Adverse Effects of Radiation Therapy

Excerpt

Overall, cancer rates are projected to increase from approximately 9 million in 2017 to approximately 26 million new cancer cases by 2030. About 30% to 50% of all cancer patients receive irradiation either alone or with chemotherapy and surgery. Therefore, around 7 million patients receive radiotherapy worldwide every year. Improved cure rates of all malignancies have resulted in more providers being confronted with a large number of patients with a wide range of chronic morbidities in long-term survivors. Hence all providers must be aware of the common adverse effects of radiation therapy.

There are different types of radiation therapy. Two major types are external-beam radiation therapy and internal radiation therapy. External-beam radiation therapy is the most common type and delivers radiation from a machine outside the body. The types of external-beam radiation therapy are:

Three-Dimensional Conformal Radiation Therapy (3D-CRT) - Three-dimensional pictures of the cancer are created, from CT or MRI scans. This allows aiming the radiation therapy more precisely. It means that higher doses of radiation therapy can be used while reducing damage to healthy tissue. This lowers the risk of side effects.

Intensity Modulated Radiation Therapy (IMRT) - This is a more complex form of radiation. With IMRT, the intensity of the radiation is varied within each field unlike conventional 3D-CRT, which uses the same intensity throughout each beam. IMRT targets the tumor and avoids healthy tissue better than conventional 3D-CRT.

Proton Beam Therapy - This treatment uses protons rather than x-rays. At high energy, protons can destroy cancer cells. The protons deposit the specific dose of radiation therapy to the targeted tissue. There is very little radiation dose beyond the tumor as compared to x-rays. This limits damage to nearby healthy tissue.

Image-Guided Radiation Therapy (IGRT) - Daily images of each treatment field to confirm patient positioning are taken to make sure the target is in the field. This allows better targeting of the tumor and helps reduce damage to healthy tissue.

Stereotactic Radiation Therapy (SRT) - This treatment delivers a large, precise radiation therapy dose to a small tumor area. SRT is often given as a single treatment or in lesser than 10 treatments.

Internal radiation therapy is also called brachytherapy. In this type of radiation therapy, radioactive material is placed into cancer or surrounding tissue.

Types of internal radiation therapy include:

Permanent Implants - These are tiny steel seeds about the size of a grain of rice that contains radioactive material. They deliver most of the radiation therapy around the implant area. Some radiation may exit the patient’s body and thus requires safety measures to protect others from radiation exposure.

Temporary Internal Radiation Therapy - Radiation therapy is given via needles, catheters, and special applicators. The radiation stays in the body from a few minutes to a few days. Most people receive radiation therapy for just a few minutes, some may receive for more time.

Side effects of radiotherapy are classified as acute (early), consequential, or late effects on normal tissues over time. Acute radiation toxicity is seen within a few weeks after treatment and usually involves intermitotic cells (skin and mucosa). Consequential effects are seen when acute complications are not treated and cause persistent damage. Late complications emerge months to years after exposure and usually involve postmitotic cells (liver, kidney, heart, muscle, and bone). This chapter briefly outlines a review of common complications of radiotherapy.