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How Radiotherapy( or radiation therapy) Works!
06, Oct, 2024

How Radiotherapy Works

Radiotherapy (or radiation therapy) is a medical treatment that uses high doses of ionizing radiation to kill cancer cells or shrink tumors. The radiation damages the DNA inside cells, which disrupts their ability to divide and grow. While radiation affects both cancerous and healthy cells, cancer cells are more vulnerable because they reproduce more rapidly and are less able to repair DNA damage.

Key Concepts of How Radiotherapy Works:

1. Ionizing Radiation

Radiotherapy uses high-energy radiation, such as X-rays, gamma rays, or particle beams (e.g., protons, electrons), to destroy cancer cells. This radiation can break chemical bonds in DNA, leading to cell death.

2. DNA Damage

The radiation damages the DNA in the cancer cells directly or indirectly. Indirect damage occurs when radiation ionizes water molecules in the cell, creating free radicals that damage the DNA. Damaged DNA causes the cancer cells to stop dividing and ultimately die.

3. Targeting Cancer Cells

Radiotherapy is carefully targeted to maximize the dose to the cancer while minimizing exposure to surrounding healthy tissue. The goal is to destroy cancer cells while sparing as many normal cells as possible. Advances in imaging and computer technology have improved the precision of radiation targeting.

4. Fractionated Treatment

Radiation is typically delivered in smaller doses over a series of treatment sessions. This approach, called fractionation, allows healthy cells time to recover between treatments while increasing the cumulative damage to cancer cells. It also reduces side effects.

5. Different Types of Radiotherapy

  • External Beam Radiation Therapy (EBRT): This is the most common form of radiotherapy, where a machine outside the body directs radiation beams at the tumor. Modern techniques like IMRT (Intensity-Modulated Radiation Therapy) and IGRT (Image-Guided Radiation Therapy) enhance precision.
  • Internal Radiation Therapy (Brachytherapy): In brachytherapy, a radioactive source is placed inside or very close to the tumor. This delivers a high radiation dose to the tumor while sparing nearby tissues.
  • Systemic Radiation Therapy: In this type, radioactive substances are swallowed or injected, allowing the radiation to travel throughout the body (e.g., radioactive iodine treatment for thyroid cancer).

6. Effect on Cancer Cells

Cancer cells are more sensitive to radiation because they divide more rapidly and have fewer mechanisms to repair DNA damage. When radiation damages the DNA of cancer cells, they lose their ability to reproduce, and over time, they die off. This helps shrink the tumor or eliminate cancer cells.

7. Effect on Normal Cells

Healthy cells that are exposed to radiation can also be damaged, but they tend to recover better than cancer cells. Treatment planning is designed to minimize radiation exposure to healthy tissues, but side effects can still occur depending on the area being treated.

How Radiotherapy is Delivered:

Planning Stage

Before starting radiotherapy, a planning process called "simulation" is conducted. It involves imaging techniques (CT scans, MRIs) to precisely locate the tumor and design a personalized treatment plan.

Treatment Sessions

For external beam therapy, patients usually receive radiation for a few minutes per session, and treatments are typically scheduled 5 days a week for several weeks. Each session is quick, but careful alignment ensures accuracy.

Side Effects of Radiotherapy:

Side effects vary depending on the area being treated and the dose. Common side effects may include fatigue, skin irritation, hair loss (in the treated area), and localized symptoms like digestive or urinary problems.

Most side effects are temporary, but some long-term side effects can occur, such as fibrosis (scarring) or damage to tissues near the treatment site. Modern techniques aim to minimize these risks.

Conclusion:

Radiotherapy works by damaging the DNA of cancer cells, preventing them from dividing and growing. It is often used in conjunction with surgery or chemotherapy and is effective for many types of cancer. Despite some side effects, radiotherapy is a powerful tool for shrinking tumors and controlling cancer growth.

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