Deep Radiation Therapy – Radiotherapy Explained

What is Deep Radiation Therapy?

Deep radiation therapy is a medical procedure within the field of radiotherapy (also known as radiation oncology), in which ionizing radiation is precisely directed to treat tumors or diseased tissue located deep inside the body. Unlike surface radiation, which targets skin conditions or superficial structures, deep radiation therapy penetrates far into the body to deliver its therapeutic effect at the target site.

The procedure is primarily used in oncology (cancer medicine) but can also be applied to benign conditions. Together with surgery and chemotherapy, deep radiation therapy is one of the three main pillars of modern cancer treatment.

Mechanism of Action

In deep radiation therapy, high-energy ionizing radiation – most commonly in the form of photons (X-rays or gamma rays) or particle beams (e.g., protons or electrons) – is directed at the tumor. This radiation damages the DNA of tumor cells, preventing them from dividing and causing them to die.

Because tumor cells generally divide faster than healthy cells and often have less effective DNA repair mechanisms, they are more sensitive to radiation. Through careful planning and beam alignment, the aim is to minimize exposure to the surrounding healthy tissue as much as possible.

Technical Methods of Deep Radiation Therapy

External Beam Radiation Therapy (EBRT)

The most common form of deep radiation therapy is delivered from outside the body: a linear accelerator generates high-energy X-rays that are directed at the tumor from multiple angles. Modern techniques include:

• 3D Conformal Radiation Therapy (3D-CRT): Radiation fields are shaped three-dimensionally to match the contours of the tumor.
• Intensity-Modulated Radiation Therapy (IMRT): The intensity of radiation within each field is varied to maximize tumor dose while sparing adjacent organs.
• Image-Guided Radiation Therapy (IGRT): Imaging techniques are used during treatment to verify the exact position of the tumor.
• Stereotactic Body Radiation Therapy (SBRT/SABR): Highly precise, high-dose radiation delivered in a small number of sessions, particularly suited for small, well-defined tumors.
• Proton Therapy: Uses proton beams that deposit maximum energy directly in the tumor (Bragg peak), significantly sparing tissue beyond the target.

Internal Radiation Therapy (Brachytherapy)

Brachytherapy involves placing radioactive sources directly inside or immediately adjacent to the tumor. This allows for a very high local radiation dose with minimal impact on surrounding healthy tissue. Common applications include prostate, cervical, and breast cancer.

Clinical Applications

Deep radiation therapy is used across a wide range of conditions:

• Malignant tumors: including lung, prostate, breast, colorectal, bladder, cervical, head and neck, and brain tumors
• Curative intent: Aiming for complete elimination of all tumor cells
• Adjuvant therapy: Post-surgical radiation to eliminate residual cancer cells
• Neoadjuvant therapy: Pre-surgical radiation to reduce tumor size
• Palliative therapy: Relieving symptoms (e.g., pain from bone metastases) without curative intent
• Benign conditions: e.g., keloid scars, Dupuytren's contracture, or inflammatory joint diseases

Treatment Process

Before deep radiation therapy begins, a detailed treatment planning process takes place. CT, MRI, or PET-CT scans are used to create precise images of the tumor and surrounding structures. Based on these images, medical physicists and radiation oncologists calculate the optimal treatment plan.

Radiation is typically delivered in multiple fractions (individual sessions) spread over several weeks. This approach – known as fractionated radiotherapy – allows healthy tissue to recover between sessions, while tumor cells accumulate cumulative damage. A standard course of treatment often involves 25–35 sessions, usually given daily on weekdays (Monday to Friday).

Side Effects

Like all medical treatments, deep radiation therapy can cause side effects, which vary depending on the region being treated, the total dose, and the individual patient.

Acute Side Effects (during or shortly after treatment)

• Tiredness and general exhaustion (fatigue)
• Skin reactions in the treatment area (redness, dryness)
• Mucositis (inflammation of mucous membranes, e.g., in the mouth and throat during head and neck radiation)
• Nausea and digestive problems (with abdominal radiation)
• Hair loss in the irradiated field

Late Side Effects (weeks to years after treatment)

• Fibrosis (hardening) of irradiated tissue
• Lymphedema (swelling caused by impaired lymph drainage)
• Organ-specific damage (e.g., pulmonary fibrosis, bowel problems, cardiac effects)
• Very rarely: radiation-induced secondary tumors

Advantages of Deep Radiation Therapy

• Non-invasive – no surgery required
• Highly targeted with modern precision techniques
• Can be combined with other therapies (chemotherapy, immunotherapy)
• Effective as a standalone curative treatment for certain tumor types
• Usually performed on an outpatient basis

References

1. Perez CA, Brady LW, Halperin EC: Principles and Practice of Radiation Oncology. 6th ed. Lippincott Williams and Wilkins, 2013.
2. World Health Organization (WHO): Cancer – Radiotherapy. www.who.int/health-topics/cancer (2023)
3. Baskar R, Lee KA, Yeo R, Yeoh KW: Cancer and Radiation Therapy: Current Advances and Future Directions. International Journal of Medical Sciences, 2012; 9(3):193–199.