Radioactive seed implants, a form of internal radiation therapy known as brachytherapy, are a highly precise method for treating localized cancers, most commonly prostate cancer. These implants are small, pellet-like sources of radiation, roughly the size of a grain of rice, placed directly into the tumor site. The treatment is designed to deliver a high dose of radiation directly to the cancerous tissue while minimizing exposure to the rest of the body. The overall risk profile is manageable due to the careful management and containment of the radiation.
How Radioactive Seeds Work to Minimize Systemic Risk
This technique, often called low-dose-rate (LDR) brachytherapy, uses isotopes like Iodine-125 or Palladium-103, which emit low-energy radiation. This low energy means the radiation particles have an extremely short range, traveling only a few millimeters from the seed itself. The primary benefit of this short range is the rapid drop-off in radiation dose outside the immediate target zone. The tumor receives a high dose necessary to destroy cancer cells, but the radiation level quickly becomes negligible in surrounding healthy tissues. This localized delivery reduces the risk of long-term systemic side effects and collateral damage to organs far from the implant site.
Immediate Risks and Internal Side Effects for the Patient
While the radiation is localized, it causes direct damage to the tissue immediately surrounding the seeds, resulting in expected internal side effects. In the case of prostate brachytherapy, the most frequent side effects involve the urinary and bowel systems due to their proximity to the prostate gland.
Patients commonly report an urgent and frequent need to urinate, sometimes with a burning sensation, as the urethra becomes irritated by the radiation. These urinary symptoms can be noticeable in the weeks following the procedure and may last for several months as the tissue heals. Temporary changes in bowel function, such as increased frequency, urgency, or minor rectal bleeding, can also occur due to irritation of the rectal wall.
Localized swelling and discomfort in the area of implantation, along with mild fatigue, are common experiences immediately after the procedure. Though rare, a small percentage of patients may experience temporary urinary retention, requiring temporary catheterization. These internal reactions are generally manageable and gradually lessen as the radiation source loses its potency over time.
Safety Protocols for Protecting Loved Ones
Although the radiation is low-energy and short-range, temporary precautions are necessary to protect external contacts, especially those sensitive to radiation exposure. The primary concern is for pregnant individuals and small children, as their developing cells are more susceptible to radiation effects.
For a period, typically one to two months after implantation, patients are advised to limit prolonged, close contact with these groups. This includes avoiding holding small children on the lap for extended periods or sleeping in the same bed with a pregnant partner. Simple, brief contact, such as a quick hug or handshake, is permissible.
Patients are also instructed to use a condom during sexual intercourse for the first few weeks to two months, as there is a rare possibility of a seed being passed in the semen. Patients should be aware that an implanted seed could, rarely, be passed out of the body through urination, usually within the first week.
If this occurs, patients must retrieve the seed using tweezers or tongs and contact their care team for proper disposal. Patients are also provided with a medical card detailing their implant, which is helpful to present to airport security, as the seeds can trigger sensitive radiation detectors during travel.
Long-Term Fate of the Seeds
The long-term safety of the seeds is determined by the natural process of radioactive decay, which eliminates any lasting radiation danger. The radioactive isotopes used diminish their radiation output over a period of weeks or months. For instance, Iodine-125 loses half its radioactivity approximately every 60 days, while Palladium-103 decays faster, losing half its energy about every 17 days.
As the radiation dissipates, the seeds become biologically inert, meaning they no longer emit therapeutic radiation. Within 6 to 12 months, depending on the isotope used, the seeds are effectively non-radioactive. These tiny metal capsules remain permanently in the body as inert markers, posing no future radiation risk to the patient or anyone else.