Bowel cancer (colorectal cancer) is a malignant tumour in the large bowel (colon) or the back passage (rectum). It is one of the most common cancers in Germany — and at the same time one of the easiest to prevent.¹
The reason lies in how it comes about: the great majority of bowel tumours develop over many years out of initially benign growths in the lining of the bowel, the polyps (adenomas). That long window is the great opportunity of screening: anyone who has polyps removed during a colonoscopy prevents the cancer before it ever arises.
The most important message in this article. In its early stages bowel cancer usually causes no symptoms at all. Waiting for symptoms means giving away the decisive head start — screening from the age of 50 is therefore not a formality but the single most effective measure against this disease. How to keep your bowel healthy day to day is covered in the guide Gut health.
2. Screening: stool test and colonoscopy
The statutory screening programme offers two routes — and for people with statutory health insurance both are covered from the age of 50:²,³
The stool test (iFOBT)
The immunochemical faecal occult blood test detects the tiniest, invisible traces of blood of the kind that polyps or tumours can produce. You collect the test kit at the practice, take a sample at home and return it for laboratory analysis. The test is usually offered annually from the age of 50 and every two years from 55 — provided you do not take up the offer of a colonoscopy. One point matters: a positive stool test does not mean cancer, only that blood has been found — a colonoscopy then establishes the cause. Conversely, an unremarkable test does not reliably rule a tumour out; what counts is repeating it at the set intervals.
The colonoscopy
Colonoscopy is the most thorough examination there is: the whole of the large bowel is inspected with a camera, and polyps are removed there and then during the same procedure. People with statutory health insurance are entitled to two screening colonoscopies at least ten years apart — men from the age of 50, women under the arrangements so far from 55; the age limits have been adjusted more recently, and your practice or health insurer can tell you where things currently stand.³ The insurers write to everyone who is entitled, inviting them to take part.
The examination usually takes 20 to 30 minutes and is carried out with brief sedation if you wish — most people are not aware of any of it. The most unpleasant part is clearing the bowel the day before. If nothing untoward is found, no further screening colonoscopy is needed for about ten years.
Earlier screening if bowel cancer runs in the family. If a parent or a sibling has had bowel cancer or advanced polyps, screening starts considerably earlier — as a rule of thumb about ten years before the age at which your relative was diagnosed. Raise it yourself — the guide Preparing for a doctor’s appointment helps with that conversation.
3. Symptoms and warning signs
In its early stages bowel cancer usually causes no symptoms — that is what makes it so treacherous. Warning signs that need looking into:
Blood in your stool — visibly red, mixed in dark, or as black stool. Haemorrhoids are often behind it — but only an examination may decide that, never an assumption.
Changed bowel habits — newly appearing constipation, diarrhoea or an alternation between the two over several weeks; also pencil-thin stools.
Unintended weight loss and a drop in performance with no obvious reason.
Persistent abdominal pain or cramps — above all when they are new and keep coming back.
Anaemia from chronic blood loss — an unexplained iron deficiency anaemia in someone over 50 is always a reason to examine the bowel.
Never sit a warning sign out. None of these symptoms proves cancer — most have harmless causes. But every one of them deserves to be looked into if it is new and lasts longer than two to three weeks — at any age.
4. Causes and risk factors
Bowel cancer arises from the interplay of predisposition, age and lifestyle. The most important risk factors:¹
Age — the risk rises markedly from around 50. At the same time more cases are being seen worldwide in younger people — which is why warning signs count at any age.
Family history — bowel cancer or advanced polyps in a first-degree relative raises your own risk considerably.
Inherited syndromes — rare but important: Lynch syndrome (HNPCC) and familial adenomatous polyposis (FAP) cause disease at a young age and call for surveillance programmes of their own.
Inflammatory bowel disease — long-standing ulcerative colitis, and in part also Crohn’s disease, raise the risk — with their own screening intervals.
Lifestyle — smoking, regular alcohol, marked obesity, too little exercise and a high intake of red and processed meat are all considered to raise the risk; fibre and physical activity are considered protective.
Type 2 diabetes — statistically goes along with a raised risk of bowel cancer.
5. Diagnosis and stages
Once there is a suspicion, the work-up follows clear steps:
Colonoscopy with a tissue sample: The standard. Only examination of the tissue under the microscope (biopsy) confirms the diagnosis.
Imaging: Ultrasound, a CT scan of the abdomen and chest — for rectal cancer an MRI scan of the pelvis as well — to establish how far the tumour extends and whether it has spread.
Blood tests: A full blood count and the tumour marker CEA as a baseline for monitoring over time — the background is in the guide Understanding your blood values.
Molecular testing of the tumour: In advanced disease the tissue is tested for features such as RAS and BRAF mutations or microsatellite instability (MSI) — which targeted medicines are an option depends on the result.
These findings together give the stage — put simply: how deeply has the tumour grown into the bowel wall, are lymph nodes involved, has it spread to other organs (metastases)? The stage determines the treatment:
Stage (simplified)
What that means
Typical treatment
Stage 0
The earliest form, confined to the topmost layer of the lining
Removal during the colonoscopy — often that is all that is needed
Stage I
Tumour limited to the inner layers of the wall, no lymph nodes involved
Surgery; chemotherapy is usually not needed
Stage II
Tumour grows through the bowel wall, lymph nodes clear
Surgery; supportive chemotherapy only in certain higher-risk situations
Stage III
Lymph nodes in the surrounding area are involved
Surgery plus supportive (adjuvant) chemotherapy as a rule
Stage IV
Spread to other organs, for example the liver or the lungs
An individual combination of medicines, surgery and local procedures
Table scrolls to the right
The earlier the stage, the better the outlook — and even in stage IV there are courses today with a prospect of cure, for instance with single, operable liver metastases. Blanket percentages help little in an individual case; only your treatment team can put your prognosis in context on the basis of your findings.¹
Treatment is planned case by case at a tumour board — where surgery, oncology, radiotherapy, radiology and pathology all sit around one table. What follows is therefore a guide to the building blocks, not a treatment plan: which combination is right for you is settled by the treatment team together with you.¹
MainstaySurgery — the basis of almost every cure
Removing the affected section
The affected stretch of bowel is removed together with the lymph nodes belonging to it, often by keyhole surgery. In most cases the two ends of the bowel are then joined back together straight away.
Rectal cancer: treatment beforehand
With cancer of the rectum, surgery is preceded — depending on how far the tumour extends — by radiotherapy or chemoradiotherapy, to shrink the tumour and lower the risk of it coming back in the pelvis.
MedicinesChemotherapy and targeted agents
Chemotherapy
The basis is usually a fluoropyrimidine (5-fluorouracil as an infusion or capecitabine as a tablet), often combined with oxaliplatin or irinotecan. Given after surgery in stage III it lowers the risk of recurrence (“adjuvant” treatment); with metastases it slows the tumour down. The regimen and its duration are set by the oncology team.
Targeted antibodies
Agents directed against growth signals (EGFR) or against the tumour’s new blood vessels (VEGF) are an option in advanced disease — but only if the molecular tests on the tumour fit. They add to chemotherapy and usually do not replace it.
Immunotherapy
In the subgroup with microsatellite instability (MSI-H), checkpoint inhibitors can work very well — this affects only a small proportion of patients and is identified through testing of the tumour.
Realistic expectations instead of promises of a cure. No medicine is guaranteed to “beat” bowel cancer — but the combination of surgery, modern systemic treatment and good follow-up care has noticeably improved the outlook over recent decades. A second opinion before major treatment decisions is your right, and in certified bowel cancer centres it is explicitly the norm.
7. Managing the side effects of chemotherapy
For many patients it is not the diagnosis but day-to-day life on chemotherapy that is the greatest burden. The good news: side effects can be headed off far better today than they used to be — with supportive medicines that are every bit as much part of the treatment as the chemotherapy itself.⁴
Many chemotherapies, above all in the first days of a cycle
Anti-sickness medicines to a fixed schedule — from setrons and steroids through to metoclopramide as an as-needed medicine. Taken pre-emptively they work better than “only once it gets bad”.
Keep your fluid intake up; loperamide as instructed by your team. Diarrhoea that persists or contains blood must be reported straight away.
Constipation
Supportive medicines such as setrons, and moving about less
Fibre, exercise, and macrogol if needed — matched to the surgery you have had and to the state of your bowel.
Tingling in the hands and feet
Oxaliplatin (polyneuropathy), often triggered by cold
Avoid cold on your hands and feet and in what you drink; report the tingling early — the dose can be adjusted before the nerves are damaged for good.
Hand-foot syndrome
Capecitabine, 5-FU
Rich moisturising care, avoiding pressure and friction; with painful redness, get advice — often a break in treatment or a dose adjustment is enough.
Exhaustion (fatigue)
Practically every phase of treatment
Paradoxical but well documented: moderate, regular exercise helps more than resting up. Persistent tiredness should also be checked for anaemia.
Table scrolls to the right
A fever during chemotherapy is an emergency. Chemotherapy can temporarily push your immune cells right down. A temperature of 38.3 °C or above (or repeatedly over 38 °C) during this phase can signal a serious infection and must be reported immediately — day or night, to the oncology day unit or the emergency department. Do not wait until morning and do not simply take something to bring the fever down.
During the chemotherapy phase in particular, five or more preparations quickly add up — the chemotherapy, anti-sickness medicines, painkillers, your long-term medication. To make sure nothing clashes and nothing is forgotten, an up-to-date overview is worth the effort: the guide Keeping a medication list shows how. Do also tell your treatment team about every new preparation — including herbal ones such as St John’s wort — because some of them affect how chemotherapy is broken down; the background is in the guides Drug interactions and Medication side effects.
Nausea, tingling, fever: keep a record of what the chemo does
Note down side effects and supportive medicines — ready for your next conversation with the oncology team.
8. Follow-up care: the plan for the years afterwards
Once treatment is finished, structured follow-up care begins — as a rule over five years. Its purpose: to pick up a recurrence or a second tumour early enough for it still to be treatable, and to deal with the after-effects of treatment. The German S3 guideline recommends regular checks above all for stages II and III, because that is where follow-up has been shown to help.¹ The usual building blocks:
Consultation and physical examination: at first usually every six months, later once a year — including a talk about symptoms, weight and digestion.
The tumour marker CEA: a blood value that can show a rising trend over time. Single readings say little — what counts is the trend.
Colonoscopy: as a rule about a year after the operation, and then at longer intervals if nothing untoward is found.
Imaging: ultrasound of the liver and, depending on the stage, CT checks; with rectal cancer, examinations of the rectum as well.
The exact intervals depend on the stage and on how things go — you will get your personal follow-up plan in writing from your treatment team or bowel cancer centre. What matters is that the appointments actually happen: it is precisely in the third and fourth year, once everyday life has taken over again, that gaps creep in. A calendar, reminders or an app help you keep to the rhythm.
9. Everyday life, diet and living with a stoma
Keep moving — on current evidence, regular moderate activity improves fatigue and quality of life, and probably the prognosis too. Brisk walking already counts.
Eat what your bowel tolerates — after bowel surgery digestion needs months to settle into a new rhythm. Several small meals, chewing well and a food diary help more than rigid lists of forbidden foods; dietary counselling is often available on statutory health insurance.
Accept support — post-treatment rehabilitation, psycho-oncology and support groups are not a weakness but part of the treatment. Tips for living with a long-term condition are in the guide Chronic illness in everyday life.
Use the entitlements you have — a recognised disability card, exemption from prescription charges and home help are open to many patients in Germany. The social services departments of the hospitals advise free of charge.
In brief: living with a stoma
An artificial opening of the bowel (a stoma) is the exception today, not the rule — and where one is needed it is often only temporary: in operations on the rectum a protective stoma is often created and then reversed after a few months. If it does have to stay permanently, a largely normal life is possible — with sport, travel and work. Stoma nurses teach you how to manage the appliance, and contact with others in the same position (for example through Deutsche ILCO, the German stoma association) is an enormous help, especially at the start.
Five years of follow-up appointments — without gaps
Reminders for check-ups and medicines, your history and your values in one place.
The statutory programme starts at 50: with the immunochemical stool test (iFOBT) and — depending on sex and on the arrangements currently in force — the screening colonoscopy, to which there is an entitlement twice, at least ten years apart. If bowel cancer runs in your family, the insurers cover the examination considerably earlier. Your practice or health insurer can tell you where things currently stand.
As a rule, no. Most people opt for brief sedation and sleep through the 20 to 30 minutes of the examination. The most unpleasant part is generally reckoned to be clearing the bowel with the prep solution the day before. After sedation you must not drive yourself that day.
No — most of the time more harmless causes such as haemorrhoids or an anal fissure are behind it. But that very assumption is the most dangerous trap: only an examination can establish whether it really is harmless. Blood in the stool therefore needs medical assessment at any age, and especially from 50 or if bowel cancer runs in your family.
That depends decisively on the stage. If the tumour is found early, the outlook is very good — many patients are cured for good. And even in advanced disease there are far more treatment options today than there used to be. Blanket percentages help little in an individual case; only your treatment team can judge your personal prognosis from your findings.
Modern anti-sickness medicines, taken pre-emptively to a fixed schedule — not only once the nausea is there. They include setrons, steroids and as-needed medicines such as metoclopramide. If you still suffer from nausea, say so to your treatment team: the schedule can almost always be adjusted. Small meals and enough to drink help on top of that.
As a rule five years to a fixed plan: regular consultations with a physical examination, the blood value CEA, a colonoscopy about a year after the operation, plus ultrasound and, depending on the stage, CT checks. The exact intervals depend on the stage and on how things go, and they are set out in your personal follow-up plan.
Often not. With operations on the rectum in particular, only a temporary protective stoma is usually created, and it is reversed after a few months. Whether a stoma is needed, and for how long, depends on where the tumour sits and how far it extends. Even with a permanent stoma a largely normal life is possible, with sport, travel and work.
In part, yes. The most effective step is the screening colonoscopy, because precancerous changes are removed during it. On top of that, not smoking, little alcohol, a normal weight, regular exercise and a fibre-rich diet with little red and processed meat lower the risk on current evidence. Complete protection, though, does not exist.
German S3 guideline on colorectal cancer (German Guideline Programme in Oncology: German Cancer Society, German Cancer Aid, AWMF reg. no. 021-007OL) — German source. awmf.org
gesundheitsinformation.de, German Institute for Quality and Efficiency in Health Care (IQWiG): Bowel cancer and bowel cancer screening — German source. Accessed 2026. gesundheitsinformation.de
gesund.bund.de: Bowel cancer — early detection and screening (directive of the Federal Joint Committee, G-BA) — German source. Accessed 2026. gesund.bund.de
German Cancer Information Service of the German Cancer Research Centre (DKFZ): Bowel cancer — treatment, side effects, follow-up care — German source. Accessed 2026. krebsinformationsdienst.de
Treatment and follow-up under control — with brite
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Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or treatment. With blood in your stool, unexplained weight loss or persistently changed digestion, have the cause assessed promptly; a fever during chemotherapy is an emergency and must be reported immediately. The choice of medicine and its dose is always decided individually by the treating practice. Last updated: August 2026.
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