Radiation therapy is used to locally treat cancer using high energy rays. Radiation therapy is typically done after surgery to remove the tumor. The surgery site should be healed before starting radiation, which can take about a month. For those receiving chemotherapy as well, radiation is generally done afterwards.1

The main types of radiation therapy are external beam radiation therapy (EBRT) and brachytherapy. EBRT is the most common type of radiation therapy and involves a machine outside of the body that directs the radiation beams to the desired area. If cancer was found in the lymph nodes this area will also be given radiation.1 EBRT is similar to an x-ray, but with stronger radiation. Ink marks or tattoos will be used to mark the area of the body receiving radiation, and the radiation team will maneuver the machine to find the correct angles.1

The typical radiation therapy schedule for radiation is 5 days a week for 6-7 weeks. However, there are options that use higher doses of radiation for shorter durations such as hypofractionated radiation therapy. For this method, radiation is usually given 5 days a week for about 3-4 weeks due to the larger daily doses. Studies have shown that hypofractionated radiation therapy results in equivalent recurrence rates as the standard radiation schedule. This method may also help minimize short-term side effects.1

Brachytherapy, also known as internal radiation, involves placing radioactive seeds or pellets inside the body. The main types of brachytherapy are intracavitary brachytherapy and interstitial brachytherapy. In this method, a device is inserted into the tumor bed using a catheter. The end of the device is then expanded like a balloon to keep it in place. The other end of the catheter sticks out of the breast where the radioactive material can be added. The radioactive material is removed from the device between treatments. Intracavitary brachytherapy treatments are generally given two times a day for 5 days. After the final treatment, the device can be deflated and removed. Interstitial brachytherapy involves inserting several catheters around tumor area. In this method, the radioactive material is inserted into the catheters for short durations each day and then removed. Interstitial brachytherapy was the original method of brachytherapy, but it is used less frequently today than intracavitary brachytherapy.1

Accelerated partial breast irradiation (APBI) is another method of radiation therapy that gives larger doses over a shorter period of time. APBI focuses the radiation on a portion of the breast rather than the whole breast.1 Proton beam therapy is a type of APBI. The use of protons allows for increased precision because they are easier to control and do not travel beyond the tumor.3

Brachytherapy falls under the category of APBI, but there are additional types of external APBI methods as well. Intraoperative radiation therapy (IORT) uses special equipment to deliver a single large dose of radiation to the tumor bed right after a lumpectomy, before the incision is closed. 3D-conformal radiotherapy (3D-CRT) uses special machines with better aim to deliver the radiation more directly. For 3D-CRT, treatments are typically given two times a day for 5 days. Intensity-modulated radiotherapy (IMRT) is a modified form of 3D-CRT that also alters the intensity of the radiation beams in certain areas, allowing the tumor bed to receive high doses and the surrounding normal tissues to be less affected.1

 References

1.     Radiation for Breast Cancer https://www.cancer.org/cancer/breast-cancer/treatment/radiation-for-breast-cancer.html (accessed May 24, 2021).

2.     Breast Cancer Surgery https://www.cancer.org/cancer/breast-cancer/treatment/surgery-for-breast-cancer.html (accessed May 21, 2021).

3.     Proton Beam Therapy Program https://www.mayoclinic.org/departments-centers/proton-beam-therapy-program/sections/overview/ovc-20185491 (accessed May 26, 2021).