Exploration of External Beam Radiation Therapy Treatment for Breast Cancer Patients
In 1896, Wilhem Conrad Roentgen (a German physics professor) presented a lecture introducing the x-ray. There was immediate worldwide excitement and systems were quickly developed to utilize this new technology and within three years x-rays were being used to treat cancer. The American Cancer Society (2014) describes that it was common for early radiologists use themselves to test the strength of the radiation coming from machines. They would use the skin on their arms to find a dosage that would produce a sunburn like reaction. This was called the “erythema dose” and was used as an estimate of the daily fraction to treat patients. This testing led to the discovery that radiation could cause cancer as many of these radiologists developed leukemia from the regular radiation exposure. Thankfully, methods and machines for delivering radiation therapy have continued to improve. Today there are many different techniques to delivery radiation therapy including external beam radiation, brachytherapy (internal radiation), and intraoperative radiation. The goal of radiation therapy is to treat the cancerous area while protecting healthy tissues and organs. This paper will explore the use of external beam radiation therapy for patients with breast cancer. In 2018 there will be an estimated 268,670 new cases of breast cancer – 266,120 for women and 2,550 for men (Siegel, Miller, & Jemal, 2018).,
Among women, this represents the largest number of new cases and the second leading cause of cancer death. According to the American Cancer Society (2017), external beam radiation is the most common type of radiation treatment for breast cancer. The American Cancer Society (2017) outlines common situations in which external beam radiation therapy is used:
- Following breast conserving surgery. Typically, the entire breast is treated (whole breast radiation) and a boost of radiation directed at the site where the cancer was removed. The boost is often given after the whole breast radiation treatment.
- Following a mastectomy with no lymph node involvement. Typically, the radiation is directed at the chest wall, mastectomy scar, and location of any drains exiting the body.
If cancer was detected in lymph nodes, radiation treatment may be directed at these areas, commonly the axillary lymph nodes, supraclavicular lymph nodes, and internal mammary lymph nodes. Traditionally radiation treatment is performed five days a week for about five to six weeks. Accelerated breast irradiation is now being performed giving patients a larger dose over a shorter time.
The American Cancer Society (2017) outlines these types:
- Hypofractionated radiation therapy – larger doses of radiation given in fewer treatments, usually for three weeks. For patients who had breast conserving surgery without cancer spread to axillary lymph nodes, results show that it is as effective in preventing cancer recurrence as treatment over five weeks and may also reduce short-term side effects.
- Intraoperative radiation therapy (IORT) – a single large dose of radiation is given in the operating room following cancer removal and prior to incision closure.
- 3D-conformal radiotherapy – computed tomography (CT) images are used to map the tumor bed and the radiation beams are directed to this area from multiple directions sparing healthy breast tissue. Treatment is given for five days, twice a day. Intensity-modulated radiation therapy (IMRT) is a newer treatment method. It is similar to conformal radiation therapy in that it uses CT images to map and direct the radiation beams from multiple directions to the treatment area. With IMRT, the strength of the radiation beams can be adjusted in each direction. Research suggests that IMRT may reduce toxicity in patients particularly in combination with partial breast irradiation in the prone position (Buwenge, et al., 2017).
Cancer of the left breast introduces the challenge of treating the area while minimizing damage to the heart from radiation exposure.Various techniques aim to do this by considering the location of the treatment area and the patient’s anatomy. IMRT can reduce the amount of radiation in the beams that pass through the heart. Prone positioning allows gravity to pull the breast away from the heart during treatment. Deep inspiration breath hold (DIBH) moves much of the heart out of the treatment field. DIBH has been shown to reduce the mean heart dose in patients while also decreasing the dose to the lungs (Bergom, Currey, Desai, Tai, & Strauss, 2018). Another modern technique is volumetric modulated arc therapy (VMAT) and is an evolution of IMRT. With IMRT, the radiation beam is directed at a fixed number of locations with each beam having its own intensity level. VMAT allows for radiation to be delivered along the entire rotation of the machine arm and for the intensity to be adjusted at each position. It seems that the research of VMAT in treating breast cancer is limited and it is unclear when this technique would result in an advantage over established methods (Cozzi, et al., 2017). Radiation therapy to treat breast cancer as well as radiation therapy in general is an ever-evolving field. Research continues to fine-tune current strategies and develop new ones.