Intensity Modulated Radiotherapy (IMRT)

IMRT- THE BREAKTHROUGH INNOVATION

Towards the end of 20th Century saw the progress in science and technology. With new concept of medical management, scientific knowledge and technology has been applied for diagnosis, treatment and follow-up in every branch of medicine, including oncology.

Cancer screening

Cancer screening which examines the change within molecule level (DNA) will soon be realistic with the help from nanotechnology. The development of surgical oncology, the discovery in new cancer drug for chemotherapy, target therapy and gene therapy, and the invention of equipment for modern radiation therapy are all new hope for the treatment of cancer in the new millennium.

Progress on radiation oncology

The development on imaging technology such as volume-based CT scan, MRI, PET scan or PET/CT scan enable radiation oncologist to know accurate target volume of the cancer in 3-dimension. Together with the progress on software computer planning, medical physicists can now create a 3-dimension treatment plan for cancer patients. Some radiation therapy for clinical practice is shown below:

1. 3D-CRT (3 Dimensions Conformal Radiation Therapy)
2. Stereotactic Radiosurgery
3. Stereotactic Radiation Therapy
4. 3d- Brachytherapy
5. IMRT and 4D-IMRT

IMRT (Intensity Modulated Radiation Therapy)

IMRT is the widely-used radiation therapy in the US. and Europe. It has some special characteristics that are different from the conventional radiation therapy (2-D radiation) as followed:

• Deliver radiation beam precisely to tumor and spare normal tissues.
• Have ability to create multiple targets for radiation and to adjust the intensity of radiation dose to the target
• Advanced computer-controlled treatment plan enable the physicians to calculate the proper amount of radiation for each organs before the treatment. It help them to adjust the maximum radiation dose to cover tumor volume and adjust the radiation to be lower than tolerance dose for normal tissues by using inverse planning system and other tools such as multileaf collimator, wedges, tissue compensators, multiple treatment field and beam energies

IMRT help reducing the use of universal therapy such as conventional 2D-radiation therapy. Physicians can now design treatment plan for each patient (tailor-made or customized or individualized radiation therapy). The benefits of IMRT for clinical uses are as followed:

1. Minimize acute radiation side effects and treatment-related morbidity Because neighboring tissues has very low radiation exposure, side effects rarely occurs and thus help patients continue the treatment until the end while maintaining good quality of life.
2. Decrease acute treatment-related toxicity Even with concurrent chemo-radiation therapy, doctors can still give the radiation dose and chemotherapy dose without worrying about side effects. The overall outcome for both local and systemic control treatment also improves.
3. Improve local tumor control With the new scheme of optimal dose, it will improve local tumor control and thus increase the chance to recover from cancer. Survival rate is higher in many types of cancer such as CNS tumor, head and neck cancer, prostate cancer. There are also reports of improvement on lung, breast, liver, colorectum and gynecologic cancer.
4. Reduce the chance for patients to be admitted to the hospital Patients can be treated as out patient because of lower side effects
5. Reduce the cost of treatment From health economics study in US. , the cost of treatment by IMRT is not higher than the conventional therapy. In some cases, the cost is lower because of shorter treatment time, reduction in admission numbers, and decrease in the need for medicine for side effects
6. Improve quality of life After the treatment, many patients are fully recovered and have no late complications like the conventional therapy. They can go back to work and spend time with their families like they did before.