Radiation therapy may be lifesaving, but it can also cause short-term and long-term side effects.

Radiation therapy is one of the most common treatments for prostate cancer. It’s commonly used to treat prostate cancer in earlier stages but has been used in later stages as well.

Three types of radiation therapy are used to treat prostate cancer:

  • External beam therapy: External beam radiation therapy involves aiming beams of radiation from a machine outside of your body.
  • Brachytherapy: Brachytherapy involves implanting radioactive pellets, or “seeds,” about the size of grains of rice into your prostate. A high dose may be implanted for several minutes, or a lower dose may be administered for weeks to months.
  • Radiopharmaceuticals: Radiopharmaceuticals are radioactive drugs that are injected into a vein. The drugs travel through your bloodstream and give off radiation that kills cancer cells.

Radiation therapy can be potentially lifesaving, but it can also cause short-term or long-term side effects. Here’s a look at some of the potential side effects and how long you can expect them to last.

Radiation therapy side effects often start in the second or third week of your treatment. Some side effects can occur immediately after or days after radiation.

External beam radiation therapy side effects

External beam radiation therapy can lead to:

Brachytherapy side effects

Potential side effects of brachytherapy include:

  • bowel problems
  • urinary problems
  • erectile dysfunction

If you receive high-dose brachytherapy, you may have pain or swelling between your scrotum and rectum. Your urine may also turn reddish-brown.

If you have low-dose brachytherapy, there’s a risk of:

  • setting off airport detection systems
  • seeds passing out of your body through your urine
  • seeds moving through your bloodstream to other areas

Your doctor may advise avoiding contact with pregnant people or small children while you have seeds implanted, since you may give off a small amount of radiation.

Radiopharmaceutical side effects

Potential side effects of radiopharmaceuticals include weight loss and weakness as a result of radiation exposure, as well as:

Most radiation therapy side effects go away after weeks to months, but some can last longer. Some may not develop until months or even years after your treatment.

According to the Prostate Cancer Foundation, less than 5% of men have long-term complications of prostate cancer.

Long-term side effects can include:

  • urinary problems
  • erectile dysfunction
  • swollen legs or scrotum
  • bowel problems
  • ulcer in your rectum
  • bone problems
  • low vitamin B12

Fatigue might linger after your therapy for weeks to months after treatment.

According to Cancer Research UK, about 50% of men who receive radiation therapy for prostate cancer experience urine leakage after 6 years.

Radiation therapy and risk of a second cancer

Radiation therapy can damage cells around the area being treated and slightly increase your risk of developing another cancer. Research suggests radiation therapy for prostate cancer increases your risk of rectal cancer or acute myeloid leukemia.

It’s thought that the risk of a second cancer becomes higher with increasing dosages of radiation.

Radiation therapy can be lifesaving for some people with prostate cancer. For people who need it, the advantages outweigh the risk of side effects.

A doctor can help you weigh the pros and cons of radiation therapy and help you decide if you may benefit more from another treatment option such as surgery or monitoring the growth of the cancer.

Learn about other treatment options for prostate cancer.

According to the American Cancer Society, you generally undergo external beam radiation therapy 5 days per week for at least several weeks. Most people go for 7 or 8 weeks.

Low-dose brachytherapy pellets may be left in your prostate for weeks to months. High-dose brachytherapy is usually administered in one to four treatments over 2 days.

Radiopharmaceuticals are typically used in prostate cancer that has spread to the bone only (metastasized) and is usually injected once every 6 weeks up to six times.

Almost anybody with prostate cancer may be a candidate for radiation therapy. It’s used to treat prostate cancer in all stages.

Radiation therapy and surgery offer similar cure rates in localized prostate cancer. Radiation therapy may be a better option for older adults or people with other health issues that prevent them from safely undergoing surgery.

The best option for you largely depends on your treatment goals and personal preference. Your healthcare team can help you weigh the pros and cons of each option. You can also call the American Cancer Society’s 24/7 helpline for help making a treatment decision.

Here are some frequently asked questions people have about radiation therapy for prostate cancer.

What are the different types of radiation treatment for prostate cancer?

Three types of radiation therapy are used to treat prostate cancer.

Brachytherapy involves inserting radioactive pellets into your prostate. External beam radiation involves aiming radiation at your prostate from an external device. Radiopharmaceuticals involve taking radioactive medication through an intravenous (IV) line that travels through your bloodstream.

What is the success rate of radiation therapy for prostate cancer?

Radiation therapy is highly effective for treating prostate cancer. In a 2017 study, researchers compared the effectiveness of brachytherapy and external beam radiation in men with high-risk prostate cancer. Five years after treatment, 89% of men given brachytherapy and 84% of men given external beam radiation had no signs of cancer.

What are the most common side effects of radiation for prostate cancer?

Some of the most common side effects of radiation therapy for prostate cancer include:

  • bowel changes such as diarrhea
  • urinary changes such as frequent urination
  • erectile dysfunction
  • fatigue

What are my treatment options if radiation therapy fails?

If radiation therapy isn’t effective, your doctor may recommend surgery or hormone blocking treatments via medications. Doctors usually don’t recommend radiation therapy again, but they may recommend brachytherapy if you received external beam radiation previously.

Radiation therapy is one of the most common treatments for prostate cancer. It can be lifesaving for people who need it but can also cause many different side effects.

Some of the most common side effects of radiation therapy for prostate cancer include erectile dysfunction, urinary problems, and bowel problems. These side effects usually pass after weeks or months but can become long-term problems for some people.