Radiation Therapy

Overview

Radiation therapy, or radiotherapy, is a common approach in cancer treatment, utilizing high–energy radiation, often in the form of X–rays, to eradicate cancer cells. It can be used alone or combined with other treatments like surgery or chemotherapy.

Radiation oncologists are specialists in this field. They evaluate whether radiation therapy is suitable for a patient and, if so, determine the most suitable type of radiation therapy for the particular type of cancer. Furthermore, they develop a personalized radiation treatment plan, calculating the optimal dosage to destroy cancer cells while minimizing harm to surrounding healthy tissue.

Types of radiation therapy

There are two primary forms of radiation therapy: External Beam Radiation Therapy (EBRT) and internal radiation therapy. Both modalities operate by destroying the DNA of cancer cells. When lacking DNA instructions directing growth and proliferation, cancer cells die, leading to the shrinkage of tumors.

External Beam Radiation Therapy (EBRT)

EBRT stands as the most prevalent form of radiotherapy. In EBRT, a machine directs beams of high–energy radiation, which can be X–rays (most commonly), electrons, or protons, towards the tumor. Precision is crucial in EBRT, and your radiation oncologist will devise a treatment plan to focus radiation on the tumor while safeguarding healthy tissue.

Various forms of EBRT include:

• 3D conformal radiation therapy, utilizing CT scans and computer software to generate a 3D tumor model. The machine then directs radiation beams precisely at the cancer site, sparing healthy tissue.
• Intensity–Modulated Radiation Therapy (IMRT), an advanced form of radiation therapy employing multiple radiation beams with varying dose intensities. It delivers a higher radiation dose to the tumor while minimizing doses to healthy tissue.
• Arc–based radiotherapy, a type of IMRT directing energy beams of varying intensity in a rotational arc–like pattern. This method is faster than traditional IMRT, with Volumetric Modulated Arc Therapy (VMAT) and tomotherapy being specific forms.
• Image–guided radiotherapy (IGRT), an EBRT type, where the radiation machine captures a low–dose X–ray or mini CT scan before each treatment. This aids in aligning the treatment site, enhancing precision in radiation delivery.
• Particle therapy, utilizing protons instead of photons (X–rays) for radiation. Protons can provide the same radiation dose to the tumor while reducing exposure to healthy tissues.
• Stereotactic radiosurgery, such as Gamma knife surgery, utilizing focused, high–dose radiation to eradicate small brain tumors with surgical precision without the need for actual surgery. Typically completed in one to five days.
• Stereotactic Body Radiation Therapy (SBRT), administering high doses of focused radiation to eliminate tumors outside the brain with surgical precision, without actual surgery.
• Intraoperative Radiation (IORT), delivering radiation during surgery to destroy any remaining cancer cells post–surgical removal of a tumor. IORT eradicates any residual cancer cells deemed unsafe for surgical extraction.

Internal radiation therapy

Internal radiation therapy involves placing radiation within your body, in close proximity to cancer cells, and is particularly effective for treating smaller tumors in areas such as the head, neck, breast, cervix, uterus, or prostate.

Internal radiation can be administered through a solid source or in liquid form:

• Brachytherapy utilizes a solid radioactive source, known as a “seed,” implanted inside or beside a tumor. This source releases radiation to a localized area, effectively targeting and eliminating cancer cells. 

Some brachytherapy implants release low doses over an extended period (weeks), while others release higher doses over shorter durations (minutes). Certain implants used in brachytherapy are temporary, while others remain in the body permanently, ceasing radiation release over time.

• Systemic therapy introduces liquid radioactive material into your bloodstream to locate and eradicate cancer cells. Some forms of systemic therapy involve swallowing the substance, while others are administered through a vein via injection (IV). 

Radionuclide therapy, a type of systemic therapy, includes radioimmunotherapy where a radioactive protein identifies specific cancer cells, attaches to them, and subsequently releases radiation to eliminate them.

Reasons for undergoing the procedure

Radiation therapy serves to eliminate cancer cells, reduce tumor size, and alleviate cancer symptoms. It can be employed as the sole treatment or utilized to:

• Reduce tumor size prior to other cancer treatments, such as surgery (neo–adjuvant therapy).
• Eradicate any residual cancer cells following surgery (adjuvant therapy).
• Eliminate cancer cells that reappear after previous treatment.
• Additionally, radiation therapy can target and eliminate benign (noncancerous) tumors causing symptoms.

Risks

Many patients undergo radiation therapy across multiple treatment sessions to prevent administering the full dose all at once. This staggered treatment schedule permits healthy tissue to recover between sessions, thereby reducing side effects.

However, despite these precautions, individuals may still experience unpleasant side effects, primarily affecting the area undergoing direct radiation. Your radiation oncologist will aid in managing these side effects, which may include:

• Headaches
• Skin irritation
• Dry, itchy scalp
• Hair loss
• Fatigue
• Nausea
• Vomiting
• Diarrhea
• Mouth sores
• Painful swallowing
• Reduced appetite
• Burning sensation in the throat or chest
• Frequent urination in small amounts
• Pain or burning during urination
• Abdominal bloating or cramps
• Urgency for bowel movements

Consult with your radiation oncologist to understand the expected side effects based on the recommended radiation therapy for your specific cancer type.

While radiation therapy is a successful treatment for various cancers, it could elevate the risk of developing another type of cancer in the future. For many individuals, the advantages of radiation therapy outweigh the potential risks. It’s essential to discuss and evaluate the benefits of treatment in comparison to potential risks with your radiation oncologist.

Before the procedure

In preparation for internal radiation therapy, you may undergo a physical examination and imaging. Your radiation oncologist will give you specific instructions on how to prepare for the procedure, customized to the type of radiation delivery method.

For External Beam Radiation Therapy (EBRT), a planning appointment called simulation is conducted. Simulation is a vital step in treatment planning that customizes the approach to your individual needs.

During simulation:

• Positioning: You are placed on a table in the exact position you will be during treatment sessions. A mold or mask may be used to secure your body in place, ensuring correct alignment. Temporary or permanent markings (tiny dots) may be applied to indicate which body parts will receive the radiation.
• Scans: You undergo a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI) to precisely visualize the tumor’s location. This imaging data aids your care team in customizing X–rays to target the tumor while minimizing exposure to healthy tissue.

Simulation enables your radiation oncologist to determine the appropriate radiation dosage and delivery method for your treatment.

During the procedure

Internal radiation therapy typically takes place in an outpatient treatment room or within a hospital setting. Your radiation oncologist may introduce the radiation implant using a small, flexible tube known as a catheter. Anesthesia is administered for this treatment to ensure you experience no pain or discomfort throughout the procedure. In the case of systemic internal radiation therapy, radioactive fluid is delivered through an IV.

During EBRT, you lie on a table in a position akin to the simulation process. The radiation machine orbits around you without direct contact. A radiation therapist, located in a separate room, operates the machine and maintains communication with you through an intercom. The machine precisely administers radiation doses to the tumor, adjusting its position as needed. Throughout the treatment, you will not experience any sensation.

After the procedure

After internal radiation therapy, you typically return home after a brief recovery on the same day. In some instances, a hospital stay may be necessary until your body eliminates residual radiation. Following systemic (IV) radiation therapy, minimal amounts of radiation may be discharged through bodily fluids such as sweat, urine, and blood. For those undergoing IV or permanent internal radiation therapy, there is a slight risk of radiation exposure to others. It is crucial to adhere to the guidance provided by your radiation therapy team regarding the level of contact you should maintain with others post–radiotherapy.

Both before and after EBRT, you should be able to resume your regular daily activities without any risk of exposing others to radiation.

Outcome

While some patients undergoing radiation therapy can continue their normal routines without difficulty, others may experience discomfort and need time off for rest. Side effects might not become apparent until several weeks into treatment when a greater number of cells are affected.

It’s recommended to have a discussion with your radiation care provider about both the optimal and worst–case scenarios as you organize your schedule around the treatment.