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EORTC 22921: What the Colorectal Cancer Trial Found
EORTC 22921 tested chemoradiation timing in rectal cancer in colorectal cancer, measuring local control. Plain-language summary of a positive result on its main measure — and what it doesn't mean.
Original commentary from the Cancer Explained editorial team.
Historical context: this page explains an event dated 2006. It was published as an explainer on July 12, 2026 and is not breaking news.
Please note: this page is educational only — it is not medical advice, and it does not speculate about anyone’s health beyond reliable public reporting. For questions about your own health, talk with your healthcare team.
Why the rectum is a harder place to operate
Colon and rectal cancer get grouped together. Surgically they are not the same problem.
The colon sits loose in the abdomen with room around it. The rectum is the last stretch of bowel, packed into the bony pelvis beside the bladder, the sexual organs and the nerves that control them. There is very little margin.
That narrow space gives rectal cancer a distinct failure mode. Even after a good operation, cancer can return in the pelvis itself. Recurrence there is hard to remove a second time and hard to live with.
Radiotherapy before surgery was already established for that reason. EORTC 22921 asked a different question: does adding chemotherapy help, and does it matter when you give it?
A four-way split
The trial enrolled 1,011 patients with clinical stage T3 or T4 rectal cancer that a surgeon could still remove. T3 means the tumor has grown through the muscle wall of the rectum; T4 means it has reached nearby structures.
Everyone got radiotherapy before surgery: 45 gray delivered over five weeks. Gray is the unit of absorbed radiation dose.
From there patients were split four ways.
- Radiotherapy before surgery, nothing added.
- Chemoradiotherapy before surgery.
- Radiotherapy before surgery, then chemotherapy after.
- Chemoradiotherapy before surgery, then chemotherapy after.
One chemotherapy course was fluorouracil at 350 milligrams per square meter a day. Leucovorin was added at 20 milligrams per square meter a day. Both ran for five days. Two courses went with the radiotherapy. Four more were planned after surgery in the arms that called for it.
The stated primary endpoint was overall survival.
On survival, the answer was no
Survival did not differ between the groups given chemotherapy before surgery and those given it after. The p-values were 0.84 and 0.12. Five-year overall survival across all four arms combined was 65.2 percent.
By its own main measure the trial was negative. Adding chemotherapy to radiotherapy did not make people live longer, in any order.
On local control, the answer was a halving
The secondary result is the one that stuck.
Five-year local recurrence ran 8.7 percent for chemotherapy before surgery, 9.6 percent for chemotherapy after, and 7.6 percent when both were given. In the arm with radiotherapy alone and no chemotherapy at all, it was 17.1 percent. The p-value was 0.002.
Roughly half the pelvic recurrences disappeared. Nobody lived longer for it. Fewer people faced a cancer growing back in the pelvis. Our page on colorectal cancer treatment covers what that means in practice.
The number that changed the schedule
Buried in the results is a figure about human beings rather than tumors.
Adherence to preoperative chemotherapy was 82.0 percent. Adherence to postoperative chemotherapy was 42.9 percent.
Fewer than half of the people assigned chemotherapy after surgery actually completed it. That is not a surprise once you picture the sequence: major pelvic surgery, a possible stoma, weeks of recovery, then an offer of more chemotherapy.
Before surgery, patients are stronger. That gap did as much as any efficacy result to move treatment ahead of the operation.
Where rectal treatment stands now
NCI's health-professional summary calls preoperative chemoradiation the standard of care for stage T3 to T4 or node-positive rectal cancer. It cites the German Rectal Cancer Study Group trial and NSABP R-03 among others.
The benefits NCI lists are shrinking the tumor, lowering the stage, and making a complete removal easier. It also lists better local control, a better toxicity profile, and a higher rate of keeping the anal sphincter. Tumor disappears completely from the surgical specimen in 10 to 25 percent of cases.
Total neoadjuvant therapy moves all the chemotherapy in front of surgery too. NCI lists that as an option now.
When to get checked
Rectal cancer usually announces itself through the bowel. NCI lists these signs, and notes that other conditions cause them too.
- Blood in the stool, bright red or very dark.
- A change in bowel habits.
- Diarrhea, or constipation.
- A feeling the bowel does not empty.
- Stools narrower than usual.
- Gas pains, bloating, fullness or cramps.
- Weight loss with no known cause.
- Fatigue.
- Vomiting.
The firm thresholds come from screening. The US Preventive Services Task Force gives colorectal screening a grade A for all adults aged 50 to 75. For adults aged 45 to 49 it is a grade B. From 76 to 85 the advice is to screen some people and not others, based on health and past tests.
Visible rectal bleeding is worth a same-week appointment at any age. Piles are the usual cause. They are not the only one. Our page on colorectal cancer symptoms sets out what else can sit behind each sign.
The population numbers
The American Cancer Society projects 158,850 new US colorectal cancer cases and 55,230 deaths for 2026, the pair of estimates SEER reprints; NCI's own SEER data put the median age at diagnosis at 66. Colorectal cancer is the second leading cause of cancer death in the United States.
Five-year relative survival for cases diagnosed from 2016 to 2022 is 65.4 percent overall: 91.3 percent for localized disease, 75.2 percent when regional nodes are involved, and 16.9 percent for distant spread.
These averages cover colon and rectal cancer together, across every treatment used in that window. They describe a population, not a person.
What this trial cannot tell you
The surgery was not standardized. Total mesorectal excision means taking out the rectum inside its intact fatty envelope. It was not required at every center. Surgical quality is one of the strongest drivers of local recurrence, so part of the gap may sit in the operating room rather than the drug.
Splitting 1,011 patients four ways leaves small groups. That limits the power to detect a survival difference even if one exists.
The chemotherapy is dated. Fluorouracil with leucovorin was standard in the 1990s. It is not what a modern regimen looks like.
And halved local recurrence without a survival gain is a trade, not a win. The trial cannot tell you how one person should weigh it.
Sources
- Bosset JF and others, Chemotherapy with Preoperative Radiotherapy in Rectal Cancer, New England Journal of Medicine 2006 (record and abstract via NCBI) — https://pubmed.ncbi.nlm.nih.gov/16971718/
- NCI PDQ, Rectal Cancer Treatment (Health Professional Version) — https://www.cancer.gov/types/colorectal/hp/rectal-treatment-pdq
- NCI PDQ, Colon Cancer Treatment (Patient Version) — https://www.cancer.gov/types/colorectal/patient/colon-treatment-pdq
- US Preventive Services Task Force, Colorectal Cancer: Screening — https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening
- SEER Cancer Stat Facts, Colorectal Cancer — https://seer.cancer.gov/statfacts/html/colorect.html
How this article was prepared
An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.
The National Cancer Information Foundation publishes Cancer Explained. This page is for learning. It is not medical advice and does not suggest a test or treatment.
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Put the story in context
Prevention, possible warning signs, screening, and diagnosis
This story relates to Colorectal cancer. The information below is general: it does not reveal anything else about a public person’s health, and not every point applies to every cancer. Personal advice depends on age, symptoms, family history, exposures, and medical history.
Prevention and risk reduction
Not every cancer can be prevented. Avoiding tobacco, protecting skin from ultraviolet radiation, limiting alcohol, staying active, and receiving recommended HPV or hepatitis B vaccination can lower the risk of certain cancers. A risk factor is not a prediction or a cause in one individual.
Symptoms and possible early signs
Possible signs vary and are often caused by conditions other than cancer. Changes worth discussing include a new lump, unexplained bleeding or weight loss, a persistent cough, lasting bowel or bladder changes, a changing skin spot, or symptoms that persist or worsen. Some early cancers cause no symptoms.
Screening and early detection
Screening looks for certain cancers before symptoms begin. Recommended tests exist only for some cancers and depend on age and risk. Screening can have benefits and harms; it is not the same as evaluating a new symptom, and there is no single routine scan or blood test that reliably screens for every cancer.
How cancer is diagnosed
Diagnosis may involve a history and exam, imaging, laboratory tests, and often a biopsy. Pathology can identify the cancer type and may test biomarkers that guide treatment. Symptoms, screening results, tumor markers, or online stories alone cannot confirm cancer.
Learn about this story’s cancer topic
A public story may encourage questions, but it should not be used to estimate your risk or choose testing. Contact a healthcare professional about a persistent or concerning change. Seek urgent care for severe or rapidly worsening symptoms.