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Cancer of unknown primary

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Potential side effects of radiation therapy for cancer of unknown primary

Side effects can occur with any type of treatment for cancer of unknown primary (CUP), but not everyone has them or experiences them in the same way. 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
  • if chemotherapy is also being given
    • Chemotherapy may make some of the side effects of radiation worse.

Radiation therapy damages cancer cells, but healthy cells in the treatment area can also be damaged, even though steps are taken to protect them as much as possible. Different cells and tissues in the body tolerate radiation differently.

Side effects can happen any time during radiation therapy. Some may happen during, immediately after or a few days or weeks after radiation therapy. Most side effects go away after radiation therapy is finished. However, some side effects may last for a while because it takes time for healthy cells to recover from the effects of radiation therapy. Late side effects can occur months or years after radiation therapy. Some side effects may last a long time or be permanent.

If the person with cancer of unknown primary (CUP) only receives a few radiation therapy treatments, they generally have very few side effects.

It is important to report side effects to the healthcare team. Many side effects can be relieved by medications, a change in diet or by other measures. Doctors may also grade (measure) how severe certain side effects are. Sometimes radiation therapy treatments need to be adjusted if side effects are severe.

Skin reactions

Skin reactions occur because external beam radiation travels through the skin to reach the area being targeted for treatment. The skin in the radiated area may become red, dry, 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 persist. Some people do not experience any skin reactions with radiation therapy.

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Fatigue is one of the most common side effects of radiation therapy. Fatigue can occur for a variety of reasons. During radiation therapy, the body uses more energy to heal itself, so fatigue will not always be relieved by rest. Making frequent, daily trips for radiation treatments can also be tiring. Radiation therapy to any area of the body can make a person feel more tired than usual, but is more common when larger areas of the body are treated.

Fatigue usually occurs during the second week of radiation treatment or later. 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.

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Side effects by treatment area

Other side effects depend on how much radiation therapy is given and the area of the body treated.

Radiation therapy to the head and neck

Radiation therapy to the head and neck can cause a sore throat, dry mouth and difficult or painful swallowing. Other side effects can also occur, including loss of appetite, taste changes and jaw problems. Most side effects usually begin 2–3 weeks after starting treatment. Most side effects go away once treatment is over, but a few may persist or occur after radiation treatment.

Radiation therapy to lymph nodes

Radiation therapy to lymph nodes under the arm or to the breast can cause changes in skin texture and sensation in the treated area. It may also cause shoulder stiffness. Changes to the breast usually continue for a few months after radiation therapy is finished, but can last longer.

Radiation therapy to lymph nodes in the groin can cause swelling of the legs (lymphedema). This can occur if radiation therapy to lymph node areas causes scarring, blockage or slowing of the lymph flow. Lymphedema may develop during a course of radiation therapy or several weeks after radiation therapy is finished. This is often a long-term side effect.

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