National Cancer Awareness Day 2025: What is IMRT? Oncologist explains treatment techniques, benefits and risks

IMRT allows doctors to deliver precise radiation doses to tumours while protecting nearby organs and healthy tissue. (Image: Pexels)

Radiation therapy has been a backbone of cancer treatment for decades, but older methods often came at a cost. Healthy tissues could be damaged while tumours were hit, leaving patients to cope with unwanted side effects. Is IMRT, or Intensity-modulated radiation therapy, changing that image?

IMRT allows doctors to deliver higher doses directly to the tumour while limiting radiation to surrounding organs, says Dr Tejinder Kataria, Chairperson, Radiation Oncology, Medanta, Gurugram. "The goal is effective cancer control with fewer side effects, making treatment safer and more precise", he tells Moneycontrol.
Unlike conventional radiation, which treats a broad area, IMRT relies on detailed imaging, computer-guided planning, and fine-tuned delivery. “Every step, from mapping the tumour to daily alignment checks, is designed to maximise accuracy and protect normal tissues.” shares Dr Kataria and explains how IMRT works:

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• Simulation and imaging The process begins with a CT scan — sometimes combined with MRI or PET — while the patient lies still using custom supports. These images map the tumour and surrounding organs, forming the foundation of precision treatment.
• Contouring The tumour and nearby critical organs are outlined on the scans. “This step is vital,” says Dr. Kataria. “It ensures the radiation hits the target while sparing healthy tissue.”
• Inverse planning Clinicians input goals, such as tumour dose and safe limits for organs. Computer algorithms then calculate optimal beam angles and intensity patterns to meet these goals accurately.
• Beam modulation with mlcs Multileaf collimators — hundreds of tiny metal leaves — shape each beam and vary its intensity. Beams can come from fixed angles or rotate continuously, allowing highly conformal treatment.
• Image guidance (IGRT) Daily imaging confirms tumour position and patient alignment. Adjustments compensate for natural organ movement or minor differences in setup, keeping treatment precise.

Here’s what IMRT treats
IMRT is particularly valuable when precision matters:

• Head and neck cancers to protect salivary glands and spinal cord
• Prostate cancer to spare bladder and rectum
• Central nervous system tumours
• Pelvic and gynaecologic malignancies
• Thoracic cancers near the heart and oesophagus
• Certain gastrointestinal, liver, and paediatric tumours

• Benefits Dose can be shaped to maximise tumour control while limiting harm. Organ-sparing reduces long-term side effects, and higher doses can sometimes improve outcomes.
• Potential risks Side effects include fatigue, skin irritation, or site-specific symptoms. Rare late effects may involve organ function changes or low-dose exposure to wider areas. Careful planning minimises these risks.

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Evolving techniques:

Newer methods like VMAT/arc therapy deliver radiation faster with continuous rotation, while adaptive radiation updates plans as anatomy changes. Proton therapy is another option for extreme organ sparing, particularly in children.

FAQs on Radiation Therapy for Cancer Treatment

1. What is radiation therapy?

Radiation therapy is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumours.

2. How does IMRT differ from conventional radiation therapy?

IMRT delivers higher doses directly to the tumour while minimising radiation to surrounding healthy tissues, reducing side effects and improving precision.

3. What types of cancer can IMRT treat?

IMRT is used for head and neck cancers, prostate cancer, central nervous system tumours, pelvic and gynaecologic malignancies, thoracic cancers, and certain gastrointestinal, liver, and paediatric tumours.

4. What are the benefits of IMRT?

IMRT maximises tumour control while limiting harm to healthy tissues, reducing long-term side effects, and sometimes improving outcomes.

5. Are there any risks associated with IMRT?

Potential risks include fatigue, skin irritation, and site-specific symptoms. Rare late effects may involve changes in organ function or low-dose exposure to wider areas. Careful planning helps minimise these risks.

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for specific health diagnosis.