Radioactive seed implants are a method of internal radiation therapy, known as brachytherapy, tailored for certain patients with early-stage breast cancer. This localized approach is most often employed following a lumpectomy, which is a breast-conserving surgery. The technique falls under Accelerated Partial Breast Irradiation (APBI) because it focuses the radiation dose only on the tissue immediately surrounding the original tumor bed, rather than treating the entire breast. This concentrated delivery reduces overall treatment time and minimizes radiation exposure to nearby healthy organs.
The Mechanism of Seed Implants
These implants consist of tiny, rice-sized capsules permanently placed into the breast tissue. Each seed contains a low-dose radioactive isotope, such as Palladium-103 or Iodine-125. The choice of isotope is often determined by safety considerations. Once positioned, the seeds deliver radiation continuously and slowly over weeks or months until the material naturally decays. This process administers a high, concentrated dose directly to the surgical cavity, where residual cancer cells are most likely to exist. The highly localized nature of this radiation minimizes the dose received by surrounding structures like the heart, lungs, and skin.
Patient Eligibility and Selection
Candidates for this localized radiation treatment must meet specific clinical criteria, indicating a low risk for recurrence outside the immediate tumor area. This treatment is generally reserved for women diagnosed with early-stage breast cancer, including invasive carcinoma or ductal carcinoma in situ (DCIS). Key requirements include having clear surgical margins following the lumpectomy. Patients are typically 50 years of age or older, and the original tumor size is usually limited to a maximum of 3 centimeters. Furthermore, the cancer should not have spread to the lymph nodes, meaning the sentinel lymph node biopsy must be negative. This selective approach, known as partial breast irradiation, contrasts with Whole Breast Radiation Therapy (WBRT), which treats the entire breast.
The Procedure: Placement and Delivery
The implantation of permanent radioactive seeds is usually a single procedure performed after the breast-conserving surgery has healed. The patient may receive local anesthesia, light sedation, or general anesthesia. Before the procedure, a computed tomography (CT) scan is used to precisely map the tumor bed and plan the exact placement of the seeds.
During the procedure, a specialized brachytherapy template guides hollow needles into the breast tissue surrounding the lumpectomy cavity. The radioactive seeds, often pre-stranded together, are then inserted through these needles into the planned locations. Imaging guidance, such as ultrasound or fluoroscopy, ensures the seeds are accurately deposited around the surgical site. Once the needles are withdrawn, the seeds remain permanently within the breast tissue.
Post-Treatment Care and Safety
Immediate post-treatment care involves managing minor side effects at the implant site, such as soreness, bruising, or swelling. Patients can usually resume most normal daily activities shortly after the procedure. Because the radiation is permanently sealed within the metal seeds, the risk of external exposure is extremely low.
Despite the low-energy nature of the radiation, patients are advised to take temporary precautions when the seeds are most active. This guidance often includes limiting prolonged, close contact with pregnant women and young children. The highly localized radiation is shielded by the surrounding breast tissue, and the seeds become biologically inert over time as the radioactive material decays. Routine follow-up care is then scheduled to monitor the treatment area.