Brachytherapy
Brachytherapy, or internal radiation therapy, is an important modality of treatment for cancers. It can be used alone or with external beam radiation therapy (done on linear accelerators). Brachy in Greek means short or near, which means the radiation source is kept in contact with the patient’s body. In this procedure, we place sealed radioactive sources close to the target. The absorbed dose falls off rapidly with increasing distance from the source; high doses may be delivered safely to a localised target region over a short period of time.
IMPLANTATION TECHNIQUES - Depends on the approach to the target, it consists of:
Intracavitary brachytherapy:
It consists of positioning applicators into a body cavity, commonly used for gynecologic malignancies and post-operative breast cancers. These are temporary implants left in the patient's body for a specified time to deliver a prescribed dose.
Interstitial brachytherapy:
It involves surgically implanting small radioactive sources directly into the target tissue. Permanent implants are kept in low-risk Prostate cancers where iodine pellets are implanted into the prostate, and they keep decaying over a period of time after delivering an initial prescribed dose. Temporary implants are surgically placed in the tumour bed during surgery (Ca Breast, Soft tissue Sarcoma) or in case of recurrent tumours of the tongue.
Transluminal brachytherapy :
This consists of inserting a single line source into a body lumen like the esophagus or bronchus for their respective cancers as a boost or palliation.
Surface dose applicators:
It is designed in a way to deliver uniform doses to the skin or a mucosal surface (skin cancers, penile cancers).
ADVANTAGES OF BRACHYTHERAPY:
- 1. High localised radiation dose i.e., high local control.
- 2. Avoids surrounding healthy organs, thus fewer side effects.
- 3. Ultimate form of conformal radiotherapy.
- 4. Homogenous dose distribution to tumour targeting the hypoxic central core.
Radionuclides in use -
- 1. IRIDIUM-192
- 2. IODINE-125
- 3. COBALT-60
- 4. PALLADIUM-103
PROCEDURE
The most commonly used radionuclide for high-dose-rate brachytherapy is Iridium-192. It is a gamma ray emitter and has a half-life of 74 days.
At Omega Hospitals, Hyderabad, we have a micro selectron Brachytherapy After loading Platform, which uses Iridium192.
Procedures are usually done outpatient, commonly in Ca Cervix and Ca Endometrium cases; 3 to 5 (15Gy-25Gy) sittings of Internal radiation therapy are usually performed on patients after external beam radiotherapy.
After checking the vitals and examination of the patient, they are taken to the brachytherapy unit and asked to lie down on the couch in a lithotomy position. In case the patient experiences pain during the procedure, a painkiller injection is given. For an unoperated case, Ca Cervix Tandem and Ovoid set are used. In post-op cases of gynaecological cancers, ovoids or cylinder applicators are used.
As these applicators are placed in natural body cavities, these procedures are not really uncomfortable or painful, and patients are well managed on an outpatient basis.
CYLINDER
After placing the applicator, a CT SCAN of the patient is taken with the applicator in situ, and then the planning of dose delivery is done on the same images on Oncentra TPS. The dose is delivered over 15-30 mins, and then all the applicators are removed slowly and parts cleaned. The patient will be called again after 1 week with blood tests for the same procedure.
CONCLUSION
To conclude, brachytherapy is an important adjuvant treatment modality in gynaecological cancers. This is a tried and tested golden method for conformal cancer treatment with fewer early and late complications of treatment.
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