Stomach cancer (gastric carcinoma):
warning signs, treatment & eating without a (full) stomach

1. What is stomach cancer?

Stomach cancer is a malignant tumour of the stomach lining. In the vast majority of cases it is an adenocarcinoma, meaning a cancer that arises from the glandular cells of the lining. The guideline also includes tumours at the junction between the oesophagus and the stomach, because they are treated in a similar way.^¹ Rarer stomach tumours such as lymphomas, gastrointestinal stromal tumours (GIST) or neuroendocrine tumours are separate diseases with different treatment.

In Germany, around 14,600 people are newly diagnosed with stomach cancer each year, men considerably more often than women; the average age at diagnosis is in the early 70s. Incidence and death rates have been falling for decades — mainly because Helicobacter infections have become less common and food today is refrigerated rather than cured and salted.^²

The problem: stomach cancer barely makes itself felt for a long time, and its first symptoms resemble those of harmless stomach problems. Most people with pressure in the upper abdomen, a feeling of fullness or stomach pain have gastritis or functional dyspepsia — not cancer. This article focuses on when symptoms are a warning sign, how stomach cancer is treated and how life works after stomach surgery.

2. Types, stages and tumour biology

Doctors describe stomach cancer by several features that together determine treatment:^¹,³

• Laurén growth type: the intestinal type forms well-defined tumours and often develops on the basis of long-standing inflammation of the lining. The diffuse type spreads across the stomach wall, also occurs in younger people and is harder to delineate.
• Location: tumours in the lower stomach, in the body of the stomach, or at the stomach entrance or junction with the oesophagus. The location helps decide whether part or all of the stomach has to be removed.
• Early gastric cancer: the tumour is confined to the upper layers of the wall. Some early cancers can be removed completely during a gastroscopy.
• Stage: the TNM system describes how deeply the tumour has grown into the stomach wall, whether lymph nodes are affected and whether there are metastases, for example in the lining of the abdomen (peritoneum) or in the liver.

Tumour biology: important for choosing medicines

Today, tumour tissue is tested for certain features: the protein HER2, so-called microsatellite instability (MSI), the PD-L1 score and the surface protein claudin 18.2. Depending on the result, different antibodies may be considered. This testing belongs before the treatment decision, especially at an advanced stage.^¹

3. Symptoms: when stomach complaints are a warning sign

In the early stage, stomach cancer usually causes no symptoms or only non-specific ones. Later, the following signs can appear — the so-called red-flag symptoms are particularly important:^¹,³

• Non-specific: pressure or pain in the upper abdomen, feeling full early, loss of appetite, nausea, belching.
• Red flag difficulty swallowing: food gets stuck — typical of tumours at the stomach entrance.
• Red flag weight loss: unintentional and marked, often together with a drop in energy.
• Red flag vomiting: repeated, especially when the stomach outlet is narrowed.
• Red flag bleeding: black, tarry stools, vomiting blood or vomit that looks like coffee grounds.
• Red flag anaemia: tiredness, paleness and breathlessness on exertion due to iron deficiency anaemia with no apparent cause.

4. Causes and risk factors

• Helicobacter pylori: this stomach bacterium is the most important risk factor. An infection lasting decades can lead to cancer via chronic inflammation and changes to the lining. Treating the infection lowers the risk — which is why the guidelines recommend, among other things, that first-degree relatives of people with stomach cancer are tested for the bacterium and treated if it is found. More in the article Helicobacter pylori.^²,⁴
• Lifestyle: smoking, alcohol, very salty, cured or smoked food and a lot of processed meat increase the risk.^²
• Reflux: long-standing heartburn increases the risk of tumours at the junction with the oesophagus.^²
• Pre-existing conditions: autoimmune gastritis (often linked to vitamin B12 deficiency), certain types of stomach polyps and previous stomach surgery.
• Family and genes: in first-degree relatives the risk is roughly two to three times higher. Rare hereditary syndromes such as hereditary diffuse gastric cancer or Lynch syndrome, which also raises the risk of bowel cancer, carry a very high risk.^²
• Epstein-Barr virus: plays a role in a small proportion of stomach cancers.^²

5. Diagnosis: from gastroscopy to treatment plan

The decisive step is a gastroscopy with tissue samples. Only this can reliably confirm or rule out stomach cancer. Staging tests to check how far it has spread follow afterwards.^¹

• Gastroscopy with biopsies: several tissue samples from all suspicious areas; these are also tested for Helicobacter.
• Endoscopic ultrasound: shows how deep the tumour reaches into the stomach wall and whether nearby lymph nodes are enlarged.
• CT of the chest and abdomen: looks for metastases, for example in the liver, lungs or lymph nodes.
• Laparoscopy (keyhole examination of the abdomen): for advanced tumours, to detect spread to the peritoneum that CT often misses.
• Tumour biology: HER2, MSI, PD-L1 and claudin 18.2 in the tissue.
• Nutritional status and general condition: weight loss and muscle loss affect tolerability and prognosis and are treated early.
• Tumour board: specialists in gastroenterology, surgery, oncology, radiotherapy, radiology and pathology agree on the recommendation together.

Tumour markers in the blood are not suitable for detecting or ruling out stomach cancer. Treatment should be planned at an experienced centre, such as a certified stomach cancer centre. Good preparation helps for the consultation — see Preparing for a doctor's appointment.

6. Treatment by stage

Treatment depends on the stage, location, tumour biology and general condition. It is planned at the tumour board; you make the decision together with your treatment team. A cure is possible above all at early and locally confined stages — but effective treatments exist beyond that too.^¹

7. Medicines in stomach cancer treatment

On top of the cancer treatment come medicines for nausea, diarrhoea or pain, supplements and your existing long-term medication. Some combinations are real pitfalls.^⁵

Fluorouracil and capecitabine: three important rules

• DPD test before starting: the enzyme dihydropyrimidine dehydrogenase breaks down fluorouracil and capecitabine. People who have too little of it can develop severe to life-threatening side effects. According to the Summary of Product Characteristics, a DPD deficiency test should therefore be carried out before treatment begins.^⁵
• No brivudine: the shingles medicine brivudine must not be taken together with fluorouracil or capecitabine — nor in the weeks before. The combination can be fatal. If you develop shingles during treatment, tell every practice and pharmacy that you are receiving a fluoropyrimidine.^⁵
• Blood thinners: capecitabine can markedly increase the effect of coumarins such as phenprocoumon. The INR then has to be monitored more closely.^⁵

Typical side effects of chemotherapy

Oxaliplatin frequently causes tingling and abnormal sensations in the hands, feet and mouth that are triggered or worsened by cold — in the days after the infusion, wear gloves when reaching into the fridge and avoid ice-cold drinks. Docetaxel can sharply lower blood counts. Fluoropyrimidines cause diarrhoea and sore mucous membranes, and capecitabine also causes hand-foot syndrome, with red, painful skin on the palms and soles.^⁵,⁶ Nausea can be prevented effectively, for example with ondansetron; it works best when taken exactly to schedule — not only once you already feel sick.^⁶

Immunotherapy and antibodies

Checkpoint inhibitors can trigger inflammation in healthy organs, for example in the bowel, liver, lungs, skin or thyroid — even months after starting. With zolbetuximab, nausea and vomiting during the infusion are common, which is why anti-sickness medicines are given preventively. Trastuzumab can impair heart function; this is therefore checked regularly.^¹

8. Eating without a (full) stomach

After a gastrectomy, the reservoir that portions food, acidifies it and releases it slowly into the intestine is gone. Even after partial removal, the stomach is considerably smaller. The body adapts — but this often takes months, and unintentional weight loss is common during this time. Nutritional counselling is therefore an integral part of treatment, ideally starting before surgery.^¹,³

• Many small meals — six to eight spread over the day instead of three large ones.
• Eat slowly, chew thoroughly — the mouth takes over part of the work the stomach used to do.
• Separate drinking and eating — have larger amounts of fluid between meals rather than with them, so that the food does not slip into the intestine too quickly.
• Sugar in moderation, protein at every meal — sweets and sugary drinks easily trigger dumping; protein helps prevent muscle loss.
• Test what you tolerate — some people tolerate dairy products less well after surgery than before, see lactose intolerance; a food diary helps you find out.

Recognising dumping syndrome

For most people, dumping symptoms improve over time and with an adapted diet. If they persist, the practice can look into further measures.^³

9. Tablets and nutrients after stomach surgery

Without a stomach, or with only a small remnant, what the body can absorb from food — and in some cases from tablets — changes. The most important points:^¹,³

• Lifelong vitamin B12: to absorb vitamin B12, the intestine needs a helper substance from the stomach lining called intrinsic factor. After a gastrectomy it is missing; without replacement, a deficiency with anaemia and nerve damage develops over months to years. B12 is therefore replaced for life, usually as injections at regular intervals. Whether high-dose tablets are enough is decided by the practice based on blood tests. More under vitamin B12 deficiency.
• Iron: without stomach acid, and because the duodenum is often bypassed, iron absorption falls. If there is a deficiency, iron supplements or iron infusions may be considered.
• Calcium and vitamin D: their absorption can also fall; in the long term the risk of osteoporosis rises. Blood levels and, if necessary, bone density are monitored.
• Fatty stools: if digestive enzymes from the pancreas no longer mix properly with food, fatty, foul-smelling stools can result. Enzyme capsules taken with meals can then help.
• Review acid blockers: after complete removal of the stomach, no more stomach acid is produced. The practice should check whether a proton pump inhibitor is still needed; reflux of bile can hardly be influenced by it anyway.
• Large tablets and modified-release forms: swallowing problems at the join can occur. Before splitting or crushing, ask whether this is allowed for the particular product — tips in the guide How to swallow tablets.
• Set up your medication plan again: a lot has often changed after surgery — weight, blood pressure, blood sugar. Have all your long-term medication reviewed, see Reviewing long-term medication.

10. Follow-up care and everyday life

Treatment aimed at a cure is followed by structured follow-up care. It is guided by symptoms, nutritional status and deficiencies; after endoscopic removal, regular follow-up gastroscopies are added.^¹

• Weigh yourself regularly — once a week, always at the same time. Further weight loss is a reason to talk to your practice and nutritional counsellor early.
• Make use of rehabilitation — a rehabilitation programme directly after treatment (Anschlussheilbehandlung), with nutrition training and exercise, helps you regain strength and routine.
• Inform your family — first-degree relatives should be tested for Helicobacter pylori; if the person affected is very young or there are several cases in the family, genetic counselling may be worthwhile.^⁴
• Agree on supplements — not everything helps, and some things interfere with treatment. Whatever you take as a supplement belongs on your medication plan, see Supplements and medications.
• Stay smoke-free and keep alcohol low — without a stomach, alcohol acts faster and more strongly because it reaches the intestine unchecked.
• Emotional support — psycho-oncology services and cancer counselling centres help with fear of recurrence and with questions about work, pension and the severe disability pass (Schwerbehindertenausweis).

Keeping a complete overview of all medicines, supplements and injection dates is even more important after stomach surgery than before. How to do this is explained in the guide Creating a medication plan.

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