Side effects of radiation therapy for stomach cancer

Side effects can happen with any type of treatment for stomach cancer, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. Damage to these healthy cells may cause side effects. Side effects can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of radiation therapy will depend mainly on:

  • the size of the area being treated
  • the specific area or organs being treated
  • the total dose
  • the treatment schedule
  • whether or not chemotherapy is being given at the same time as radiation therapy (called chemoradiation)

Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Skin reactions

Skin reactions happen because external beam radiation has to travel through the skin to reach the area being targeted for treatment. The skin in the radiated area may become red or dry or change colour (become darker or tanned looking). Most skin reactions occur within the first 2 weeks of receiving radiation treatment. They usually go away a few weeks after treatment, but some skin changes, like skin darkening or scarring, can stay for a long time. Some people don’t have any skin reactions with radiation therapy.

Find out more about skin problems.

Nausea and vomiting

Nausea and vomiting are common with stomach cancer because a large area of the upper abdomen is treated with radiation. Nausea and vomiting happen more often when chemotherapy is also used (called chemoradiation). About 1–2 weeks into therapy, you may start to feel nauseated about 1–3 hours after your daily treatment. Some people find that eating a small snack before treatment helps prevent nausea and vomiting. Others do not eat for a few hours before treatment or wait a few hours after treatment before eating again.

Tell your radiation therapy team if you have nausea and vomiting. This side effect can usually be managed with medicine. Nausea and vomiting usually go away after treatment is finished.

Radiation enteritis and diarrhea

Radiation therapy for stomach cancer may include the lower abdomen. This can irritate the bowels (intestines), especially the small intestine, and cause radiation enteritis.

Symptoms of radiation enteritis include abdominal cramping and diarrhea, which may start about 2–3 weeks into radiation therapy. Report cramping and diarrhea to the radiation therapy team. Your doctor may prescribe medicine to help manage diarrhea.

Find out more about radiation enteritis and diarrhea.


Fatigue is a general lack of energy, tiredness or exhaustion. It’s one of the most common side effects of radiation therapy. Fatigue may be caused by anemia, poor appetite or depression. It may also be related to toxic substances that are produced when cancer cells break down and die. During radiation therapy, the body uses more energy to heal itself, so even if you rest, you might still feel tired.

Fatigue usually occurs during or after the second week of radiation therapy. Symptoms of fatigue may increase or become more severe over the course of treatment. Fatigue usually goes away gradually after treatment has ended, but some people continue to feel tired for several weeks or months after radiation therapy.

Find out more about fatigue and anemia.

Low blood cell counts

Low blood cell counts (caused by bone marrow suppression) can happen during radiation therapy.

  • A low platelet count (thrombocytopenia) increases the risk of bruising and bleeding.
  • A low red blood cell count (anemia) causes fatigue, paleness and malaise.
  • A low white blood cell count (neutropenia) increases the risk of infection. Radiation therapy most often affects white blood cells when there is blood loss.

Low blood cell counts occur because of radiation's effect on the bone marrow. Blood cell counts are most often affected in people who are having chemotherapy during the same period as radiation therapy. Blood cell counts return to normal after treatment has ended.

Find out more about bone marrow suppression.

Weight loss

Losing weight is a concern for most people with stomach cancer and it is a common side effect of radiation therapy. Radiation therapy can cause nausea and vomiting and a loss of appetite. This can lead to weight loss during treatment.

It is important to maintain your weight even if your appetite has changed. Proper nutrition helps the body fight disease and cope with the effects of cancer treatment. If a person with stomach cancer can’t maintain their weight through diet, the healthcare team may suggest nutritional supplements or a feeding tube.

Hair loss

Hair loss (alopecia) only occurs in the area being treated. Thinning or loss of hair can occur in any area where radiation has been directed. The extent of hair loss and regrowth varies from person to person and depends on the dose of radiation.

Hair loss can begin 2–3 weeks after radiation therapy starts. Smaller doses of radiation usually result in temporary hair loss, but permanent hair loss is more common at higher doses. When hair regrows, usually about 3–6 months after radiation treatment is finished, the colour or texture may be different and it may grow back thinner or patchy.

Heart and lung damage

Radiation therapy for stomach cancer may damage the heart and lungs since they are so close to the area being treated. Special shields are made to protect the heart and lungs and other organs in the area as much as possible.

Tell the healthcare team if you have shortness of breath, chest pain, cough or swelling of the arms or legs as these may be signs of heart or lung damage.

Kidney damage

Part of one kidney may be in the area being treated by radiation therapy for stomach cancer. In rare situations, the radiation may damage that kidney. This is not usually a problem for people who have 2 healthy kidneys before starting radiation. A person can live a normal, healthy life with one working kidney or even part of a kidney.

Second cancers

A very small number of people develop a second cancer caused by radiation therapy. The benefit of treating cancer usually far outweighs the risk of developing a second cancer from radiation therapy. People who receive both chemotherapy and radiation therapy have the highest risk of developing a second cancer. A second cancer can develop a few years after radiation treatment, but most do not occur for 10–20 years or more after treatment.

Expert review and references

  • American Society of Clinical Oncology (ASCO). Stomach cancer. Alexandria, VA.: American Society of Clinical Oncology (ASCO); 2014.
  • Avital, I. et al . Cancer of the stomach. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles & Practice of Oncology. 9th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011: 80: pp. 924-954.
  • Cancer Research UK. Stomach cancer. Reviewed ed. Cancer Research UK; 2014.
  • Czito BG, Palta M & Willett CG . Stomach cancer. Halperin EC, Wazer DE, Perez CA et al. Perez and Brady's Principles and Practice of Radiation Oncology. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013: 58.
  • National Comprehensive Cancer Network. Gastric Cancer (Version 1.2014). National Comprehensive Cancer Network; 2014.