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Understanding Radiotherapy
After being diagnosed with cancer, many people focus on how to treat it. Generally, there are three primary methods for treating cancer: surgical removal through surgery, radiation therapy, and chemotherapy. Once a patient is diagnosed with cancer, doctors will determine the appropriate treatment method based on factors such as the patient’s age, health condition, the nature of the tumor, its location, size, and the extent of its spread.
Among these, radiation therapy, commonly referred to as “radiotherapy” or “radiation” in Mainland China, works by using high-energy radiation to irradiate cancer cells within the patient’s body. This process damages the chromosomes of the cancer cells, preventing them from growing and causing them to die. Although both normal and cancer cells coexist within the patient’s body and receive the same radiation dose during treatment, normal cells are usually resting. They are less susceptible to radiation damage than cancer cells, which are in a state of division. Moreover, normal cells have a stronger ability to repair themselves. Therefore, while radiation targets and eliminates cancer cells, normal tissues may be affected but can still maintain certain functions.
Radiation therapy
Uses of Radiation Therapy
Radiation therapy serves three primary purposes:
- Cure Cancer
Also known as “curative treatment,” it can be used alone or in combination with surgery or chemotherapy before or after these treatments. This approach increases the success rate of tumor elimination and reduces the chances of cancer cell metastasis.
- Palliative Care
When tumors in the patient’s body cause various types of pain and discomfort, radiation therapy can be used to control these symptoms.
- Treatment of Benign Tumors and Diseases
It is often applied in hematology, such as for hemangiomas, keloids, or individual benign tumors.
After understanding the uses of radiation therapy, the next question is how it is carried out. Radiation therapy can be divided into external beam and internal types. Let’s start with external beam radiation therapy, which is similar to having an X-ray. The patient lies on a bed, and the doctor uses a linear accelerator to emit high-energy X-ray beams that penetrate some normal tissues within the patient’s body to reach the tumor. The process takes anywhere from a few minutes to over ten minutes. Once the beams enter the body, they gradually release energy and do not leave residual radiation within the patient’s body. Therefore, daily social interactions are not affected. External beam radiation therapy covers a larger area than internal radiation therapy, and the dose distribution within the irradiated area is relatively more uniform.
Developing an Appropriate Treatment Plan
External Beam Radiation Therapy
Treatment Plan
Before treatment begins, oncologists, radiologists, and radiation therapists work together to develop the most suitable treatment plan for the patient to achieve the best therapeutic effect while minimizing damage to normal tissues. The main factors they consider include the type, location, size of the tumor, nearby organs, and the patient’s health condition. The detailed steps for establishing the treatment plan are as follows:
1. The oncologist refers the patient’s case to the radiation therapy department and schedules a date for treatment planning.
2. The patient undergoes various imaging procedures, such as magnetic resonance imaging (MRI), and a computerized tomography (CT) simulator is used to determine the location and volume of the tumor within the body. Before imaging, the patient may need to be injected with a contrast agent to enhance the visibility of body tissues and obtain more explicit images.
3. Radiation therapists may mark the patient’s skin to assist with positioning. Some patients may need to wear a plastic mold to immobilize the treatment area. Additionally, technicians may create dental wax or other aids for patients undergoing head and neck treatments to minimize the side effects of radiation on the oral cavity.
4. Based on the imaging data, the oncologist defines the treatment area and the body parts that must be avoided. The radiation therapist then uses a computer to analyze the imaging data and calculate the appropriate distribution of radiation doses to develop the optimal treatment plan.
5. After verifying the treatment plan, the hospital will notify the patient of the first treatment date. Subsequent treatments are typically scheduled five to six times a week, at the same time each day, to allow the body to have a stable rest period for normal cells to recover.
Treatment Techniques
The radiation therapy machines currently used in public and private hospitals in Hong Kong are primarily linear accelerators, which are equipped with various computer devices to enhance the precision of irradiation and minimize side effects. In addition, radiation therapy techniques are constantly evolving to meet the needs of different patients and provide more options.
- Treatment Planning with Plain X-ray Films
This traditional basic radiation therapy technique applies to all cancer sites. Doctors outline the areas of the patient’s body that need to be treated and the areas to avoid irradiation on plain X-ray films. However, since this technique relies on two-dimensional data, doctors often need to enlarge the treatment area to ensure the elimination of all cancer cells, which can result in a more significant impact on normal cells.
- Three-Dimensional Conformal Radiation Therapy (3D-CRT)
This is currently the mainstream therapy and applies to all cancer sites. Doctors use the cross-sectional images obtained from CT scans to assess the radiation area, which can conform to the irregular three-dimensional shape of the tumor. However, if the tumor shape is too irregular or too close to normal organs, avoiding side effects on adjacent tissues may be challenging. If the hospital has the relevant equipment, doctors may arrange for patients to undergo intensity-modulated radiation therapy (IMRT) or other more suitable techniques.
- Intensity-Modulated Radiation Therapy (IMRT)
This technique is suitable for treating nasopharyngeal cancer, prostate cancer, breast cancer, cervical cancer, rectal cancer, and head and neck cancers, especially when the tumor is hidden within normal tissue or close to vital organs. The principle of this technique is to emit radiation beams of different intensities and shapes from various angles, intersecting at the target tumor area to achieve the best therapeutic effect.
- Image-Guided Radiation Therapy (IGRT)
Since the patient’s position may not be the same each time they receive treatment, and the tumor may shrink gradually after treatment, causing movement of the cancer and other organs, the treatment position may need to be continuously adjusted. Doctors will scan the patient before treatment and compare the images with the initial treatment plan to correct discrepancies and adjust the treatment position. This ensures that the radiation beams accurately track the tumor, ensuring that the tumor receives sufficient radiation while avoiding unnecessary damage to normal tissues.
- Respiratory Gating
This technique is mainly applicable to lung cancer, breast cancer, liver cancer, and esophageal cancer. It uses infrared and X-ray technology to detect the body’s movement caused by breathing. The radiation is delivered during a specific phase of the breathing cycle, such as only during exhalation or inhalation, and the beam is turned off the rest of the time to prevent normal tissues outside the tumor area from receiving excess radiation due to breathing movements.
- Arc Therapy
This technique is suitable for treating prostate cancer, endometrial cancer, and head and neck cancers. During treatment, the machine rotates around the patient for one or several circles, and the radiation beam is modulated according to the tumor’s position. This approach delivers a uniform radiation dose to the treatment area while conforming the dose to the tumor’s shape, minimizing the impact on surrounding organs.
- Stereotactic Radiosurgery / X-Knife Radiosurgery
This is typically used to treat malignant and benign brain tumors or certain types of head and neck tumors. The treatment is a collaboration between oncologists, neurosurgeons, and physicists, who use highly accurate positioning instruments to direct radiation beams to a small area, reducing the radiation’s impact on nearby vital organs and normal tissues. The treatment area receives a high dose of radiation in one session to destroy the tumor, similar to the effect of surgical removal. The course of treatment can usually be completed in a single day and is an alternative for patients unsuitable for surgical procedures.
- Stereotactic Radiotherapy / X-Knife Radiotherapy / Body Stereotactic Radiotherapy
Similar to stereotactic radiosurgery or X-knife radiosurgery, the tumor receives a lower dose of radiation per session, and the entire treatment course is longer, ranging from one to three weeks. This technique is often used for small tumors that require high precision in irradiation, such as nasopharyngeal cancer, lung cancer, liver cancer, lymphoma, and spinal tumors.
- Total Body Irradiation
This involves irradiating the entire body with radiation, usually as preparation for the implantation of hematopoietic stem cells or bone marrow. It destroys the patient’s immune system to reduce the risk of rejection and eliminates leukemia cells.
- Intraoperative Radiation Therapy
During tumor removal surgery, a single dose of radiation is administered using a radiation therapy machine to eliminate any cancer cells that may have been missed during the surgery.
- Proton Therapy
Traditional radiation therapy typically uses X-rays, while this technique employs protons [Note 1] as the radiation source. Compared to conventional methods, proton beams release energy only after reaching the tumor area, less impacting surrounding healthy tissues. In addition to common cancers such as lung cancer, liver cancer, and prostate cancer, this method is also applicable to the central nervous system, including the brain and spine, as well as rare cancers such as those in the eye. However, due to its high cost, it is only available in a few private hospitals.
Oral and Injectable Treatments
Internal Radiation Therapy
Internal radiation therapy involves placing radioactive materials directly into or near the tumor within the body and irradiating it at close range. There are typically two methods: using a remote afterloader to insert a sealed radioactive source or using an unsealed radioactive source administered orally or by injection.
- Sealed Radioactive Source
The principle is to place a sealed radioactive source [Note 2] containing a chemical isotope into a small container. After the patient is anesthetized, the radioactive source is implanted into the tumor or nearby body cavity, allowing the source to irradiate the cancer at close range. Sometimes, doctors may use a remote afterloader to handle the radioactive source instead of manual manipulation, reducing the risk of healthcare workers being exposed to radioactive materials. During the procedure, the patient remains while doctors, radiation therapists, and physicists monitor the treatment process to ensure safety. After treatment, the afterloader automatically retracts the radioactive source to its original position, and the doctor will decide whether the patient can go home to rest and resume daily activities based on the situation.
- Unsealed Radioactive Source
The principle is administering soluble unsealed radioactive isotopes through pills, drinks, or intravenous injections, which the patient can take orally or inject into the body. A typical example is iodine, which is used to treat hyperthyroidism and thyroid cancer. For the first four to five days after the patient ingests the iodine, their bodily fluids and excretions will contain trace amounts of radiation. It is advisable to avoid going out unless necessary and to refrain from contact with children or pregnant women. Another common radioactive isotope is strontium, which is used to relieve pain caused by cancer that has spread to the bones and is typically administered through intravenous injection. After treatment, patients can usually go home the same day, although their initial excretions and blood will still contain trace amounts of radiation.
Psychological and Physiological Effects
Side Effects
- Fatigue
During treatment, the body requires a lot of energy to repair damaged normal cells. Additionally, patients often travel to and from the hospital daily for treatment, which can lead to feelings of tiredness and irritability. Patients are advised to take walks or engage in light exercise, avoid alcoholic beverages, and reduce caffeine intake, including tea, coffee, and soft drinks.
- Impact on Blood-Forming Functions
Radiation therapy may affect blood-forming functions, especially when treating large areas such as the chest, abdomen, pelvis, and femur. Patients should avoid crowded places and be cautious when using sharp objects to prevent injury.
- Skin Sensitivity
About three to four weeks into the treatment, patients may experience symptoms such as redness, itching, pain, and skin dryness, similar to sunburn. Generally, these symptoms will gradually subside two to four weeks after the treatment course ends. Patients should not apply ointments or moisturizers alone and should temporarily stop using soap, talcum powder, deodorants, and perfumes.
- Lymphedema
This condition is most commonly seen in breast cancer patients. After the lymph nodes are treated with radiation, lymphatic vessels may become blocked, preventing lymph fluid from circulating normally and causing it to accumulate in the subcutaneous tissue, leading to lymphedema. However, swelling usually appears months to years after treatment, and patients may feel heaviness and swelling in their limbs. At this time, patients should avoid lifting heavy objects, wearing tight clothing, and receiving massages or deep tissue manipulations.
Further Understanding
Read More
Note 1: Protons are components within the atomic nucleus.
Note 2: Isotopes are variants of the same chemical element with the same number of protons but different numbers of neutrons (another type of particle).
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