Brachytherapy can cause both short-term and long-term side effects that affect your bowel, urinary tract, and sexual health.

Brachytherapy, also called seed implants, is a type of radiation therapy used to treat prostate cancer. It involves implanting tiny radioactive pellets into your prostate gland that emit energy and destroy cancer cells.

Doctors sometimes recommend brachytherapy by itself for people with low-risk and early stage prostate cancer. It’s sometimes used in combination with external beam radiation therapy for cancer at risk of growing beyond the prostate.

Brachytherapy may control low- to intermediate-risk prostate cancer — studies show that 85%–97% of individuals receiving brachytherapy are cancer free 5 years after treatment.

This article specifically looks at the long-term side effects of this treatment for prostate cancer.

Doctors use two types of brachytherapy for treating prostate cancer:

  • Permanent brachytherapy: About 100 radioactive pellets are inserted into your prostate that release a lower dose of radiation than temporary brachytherapy for weeks to months.
  • Temporary brachytherapy: Radioactive pellets are placed inside your prostate for 5–15 minutes at a higher dose than permanent brachytherapy. Usually, you receive 1–4 treatments over 2 days.

There currently isn’t direct evidence that either of these two treatments is better than the other in terms of side effects and tumor control rates. Potential long-term side effects include the following.

Bowel changes

Serious long-term bowel problems are uncommon among people who receive brachytherapy. But, potential side effects include:

In a 2019 study, researchers examined late bowel side effects in 620 people who received brachytherapy for prostate cancer. Of these people, almost two-thirds received brachytherapy alone, and 12.4% had significant rectal bleeding at a median follow-up of 4 years.

In a 2020 study, researchers reported a 1.9% rate of moderate to severe rectal side effects after 2 years among people treated with permanent brachytherapy.

Urinary tract changes

Some people have long-term urinary complications, such as:

A small percentage of people develop bladder cancer after receiving brachytherapy. When this happens, it’s usually in the first 10 years. In a 2022 study, 1.5% of 969 people treated with brachytherapy at one hospital in Japan developed bladder cancer.

Erectile changes

Radiation can damage the nerves in your penis and impair your ability to get or maintain an erection. Among people who receive temporary brachytherapy, long-term side effects affecting the urinary tract or penis have been reported in 0.2%–14% of people.

In a 2019 study, researchers found that more than half of men receiving permanent brachytherapy maintained a score over 16 on the IIEF-5; a five-question survey measuring erectile function. A score of 16 correlates with a “high” level of satisfaction. Severe erectile dysfunction was very rare.

Most side effects of brachytherapy only last days to weeks. It’s important to speak with a doctor if you have side effects that last beyond this period or that you find concerning.

Some symptoms require immediate medical attention. It’s important to get immediate medical attention if you develop:

Short-term side effects of brachytherapy are similar to long-term side effects. They include:

Your doctor may advise you to stay away from young children and pregnant women for the first few months after you receive permanent brachytherapy.

Side effects usually start to get better within weeks. Although it’s not common, some people may have side effects for years or the rest of their lives.

In a 2020 study, researchers found that people reported the maximum number of urinary and sexual symptoms at a 6-week follow-up and mild impairment at 10 years. Those were the two ends of follow-up appointments.

Brachytherapy is an important part of cancer treatment for some people. It can potentially cure your cancer and remove the need for surgery. Surgery has been associated with higher rates of long-term side effects in some studies.

Brachytherapy is a treatment option by itself for people with low- to intermediate-risk prostate cancer. It may be combined with external beam radiation therapy for men with high-risk disease.

Who should avoid this treatment?

Brachytherapy may not be a treatment option if you have:

  • cancer spread to distant body parts
  • large prostate and urethral defects
  • ataxia telangiectasia, a neurodegenerative condition
  • limited life expectancy

Here are some frequently asked questions people have about seed implants for prostate cancer.

How long do prostate seed implants last?

Permanent brachytherapy seeds release their radiation over weeks to months. In the first months after your treatment, the radiation may be detected by border crossing officials (for those considering travel).

How successful is brachytherapy for prostate cancer?

Brachytherapy has high success rates for people who are candidates. In a 2023 study, researchers reported a 98% biochemical control rate after 7 years among 149 people treated at one institution from 2006 to 2021.

Brachytherapy can cause long-term side effects that affect your urinary, sexual, or bowel health. Rates of long-term side effects are relatively low.

Although it’s rare, some people may develop serious side effects such as a complete inability to pass urine or stool. It’s important to report any concerning symptoms to a healthcare professional.