Side effects of proton radiation

Possible Side Effects

Some people experience side effects from radiotherapy, while others do not.

Radiotherapy affects not only the tumor but also, to some extent, nearby healthy tissue, which means there is always a risk of side effects. Individuals tolerate different amounts of radiation, so side effects will vary from person to person. Many people do not experience any side effects at all.

Side effects of radiotherapy are often divided into early (acute) and late effects. Early side effects usually appear after two to three weeks of treatment but can sometimes start sooner. These effects do not disappear immediately after the last treatment; they typically peak shortly after the end of therapy and then gradually diminish. Late side effects may not become apparent until several months or even years after treatment ends.

Early Side Effects

Temporary Skin Problems
During radiotherapy, the skin in the treated area may react like a severe sunburn. The most common reactions are redness, irritation, and itching. These symptoms usually improve within a few weeks after treatment ends, but the skin can remain sensitive or slightly discolored for some time. Areas with skin folds—such as the armpits and groin—are especially sensitive.

When washing the irradiated area, use lukewarm water and gently pat the skin dry. Avoid rubbing, and use only mild, unscented soap. Do not use strong perfumes, deodorants, or irritants. There are also creams and ointments available to soothe the skin; ask your nurse or doctor for recommendations.

Wearing loose-fitting clothing over the treatment area can provide comfort. Choose fabrics that absorb moisture and keep the skin dry, as moisture can increase irritation. Protect the area from sun and wind, and avoid shaving the treated skin. Hair in the treatment area often stops growing for a time.
Eating well can help your skin heal, as the body needs extra energy and nutrients during this time.

Tiredness
Feeling tired during treatment is common. For some people, it is mild; for others, it may affect daily activities. Fatigue usually improves a few weeks after treatment is completed. Physical activity may help, but it can also help to rest in short intervals throughout the day. Remember, tiredness may have other causes, such as low blood counts, poor nutrition, or difficulty sleeping. Speak to your doctor or nurse if you are concerned about your fatigue.

Nausea
Some patients experience nausea during radiotherapy. This can happen at different times, either early in the course of treatment or later. Effective medications are available to help if you develop nausea; do not hesitate to ask your care team for support.

Late Side Effects

Skin Changes
After radiotherapy, the skin in the treated area may feel slightly stiff and hard. Some patients develop small visible blood vessels on the skin’s surface. This effect is called fibrosis, which is the formation of scar-like tissue due to chronic radiation injury. If fibrosis causes significant symptoms, surgical treatments may be considered.

Pain
If the area treated with radiation contains many nerves, you may experience pain, tingling, or even muscle weakness in that region. For example, radiotherapy to the collarbone or nearby regions may sometimes result in nerve symptoms affecting the arm.

Sexuality
Cancer and its treatments often affect your body and how you perceive yourself. Feelings such as anxiety and depression during cancer treatment can influence sexual desire and intimacy. If you have a partner, talk openly about your feelings and needs. Honest conversations are important for maintaining closeness and reducing misunderstandings—especially if one partner feels rejected. Physical touch and closeness without sexual expectations can help strengthen your relationship and restore intimacy.

Radiotherapy to the Head

Radiation therapy can affect hair growth in the treatment area, causing hair to stop growing and fall out. This applies to scalp hair, eyebrows, eyelashes, and facial hair such as beards. Hair outside the treated area is not affected. Hair will usually start to grow back a few months after the end of treatment, but the timing and amount depend on the radiation dose and your individual situation. With higher doses of radiation, hair loss can be permanent in the treated area.

If you lose your hair, you may be entitled to a wig or false eyelashes—ask your contact nurse or treating physician about what support is available in your region.

Radiotherapy to the Abdomen and Pelvis

Early side effects

Radiation treatment for tumors in the abdominal and pelvic region can cause nausea and other digestive problems, such as diarrhea or abdominal discomfort. The risk of these side effects increases if a larger area is treated. If you experience these symptoms, effective medications are available to help manage nausea and other problems.

Radiation therapy that involves the bladder may cause symptoms such as frequent urination and a burning sensation when you urinate. There are also medicines your healthcare team can recommend to relieve these bladder symptoms.

Late Side Effects

A late side effect of pelvic or abdominal radiotherapy is that the bladder can be affected, resulting in problems such as incontinence or bladder irritation. The bowels can also be affected, leading to diarrhea, urgency, and sometimes pain or bleeding. These symptoms may appear months or even years after treatment and often require ongoing management.

If you experience bladder or bowel symptoms, a physiotherapist can help you strengthen your muscles and improve control. Effective medicines are also available to help relieve these symptoms. Patients in need may be eligible to receive free incontinence pads from their local nurse.

Women who receive pelvic or lower abdominal radiotherapy may have problems with fragile mucous membranes, causing pain, bleeding, or discomfort during sexual intercourse. Using a lubricant can help relieve these symptoms. Radiotherapy can also cause scarring and narrowing of the vaginal opening, which may make gynecological exams or sexual activity difficult. Dilators—usually provided by your local clinic—can help prevent narrowing. You may need to adjust the size over time.

Lymphoedema
Radiotherapy can sometimes cause lymphoedema—swelling due to accumulation of lymphatic fluid in the legs or other body areas. Affected parts may feel swollen, numb, or heavy. Early recognition is important so that treatment—such as physiotherapy, compression, or other supportive measures—can be started promptly.

Radiotherapy to the Mouth and Throat

Radiation to the throat can affect the taste buds, resulting in changes or loss of taste. This can make eating difficult or unpleasant. Taste often begins to recover a few weeks to several months after treatment, but in some cases, recovery may take up to a year or longer—and sometimes taste changes can be permanent. A dietician can advise you on how to adapt your diet so you can eat as well and as varied as possible during and after treatment.

The lining of the throat may react to radiation, with the first sign often being a sensation of a lump in your throat. This can progress to pain and swallowing difficulties. Medications are available to relieve the pain and help with swallowing and oral hygiene.

Difficulties in the throat and mouth can make eating hard, leading to weight loss. It’s important to try to maintain your weight during radiotherapy—talk to your doctor if you notice weight loss.

Oral mucosa irritation also makes the mouth more prone to fungal infections, so good oral hygiene is especially important. Radiation can reduce saliva production, lowering your mouth’s natural defenses and causing dry mouth. Saliva replacement sprays and lozenges may help; these products should be used even after treatment since dry mouth can sometimes become permanent. Regular brushing, careful cleaning of teeth, and the help of a dental hygienist can also reduce discomfort—ask your doctor about this support.

Good oral hygiene and advice from dental or nutrition specialists can make a big difference during and after radiotherapy for the mouth and throat region.