Written by : Dr.Kishore Kumar Das, MD
Internal radiotherapy, also called Brachytherapy, is a procedure in which radioactive sources are placed inside the body very near to the tumor area. High-energy, ionizing rays from the source delivers a high dose of radiation directly to the tumor and helps spare nearby tissues.
The radiation source is usually sealed in a small holder called an implant, which may be in the form of wires, needles or a catheter. It targets the area where the cancer originally grew (called the 'tumor bed') and the tissues closest to the tumor site, killing any possible remaining cancer cells.
The implant may be placed inside the breast at the time of the surgery or soon after.
Brachytherapy may also be used to give an extra dose of radiation to the area of the excision site (called a "boost") after a lumpectomy.
The advantage of brachytherapy is that it suplies radiation very close to the site of the tumor and thus prevents or decreases radiation to the normal tissues of the chest, ribcage and lungs. The skin is also not affected unlike the traditional external radiation.
During brachytherapy, the radiation source in the body may give off radiation during the procedure, especially in high dose brachytherapy. It may be necessarry to be isolated and to avoid meeting with other people while the treatment process is on.
Types of Brachytherapy:
- Low-dose rate (LDR) Brachytherapy: In this type of brachytherapy for breast cancer, a low dose of radiation is delivered at a continuous rate over one to two days, usually over 20 to 50 hours. The delivery device remains in place throughout the treatment period. It requires an overnight stay at the hospital.
PDR or Pulsed dose-rate (PDR) treatments are a type of LDR Brachytherapy in which radiation is deliverd in periodic pulses, usually one per hour.
- High-dose rate (HDR) Brachytherapy: In this type of brachytherapy, high doses of radiation are delivered for a short time, ususally 10-20 minutes per session. Treatment may be twice a day for 2 to 5 days or once a week for 2 to 5 weeks, depending on the type of cancer. This is usually a outdoor procedure with the patient making daily trips to the hospital to have the radiation source put in place. But some patients may be admitted to the hospital for one to two days to have several HDR treatments on consecutive days using the same applicator.
During the course of treatment, the catheter or applicator may stay in place, or it may be put in place before each treatment.
Accelerated Partial Breast Irradiation (APBI)
Accelerated partial breast irradiation (APBI) is a type of HDR Brachytherapy in which the radiation is focused on just the tissues around the breast cavity left after a lumpectomy is performed.
Since the majority of recurrences in the breast occur around the site of the original lumpectomy cavity, it is rational to deliver radiation primarily to these tissues. Radiation is not delivered to the whole breast.
APBI reduces the duration of therapy to just five to seven days compared to the six to seven weeks for traditional whole-breast irradiation . It offers better cosmetic results and nearly the same efficacy as whole-breast irradiation. The criteria for receiving APBI are:
- The patient must be more than or equal to 50 years.
- It is restricted to cases of DCIS or first stage of Invasive Ductal Cancer.
- The tumor must be less than or equal to 3 cm.
- The margins of the tissues around the lumpectomy must be free of cancerous cells.
- There must be no spread to lymph nodes.
- No pre-operative chemotherapy.
Types of APBI
- SAVI Brachytherapy: SAVI Brachytherapy is usually given in women with first stage breast cancer ( ductal cancerin situ - DCIS). It utilizes a specialized implantable device that conforms to the shape of the surgical cavity left after lumpectomy and which releases radiation.
The SAVI system consists of an expandable bundle of tiny, soft and pliable catheters which can be positioned around the lumpectomy cavity and which can expand into a ball-like shape inside the lump. Radiation is delivered through these catheters. They can be inserted through a tiny incision on the breast and remains in position thorughout the course of treatment. They are removed after the treatment is over.
The SAVI device can be placed during the lumpectomy or afterwards in a separate procedure. The latter can be performed as an in-office procedure or in an outpatient clinic.
- MammoSite Brachytherapy: This device is consists of a a central strut in the center of a ballon. The strut can be loaded with the high-dose rate (HDR) source. Since the source remains in a single position in the center of the device, the dose distribution is approximately spherical. This causes equal dosing around the lumpectomy cavity. It is a single-entry device.
- Contura Brachytherapy: This is a type of balloon brachytherapy in which there are multilpe lumens inside the ballon (versus the single strut in MammoSite). Due to the additional lumens or channels, it is easier to shape or "contour" the radiation dose away from the skin or chest wall. It also employs a vacuum to help the balloon fit closely within the often irregularly shaped lumpectomy cavity, so that the targeted areas receive the prescribed therapeutic dose.
- Interstitial Brachytherapy: Also known as the Interstitial tube and button treatment technique, the implant consists of very small, hollow tubes placed under the skin. Radioactive wires are threaded through these tubes and kept in place for a few days. It requires the patient to stay in the hospital for these days. Some women treated with external radiation for breast cancer receive a 'booster dose' of radiation that may use interstitial radiation or external radiation.
This is a highly skilled procedure with multiple entry and exit points into and out of the breast.
Procedure of Brachytherapy: The type of radioactive material used (iodine, palladium, cesium or iridium) depends on the type of treatment. In all types, the radiation source is encapsulated. This means it is enclosed within a non-radioactive metallic capsule often referred to as a "seed." This helps prevent the material from moving to other parts of the patient's body.
The initial procedure of simulation is the same as in external radiation therapy . Then, under local or general anesthesia, the device is inserted into the tissues of the breast just over the site of the lumpectomy. After the device's accurate position is confirmed, the radiation wires are inserted into the tubes or a radioactive source is placed in the ballon . This is called "afterloading." The radioactive source may be placed for a few minutes every day or continuously for a few days.
Once treatment is complete, the delivery device is removed from the patient. Internal radiation typically offers fewer noticeable side effects. In nearly all cases, the appropriate method is determined by the radiation oncologist based on the location and size of the tumor.
What to Expect When the Device Is Removed
Once you finish treatment with LDR or HDR implants, the device will be removed. Here are some things to expect:
- The area where the catheter or applicator was inserted might be tender for a few weeks. Painkillers are usually prescribed for relief from the pain. The pain and tenderness usually goes away within 2 to 4 weeks of ending the treatment.
- The skin might become reddish or or darker in the treatment area. This will fade within 1-2 weeks.
- There is no radiation in the body after the catheter or applicator is removed. It is safe for people to be near the patient - even young children and pregnant women.
- There may be some amount of fatigue for a week or two and it may be necessary to limit normal activities.
Read More :
Previous: External Radiotherapy