc/terms/total-neoadjuvant-therapy/)
- trials: [CHALLENGE (CCTG CO.21)](https://onco.cc/trials/challenge/), [ECLIPSE (Shield blood test)](https://onco.cc/trials/eclipse-shield/), [NordICC (Nordic-European Initiative on Colorectal Cancer)](https://onco.cc/trials/nordicc/), [RAPIDO](https://onco.cc/trials/rapido/)
- people: [Chadwick Boseman](https://onco.cc/people/chadwick-boseman/), [John Burn](https://onco.cc/people/john-burn/), [Michael Bretthauer](https://onco.cc/people/michael-bretthauer/)
- key papers: [Colorectal cancer incidence patterns in the United States, 1974-2013](https://onco.cc/key-papers/paper-siegel-colorectal-incidence-birth-cohort-jnci-2017/), [Colorectal cancer statistics, 2023](https://onco.cc/key-papers/paper-siegel-colorectal-cancer-statistics-ca-2023/), [Geographic and age variations in mutational processes in colorectal cancer](https://onco.cc/key-papers/paper-diaz-gay-colibactin-geographic-age-mutational-processes-nature-2025/), [Increasing incidence of colorectal cancer in young adults in Europe over the last 25 years](https://onco.cc/key-papers/paper-vuik-early-onset-colorectal-europe-gut-2019/), [Increasing incidence of early-onset colorectal cancer (review)](https://onco.cc/key-papers/paper-sinicrope-early-onset-crc-nejm-2022/), [Sugar-sweetened beverage intake in adulthood and adolescence and risk of early-onset colorectal cancer among women](https://onco.cc/key-papers/paper-hur-sugar-sweetened-beverages-early-onset-colorectal-gut-2021/), [The consensus molecular subtypes of colorectal cancer](https://onco.cc/key-papers/paper-cms-guinney-nat-med-2015/), [US Preventive Services Task Force recommendation: colorectal cancer screening from age 45](https://onco.cc/key-papers/paper-uspstf-crc-screening-45-jama-2021/)
- ideas: [Automatic germline testing for every cancer type where it changes care](https://onco.cc/ideas/idea-prev-reflex-germline-testing/), [Find out what is driving early-onset bowel cancer, starting with colibactin, before extending screening any further](https://onco.cc/ideas/idea-crc-early-onset-cause-hunt/), [Offer the blood test for bowel cancer only to people who refuse stool tests or colonoscopy](https://onco.cc/ideas/idea-prev-blood-crc-test-for-non-responders/), [Treat screening uptake, not test sensitivity, as the thing to optimise, and settle the age extension with a trial rather than a model](https://onco.cc/ideas/idea-crc-screening-uptake-and-age-extension/), [UK gap: shorten the route to diagnosis for patients below the screening age, where the rise in incidence is](https://onco.cc/ideas/idea-crc-uk-young-patient-referral-and-diagnostic-interval/), [Use a polygenic risk score to set when screening starts](https://onco.cc/ideas/idea-prev-prs-screening-start-age/)
- institutions: [Bowel Cancer UK](https://onco.cc/institutions/bowel-cancer-uk/)
- roadmaps: [Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation](https://onco.cc/roadmaps/colorectal-roadmap/)

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JSON: https://onco.cc/api/v1/entities/early-onset-colorectal.json