Intensity-modulated radiotherapy (IMRT) is an advanced type of radiation therapy.

This therapy works by delivering radiation faster and with improved precision than what's possible with conventional radiation treatment. IMRT isn't appropriate in every situation. It's usually an option for patients with cancer affecting organs, tissues, or glands in the urinary system.

  • As is the case with traditional radiation therapy, IMRT may be done post-surgery or in lieu of surgery if it's not possible to operate.
  • It might also be recommended if a tumor is small and localized.

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What Is Intensity-Modulated Radiation Therapy?

IMRT is a type of radiation therapy that works with advanced software and a computer-controlled device called a medical linear accelerator (LINAC). Radiation is delivered in a way that matches the shape and size of the tumor based on a 3D image that's created. If, for instance, a patient has prostate cancer, the high-energy beams would target the affected part of this gland in a way that minimizes exposure risk to healthy tissues in the prostate and nearby structures.

What Are Pre-Treatment Sessions?

Some patients have a simulation or pre-treatment session before beginning regular treatments. The purpose of doing this is to localize the cancer as much as possible. Doing so can also further reduce the risk of radiation exposure and improve the odds of seeing successful results with IMRT.


How Are Sessions Planned?

Treatment is carefully planned based on several pre-treatment steps. A urological surgeon often performs tests prior to IMRT to determine the extent of the cancer and the exact size and location of the tumor. This is usually done with CT and MRI scans. Computerized dose calculations are made based on the tumor's dimensions. Since radiation is delivered from different directions, higher does can be safely administered in a way that minimizes potential side effects.

What Happens During IMRT?

During sessions, the patient rests on a specialized table. The LINAC device rotates around the patient. It administers the beams that penetrate the patient's body to target the tumor from multiple directions in a single rotation. Colored ink is sometimes used to mark the skin in the affected area to further increase the accuracy of radiation delivery.

Molded devices may be used to help the patient remain in the correct position. Adjustments to how beams are delivered can be made as the tumor shrinks with each subsequent session. Treatment usually lasts about 15 to 30 minutes per session. IMRT is often scheduled five or seven days per week.

While noises and odors from the machine may be noticed during sessions, patients typically do not feel any pain as the radiation is delivered with the rotating device. However, the machine can be stopped at any time during a session if there is any discomfort experienced.

Because intensity-modulated radiotherapy offers greater accuracy with shorter sessions, it may be an option for patients who've already reached the maximum dosage limit with traditional radiation therapy. IMRT may also benefit patients who've experienced a recurrence of urinary cancer that was previously treated with surgery. Results will vary based on underlying health and other factors. However, many patients tolerate IMRT well. Also, potential risks are typically less than what's associated with chemotherapy and traditional radiation therapy. There is a slight risk that cancer may develop with any type of radiation treatment. For this reason, a urologist usually recommends periodic screenings.

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Thomas E. Ahlering, M.D.
Urological Cancers
Professor and Vice Chairman
Greg E. Gin, M.D.
Urologic Oncology, Minimally Invasive Surgery
HS Assistant Clinical Professor
Cory M. Hugen, M.D.
Urological Cancers
HS Assistant Clinical Professor
Edward Uchio, M.D., F.A.C.S., C.P.I.
Urological Cancers
Mark Jordan, M.D., F.A.C.S., F.R.C.S. (C)
Urological Cancers
Residency Program Director, HS Clinical Professor

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