Types of Radiation

There are three main types of radiation, External, Internal and Intra-operative

External Radiation: It is the most commonest radiation to be given, it is given through a large machine called a linear accelerator. This machine aims a beam of high-energy radiation at the area affected by the cancer. It is also referred to as external beam radiation. Subject to the requirement it is given in the OPD and no admission is required. It may be given for upto 5 days in a week for duration of nearly 5 -7 weeks. If the radiation is being given to the breast it is directed from 2 separate treatment fields, which come from against each other i.e. opposite direction and face each other. One initiates from the middle of the chest and faces the side and the other vice versa. In case lymph nodes also need to be exposed to radiation, additional radiation treatment fields are added.

Once the tenure of the radiation is coming to an end post 5 – 7 weeks) towards the completion of the procedure, an external radiation boost is also given. It is essentially a supplemental dose of radiation rays which are again targeted and aimed t the original site of cancer where it was and operated. The method of administration of the booster dose is same as regular radiation.

Internal Radiation: This is a lesser applied form of radiation. It is still under study for patients post lumpectomy. It is also referred to as partial breast radiation and brachytherapy. In this procedure usually, seeds (which are small tiny pieces of radioactive content) are placed at the site of cancer where it was before being operated upon. As it is placed at the original site it is surrounded by the tissue closest to the cancer cells and highest recurrence risk, these seeds project radiation rays and destroy cancer cells from inside.

The deliver these seeds in the tissue at the cancer site, two methods are used. It may be done by many small catheters which are tubes like structure. Or a device called MammoSite may be used to put these seeds in at the cancer site. MammoSite is a balloon catheter.

When multi-catheter is used in internal radiation, it is done by sewing tiny tubes (catheters) under the skin in the area at the site of the cancer. There are little holes in the skin through which the ends of the tubes stick out. These tubes are held in plce with tiny stitches. Radioactive material seeds are placed in the catheters by the doctor or a machine for duration sufficient for delivery of the prescribed dose. The treatment may last longer and take a few days, in case low-dose radiation seeds are being used. As the patient has radioactivity inside the body during the course of treatment, she has to stay in the hospital premises and as such admission is required for this procedure. On completion of the radiation treatment, doctor removes the radioactive seeds, stitches, and tubes, discharging the patient. In case of high-dose radioactive seeds, the seeds remain in the tissue at the site for up to 10 minutes, then removed and patient sent home. The seeds are then removed and you are free to leave the treatment center. The tubes may remain in place till the course of the treatment is completed, it may last 1 week (5 days), with 2 treatments each day.

In a balloon-catheter system also for internal radiation the balloon is placed at the site of cancer. This is done very carefully and the tube exits though a small opening in the skin. This mammoSite system balloon is filled with fluid, which keeps the balloon and the tube stationed at the site. This tube stays like this for a week and it can be inserted in the doctors clinic or in an operating room. The treatment course ranges upto 5 days with 10 treatment lots of 5 – 10 minutes each. Thus coming to 2 treatments per day. Once the course is complete, the balloon is removed through the small hole in the skin.

Similar to external radiation boost, Internal radiation boost also exists. Though it is given at the completion of external radiation treatment.

Intraoperative Radiation: This is also a recent advancement in radiation therapy and is administered during the lumpectomy surgery to the patient after the cancer cells have been removed from the site. It is abbreviated as IORT. In it a very high dose of radiation is aimed or targeted directly at the site of the cancer while the underlying breast tissue is still exposed.

There are two techniques to deliver intraoperative radiation. In one linear accelerator is used which same as used in external radiation. The electron beam is targeted at the risk area for about 2 minutes and the surgery then proceeded in usual manner. With extra special technique the underlying healthy tissue is protected from the radiation exposure.

In the other technique, a small tube is used to target and deliver a high dose of radiation. This tube is placed at the site of cancer growth and takes a time period of 5 – 10 minutes. It is referred to as high-dose-rate remote afterloading intraoperative radiation.

There are conflicting opinions of the medical fraternity on benefits of intraoperative radiation therapy to whole-breast radiation after lumpectomy, which is the standard of care.

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