How Radiation Therapy Works to Destroy Cancer Cells

Understanding Radiation Therapy

A cancer diagnosis can be overwhelming, and understanding your treatment options is an important first step. Radiation therapy (also called radiotherapy) is one of the most effective and widely used treatments for cancer. Nearly half of all people diagnosed with cancer receive radiation therapy at some point during their treatment journey.

Radiation therapy uses high-energy radiation, most commonly X-rays, to destroy cancer cells while preserving as much healthy tissue as possible. Depending on the type and stage of cancer, it may be used alone or in combination with surgery, chemotherapy, targeted therapy, or immunotherapy.

With advances in technology, modern radiation therapy has become highly precise, allowing doctors to treat tumours accurately while reducing side effects and improving treatment outcomes.

How Does Radiation Therapy Destroy Cancer Cells?

Every cell in the body contains DNA, which controls how it grows and divides. Cancer develops when abnormal cells begin multiplying uncontrollably.

Radiation therapy works by damaging the DNA inside cancer cells. Unlike healthy cells, cancer cells have a much lower ability to repair this damage. As a result, they gradually lose their ability to grow, divide, and survive.

Here's how the treatment works:

• High-energy radiation beams are precisely directed at the tumour.
• The radiation damages the DNA of cancer cells.
• Cancer cells stop growing and dividing.
• Over time, the damaged cancer cells die naturally.
• The body's immune system gradually clears away these dead cells.

It is important to understand that radiation therapy does not kill all cancer cells instantly. The effects continue even after treatment sessions are completed, and cancer cells may continue to die over several weeks.

Modern radiation therapy techniques use advanced imaging and computer-guided planning to deliver radiation with exceptional precision, minimizing exposure to surrounding healthy tissues.

Types of Radiation Therapy

Radiation therapy can be delivered in different ways depending on the type, size, and location of the cancer.

External Beam Radiation Therapy (EBRT)

External Beam Radiation Therapy is the most common form of radiation treatment.

A machine called a linear accelerator (LINAC) delivers high-energy radiation beams from outside the body directly to the tumour. Treatment is carefully planned using CT, MRI, or PET scans to ensure the radiation reaches the cancer accurately while sparing nearby healthy organs.

Patients do not become radioactive after external beam radiation therapy and can safely interact with family members, including children and pregnant women.

Internal Radiation Therapy (Brachytherapy)

Brachytherapy involves placing a radioactive source directly inside or very close to the tumour. Because the radiation is delivered from within the body, higher doses can be given to the cancer while reducing exposure to surrounding tissues.

Brachytherapy is commonly used for cancers of the:

• Cervix
• Endometrium (uterus)
• Prostate
• Breast
• Head and neck
• Eye

Systemic Radiation Therapy

Some cancers are treated with radioactive medicines that are swallowed or given through an intravenous injection. These medicines travel through the bloodstream and selectively target cancer cells.

One of the best-known examples is radioactive iodine therapy, which is commonly used to treat certain types of thyroid cancer.

When Is Radiation Therapy Recommended?

Radiation therapy may be used at different stages of cancer treatment to achieve different goals.
Your radiation oncologist may recommend it to:

• Cure cancer by destroying all cancer cells

• Shrink a tumour before surgery

• Eliminate microscopic cancer cells remaining after surgery

• Relieve symptoms such as pain, bleeding, or pressure caused by advanced cancers (palliative radiation therapy)

• Reduce the risk of cancer recurrence

Every treatment plan is individualized based on the patient's cancer type, stage, overall health, and treatment goals.

Benefits of Radiation Therapy

Radiation therapy remains one of the most effective cancer treatments because it offers several important advantages.

Highly Precise Treatment

Advanced imaging and treatment planning enable radiation to target tumours accurately while minimizing damage to healthy tissues.

Non-Invasive
Unlike surgery, radiation therapy does not involve cuts or incisions, making it a less invasive treatment option with no surgical recovery time.

Improved Cancer Control
Radiation therapy plays a key role in reducing tumour growth, lowering the risk of recurrence, and improving long-term survival for many cancers.

Symptom Relief
Even when cancer cannot be completely cured, radiation therapy can effectively relieve pain, bleeding, difficulty swallowing, or pressure caused by tumours, improving  quality of life.

Works along with Other Treatment modalities

Radiation therapy is often combined with surgery, chemotherapy, immunotherapy, hormonal therapy, or targeted therapy as part of a comprehensive cancer treatment plan.

Which Cancers Can Be Treated with Radiation Therapy?

Radiation therapy is commonly used to treat:

• Breast cancer
• Cervical cancer

Many non cancerous conditions can be effectively treated with radiation therapy: 

• Prostate cancer
• Lung cancer
• Brain tumours
• Head and neck cancers
• Rectal cancer
• Skin cancer
• Lymphomas
• Bone cancers
• Thyroid cancer

Many childhood cancers

• Keloids (after surgical excision) 
• Arteriovenous malformations (AVMs) 
• Acoustic neuromas (Vestibular schwannomas) 
• Meningiomas 
• Pituitary adenomas 
• Trigeminal neuralgia

Cancer Care at STAR Hospitals

At STAR Hospitals, we combine advanced technology with expert clinical care to deliver personalized radiation oncology services.

Our radiation oncology department is equipped with the region's first TrueBeam STx Linear Accelerator with HyperArc technology, enabling highly precise treatments for both common and complex cancers. AI-enabled treatment planning, image-guided radiation therapy (IGRT), and multidisciplinary Tumor Board discussions ensure that every patient receives an individualized treatment plan based on the latest evidence and international treatment guidelines.

If you or a loved one has been diagnosed with cancer, consulting a radiation oncologist early can help you understand all available treatment options. Early diagnosis, timely intervention, and expert-led care can significantly improve treatment outcomes and quality of life.

Book an appointment with our oncology specialists today to learn more about personalized radiation therapy at STAR Hospitals.