Radiation Therapy: A Guide to Intensity-Modulated Radiation Therapy and the Latest Technology

Pushing for the right radiation therapy treatment

Advances in radiation therapy offer many new treatment choices. When a patient's oncologist recommends radiation, be sure to check into whether the type of radiation the doctor suggests is the most advanced strategy available for his cancer.

Of course, you're naturally going to have many questions. Among them will be concerns about whether the type of radiation the doctor's recommending is the most advanced and aggressive strategy available for the particular type of cancer.

"Not all radiation therapy is created equal" says oncologist Shalom Kalnicki, chairman of radiation oncology at Montefiore Medical Center and the Albert Einstein College of Medicine in New York. "You want to understand what's involved and find out about all the options so you can make the best choice."

For suggestions on what to ask during this important discussion, see 15 Questions to Ask About Radiation Therapy for Breast Cancer . Certainly, the oncologist knows more about cancer than you do and may have solid reasons for recommending a particular treatment -- but it's also possible he's recommending only the treatment available in the hospitals he's affiliated with. To prepare for this talk, you'll want to know the terms for the wide variety of techniques available. Here's a rundown of the newest radiation technologies:

3D-CRT, IMRT, and IG-IMRT (or IGRT) Explained

3-D conformal radiation therapy (3D-CRT)

Probably the most common form of standard radiation used today is conformal radiation, in which doctors use computer technology to map the tumor with imaging techniques such as MRIs and P ET scans. This allows doctors to target the radiation beam to more closely match the shape of the tumor. Scans cover the tumor's width, height, and depth -- hence the term 3-D.

IMRT (intensity-modulated radiation therapy)

IMRT has gradually become the standard of care for certain types of cancers, particularly cancers of the head and neck, lung, abdomen, and pelvis, for which precision in delivering radiation is important. It's also starting to be used in breast and prostate cancer treatment . Here are some basics to know about IMRT:

  • It delivers precise, strong radiation. IMRT uses a linear accelerator to deliver thousands of precisely focused small beams of radiation that follow the exact contours of a tumor, allowing the radiation oncologist to target the tumor much more exactly while damaging less of the surrounding tissue. Because surrounding tissue is better protected, the radiation dosages delivered via IMRT can also be higher, resulting in more effective treatment.

"We compared treatment techniques for cancers of the lung, pelvis, abdomen, and head and neck and showed that IMRT was much more effective, and resulted in fewer side effects, than conventional radiation therapy," says Kalnicki, who presented these findings to the American Society for Therapeutic Radiology and Oncology in October 2007.

  • It's not available everywhere. Unfortunately, because it uses different equipment than standard radiation therapy, IMRT is not available in all hospitals. If you and the person you're caring for ultimately decide that this is the treatment she wants, she may have to ask her doctor whether she should seek treatment at another hospital or cancer center. It may be worth fighting for, however, as the studies are impressive, and many experts advocate a switch to IMRT for the treatment of many more types of cancer. For example, one recent study of IMRT for prostate cancer -- one of the types of cancer IMRT is not typically used for -- showed that the ability to use higher doses of radiation more than doubled the rate of local tumor control from 43 to 94 percent and reduced the rate of normal tissue damage from 10 to 2 percent.

Image-guided IMRT (IG-IMRT, or IGRT)

  • It delivers more easily adjusted radiation. This even more advanced form of IMRT uses online computer imaging to adapt radiation therapy to the changing contours of a tumor in real time during the radiation therapy itself. (In regular IMRT, the mapping is usually done ahead of time.) The computer compares images taken before the procedure to those taken during the procedure itself. Since tumors typically shrink as a result of radiation therapy, IG-IMRT (also called IGRT) allows doctors to adjust the radiation to accommodate the shrinking tumor margins, protecting the growing area of healthy tissue around the edge.
  • It's good for delicate locations. Also called image-guided adoptive planning, IG-IMRT has been used with great effectiveness to treat tumors in delicate, complex locations such as the head and neck. Study results show that IG-IMRT allows doctors to use high doses of radiation with less damage to healthy tissue.

Respiratory Gated Radiation Therapy Explained

Helical tomotherapy

Another type of IMRT, this technique uses a large linear accelerator inside a doughnut-shaped contraption that spirals around a patient's body during treatment, delivering beams of radiation from many angles. Advocates believe this technique, also called a spiral CT scan, allows even more precisely focused radiation. It's also sometimes used as a screening technique as well.

Respiratory gated radiation therapy

Because radiation therapy requires such precise targeting, even the tiny movements caused by breathing, swallowing, and blood flow can throw off the radiation beams and lead to tissue damage. To solve this problem, respiratory gated treatment employs computer imaging to map radiation treatment so that the dose of radiation is modified to accommodate changes in the shape of the tumor caused by the patient's breathing or swallowing. (Without respiratory gating, doctors typically radiate the entire area that the tumor moves through as the patient breathes, which causes radiation to be delivered to healthy tissue.)

Sometimes called target motion management, this brand-new therapy increases the success of treatment for tumors in the lung, in the breast near the lung or heart, or in the neck or thyroid.

Stereotactic radiosurgery

Used almost exclusively for brain tumors, this technique aims a very high-dose radiation beam at a small area during a single session. It's the dramatic procedure you see on hospital shows during which the patient's head is enclosed inside a frame to hold it still. A related technique, stereotactic radiotherapy, uses smaller, fractional doses of radiation given multiple times. It's being studied for potential use on tumors in the lung as well as in the head.

Melanie Haiken

Melanie Haiken discovered how important it is to provide accurate, targeted, usable health information to people facing difficult decisions when she was health editor of Parenting magazine. See full bio

almost 7 years, said...

I had breast cancer and tumor removed from one breast. Howvever, because I went online to research radiation, I found there is a new procedure for radiation after surgery called "mammasite", This involves the surgeon during surgery to remove tumer, to implant a bulb apparatus inside the breast and having wires, protrubing out by your breast. Not everyone can qualify it depends on location of the tumor. What is great is that you only have radiation for five day twice a day. The radiation machine or whatever is attached to these tubes which were implanted inside your breast. I had no pain just a little discomfort and I had a wonderful doctor, surgeon and radiation center staff who provided me with the care above and beyond what I expected to have. They knew I wanted to go home for thanksgiving and the radiation staff finished my last treatment at five am in the morning so I go home for the holiday. Also, the removal of this implant did not hurt at all. Would I go through this again, yes definitely would. I was so worried for weeks thinking about going through surgery and radiation and if you have the right doctors and radiation center like I had, you are home free. God bless all of them who took care of me. Ladies, do your homework like I did and research all your options with your doctor and wherever information is available and then decide whats best for you. My first surgeon who must of been loco, told me I had only two options remove lump or breast and five to six weeks of radiation and let him know. I went to cancer close to home, but they wanted 7000 dollars first because my insurance was not in their network. Then I said goodbye to this doctor and cancer center and God directedme to this wonderful cancer center which was farther away and covered under my insurance. However, I would of gone to China if I had to. Anyway, there was ahospitality place we stayed in during testing, surgery and radiation. My advice its your body and make sure your surgeon and radiation center is okay. Check everything out and take control.