If you or someone you love has cancer, chances are at some point radiation therapy will become part of the treatment regimen since 2/3 of all cancer patients will receive radiation at some point during their care. However, most patients are not very familiar with radiation therapy leading to anxiety and confusion. This article was written to try to alleviate fear and clear up some of the common misconceptions surrounding radiation treatment.
What is radiation therapy and how does it work?
Radiation therapy (radiotherapy or radiation treatment) is the use of radiation to treat various types of abnormal growth in the body. Most of the abnormal growth we treat is in the form of a cancer, but we also treat benign growths such as meningiomas, keloids and desmoid tumors that are local growth processes that do not spread throughout the body like a cancer does. Radiation is most commonly given in the form of x-rays, which are invisible light particles that can pass through the body and treat tumor cells. Radiation works to control tumors by several different ways, but the most prominent is its ability to damage DNA, the genetic material that the tumor uses to grow and multiply. When a tumor cell sustains sufficient DNA damage, it can no longer reproduce and will die. One analogy is that tumors are like “cassette tapes trying to make copies of themselves.” Radiation effectively “cuts that cassette tape” leaving it “broken” and unusable. Conceivably, the more radiation that is given to a tumor, the more likely that tumor will be destroyed. However, normal cells of the body can also be damaged by radiation that necessitates limitations on how much radiation is given and how it is delivered. Fortunately, normal cells of the body have ways of repairing radiation injury that cancer cells typically do not use. Therefore, there are two main approaches in modern radiation therapy that allow us to maximize tumor control and minimize normal tissue injury: 1) Break up treatments into smaller pieces, or fractions, that give the normal tissue an opportunity to repair the damage; and 2) Deliver the radiation better by giving more dose to tumor and less dose to normal tissue. These principles are applied to every patient we treat.
What are the different types of radiation?
As mentioned above, most radiation is in the form of x-rays (or photons) that are invisible light particles generated by machines called linear accelerators. X-rays and other commonly used forms of radiation such as electrons and gamma-rays are aimed at the patient’s tumor from outside the body because they have penetrating power. This external beam radiation therapy (EBRT) can be thought of like a “flashlight” in that we “shine” it on particular regions of the body. As the “light” passes through the body, a portion of the beam’s energy will be delivered to that tissue. We have very sophisticated ways of shining the radiation light that allows us to spare normal tissue while maximally treating the tumor. In most cases, the radiation is given from multiple angles (or fields) and can be shaped by a computer-controlled mechanism that can help shield critical organs that are in the path of radiation. Intensity modulated radiation therapy (IMRT), stereotactic radiosurgery (SRS) and body radiation therapy (SBRT) are radiation delivery techniques that maximize the principle of radiation dose shaping.
Another form of radiation is internal radiation therapy that can be given as “liquid” radiation medicine, commonly used in thyroid cancers, or in the form of brachytherapy, which literally means “short” therapy, involving tiny radioactive sources being implanted inside the body. The radiation used in internal radiation therapy does not penetrate very far and so the radioactive sources must be in close proximity to the tumor cells.
What can I expect?
Most patients are introduced to radiation oncologists during a consultation that may take place in a clinic or a hospital setting. Radiation oncologists will work with primary care physicians and other cancer specialists such as surgeons and medical oncologists to decide if radiation therapy is indicated. If radiation therapy is indicated, then the patient will be set up for a radiation simulation, or “planning session” that typically involves a specialized CT simulation scan that allows us to generate a 3D model of the patient’s anatomy for planning purposes. Depending on how sophisticated the plan needs to be to achieve the treatment objectives, it may take several days to design and quality check a treatment plan. Since most patients will receive anywhere from 10 to 35 radiation treatments given on a daily basis (Monday through Friday), we need to be sure that the patient is setup and treated the same way each time. To do this, we use both immobilization (designed at time of CT simulation) and imaging techniques to provide assurance of accurate and reproducible therapy. Most daily treatments take only a few minutes and you cannot really “feel” radiation treatments. However, because side effects can occur during the course of radiation, patients are evaluated by the nurse and radiation oncologist at least once a week.
What are the side effects?
Radiation, much like surgery, is a local and regional therapy, that is, radiation is usually aimed at only a portion of the body. As such, all of the “good parts” and “bad parts” of radiation are where we shine the beam. Because we can generate detailed radiation dose “maps” (radiation dosimetry) for each patient’s anatomy, we have some idea about the possible risks of toxicity for any given treatment plan. In general, we talk about acute (early) and late side effects of therapy. Acute effects are usually temporary and occur in normal tissues that are most rapidly dividing (since they are actively using their DNA, much like the tumor cells). For example, breast cancer treatments may cause a skin reaction much like a sunburn, while radiation treatment to the belly can cause nausea and diarrhea due to injury to the digestive system cells. These symptoms do not usually occur right away. As such, the first third of a treatment course is considered the “honeymoon period” in which little to no toxicity occurs. After that, side effects usually appear gradually and will be managed by your doctor – so be sure to tell your nurse and doctor about any symptoms you may be experiencing. The most common side effect for all therapy is a mild tiredness that feels similar to the fatigue caused by a common cold. In fact, many patients can continue to maintain their normal daily activities, including work, while receiving radiation. Late effects of radiation develop after the radiation treatment is finished, and are much less common. Patients will follow-up with their radiation oncologists and will be monitored for these late effects.
Is radiation therapy safe?
Some patients are nervous about the safety of radiation therapy. Fortunately, radiation therapy has been used for over a century and during that time we have learned a lot about how best to deliver the therapy. As described above, radiation treatments are customized and carefully planned to avoid treating healthy organs in the target region. Indeed, the extent of quality control for radiation therapy surpasses many fields of medicine. The radiation oncology team includes medical physicists who work closely with radiation oncologists to maintain the highest level of safety and quality control. The vast majority of the work that goes into radiation treatment occurs before the very first treatment is given. Treatment plans are evaluated using our specialized treatment planning software, and verification measurements and calculations are performed prior to therapy. In addition, each patient’s plan is reviewed by several radiation oncologists on faculty to ensure that the treatment plan is safe. Furthermore, our radiation treatment machines have multiple fail-safe measures built in to further protect the safety of our patients. During a treatment course, members of the radiation oncology team will recheck your treatment plan as well.
If you receive external beam radiation therapy (EBRT), you pose no risk to others as you will not be radioactive following radiation treatment. You can think of EBRT as light switch – when it is on, the radiation photons are present but when it is off, there are no photons. Brachytherapy, however, does involve the implantation of very small radioactive seeds that may be present permanently or temporarily. Similarly, “liquid radiation” in the form of radioactive medicine will require special precautions for a short period of time that will be explained to you by your radiation oncologist.
All in all, your safety is our utmost concern, which is why we have such a rigorous quality assurance program in the Radiation Oncology Department at UAB!