Intensity modulated radiation therapy (IMRT) is well on its way to becoming the new gold standard for treating cancer, especially head and neck and genitourinary tumors. The ability to shield noncancerous areas while sending higher doses of radiation allows for fewer negative side effects and better cure rates.
Arno Mundt, MD, professor and chairman of the radiation and oncology department at the University of California at San Diego has led several studies about the technology. In one, IMRT users were asked about their impressions of the technology and their rate of use for various conditions.
The first patient treated via IMRT was in 1992. Acquisition has been rapid, with 74 percent of the country using IMRT by 2004, according to Mundt’s use study. That’s a complete revolution, he says. “You don’t see a complete change in the field that quickly. We did things very similarly for over 100 years. There were improvements, but the basic approach was very static until IMRT. This is a very exciting time.”
Improving quality of life
Head, neck, and prostate cancers are the most common conditions treated with IMRT and the most likely to benefit from the ability to increase radiation to the tumor while protecting healthy tissue. IMRT has revolutionized treatment of head and neck cancer, says Charles H. Albrecht, MD, of Finger Lakes Radiation Oncology Center in Clifton Springs, N.Y., which began using IMRT in 2000. For these patients, radiation has a drastic quality-of-life effect on the carotid salivary glands. “In conventional radiation, the patient would get at least the same dose to the salivary glands if not a higher dose,” Albrecht says. They had to always carry a water bottle with them, and the lack of saliva has serious consequences — such as teeth falling out or rotting and terrible dry mouth. Now, few patients need a water bottle.
When treating with conventional radiation, the patient typically receives 300 rads a minute. That’s concentrated and over very quickly, Albrecht says. With IMRT, only 75 to 150 rads hit the patient, and the rest is absorbed into the equipment. “It takes longer to give the same dose of radiation, but we’re doing it more precisely.”
Despite these improvements, IMRT still is probably the scariest thing a patient will go through, says Albrecht. The mouth, larynx, and other elements exposed to even the lower dose of radiation become inflamed. “But coming out of it, recovery is faster and we’re able to spare more normal functions.”
Albrecht uses equipment from NOMOS Radiation Oncology, which is essentially an attachment to a standard linear accelerator. Albrecht “like[s] that you’re using a very mature technology producing radiation. The accelerator is basically technology introduced in the late 1950s that has matured and is very reliable.”
After a planning CT scan, Albrecht traces on the computer screen the carotid glands, submandibular glands, and all the lymph nodes and the tumor structure he wants to treat. This goes back to the physicist who comes up with a treatment plan that delivers the right dose to each structure. In the case of tonsil tumors, Albrecht can attack the tonsil and the lymph node under the jaw bone aggressively but send a different dose of radiation to other lymph nodes that may or may not be cancerous. “We are definitely increasing our chances of a cure,” he says. “I’ve been very impressed with it clinically.”
First timers blown away
There is little doubt that IMRT lives up to the great reviews. When Ironwood Cancer & Research Center in Chandler, Ariz., opened last October intending to offer state-of-the-art radiation and medical oncology services, says Brent Applegate, chief therapist, the facility installed IMRT equipment from Elekta.
The facility’s first IMRT patient had pancreatic cancer. Because of the anatomy of the pancreas and the organs around it, most people with pancreatic tumors don’t perform very well, Applegate says. It was difficult to give a high enough dose to treat the tumor without making them sick. “We gave her a fairly escalated dose, and she had little or no side effects, which is unheard of. We were blown away for our first experience out of the gate.” He says they kept waiting for the patient to get sick, but she came back, smiling, every day. “That really sold us on the technology,” Applegate says.
The good results kept coming. The facility’s staff was able to get patients through treatments for five to seven weeks without breaks. That results in a better outcome “because we can attack the tumor on a daily basis. We don’t need to back off” and give patients a chance to recover from the side effects that usually come with radiation therapy.
And Ironwood hasn’t backed off. In fact, the organization operates from 5am to 8pm. “We’re so busy that we’re struggling with staffing.” Two therapists are assigned to each linear accelerator, and one or two physicists per department handle the quality assurance process. Meanwhile, dosimetrists take the CT data set and create a three-dimensional treatment plan on a CAD system. The process takes about a week and a half from CT to treatment.
Ironwood is a clinical visit site for Elekta, hosting two or three groups a month. “Local docs call all the time kicking around the idea,” Applegate says. “We have a revolving door. People are impressed with what we’ve got going on here.”
Albrecht, who uses serial tomotherapy from NOMOS, explains that during treatment, the whole machine revolves around the patient, with radiation hitting 4 centimeter strips. The equipment keeps moving 4 centimeters. Other tomotherapy moves the radiation sources continuously, which is “very nice and elegant but inherently more complicated.” In that case, “we’re trying to produce a radiation source that’s moving at the same time rather than holding the source in one plane and controlling the effective output by using shutters and blocks to very carefully control how much of it gets through to the patient.”
Mundt, who uses SmartBeam IMRT from Varian, says image-guided radiation therapy (IGRT) allows radiation oncologists to take images of the patient, often daily, so the treatment plan can be modified as necessary. If the patient has lost weight, that can affect treatment. Other subtle changes mean the physician has to compensate for movement and location. For example, when treating a prostate cancer patient, the amount of gas in the rectum can move the prostate a fraction of a centimeter. But that’s enough to throw the treatment plan off kilter. “IGRT can tell you where the prostate is every day,” says Mundt. “The ideal is to mate the two together and have IG-IMRT—incorporating all the excitement of daily imaging into the delivery of IMRT.” IGRT is going to make IMRT better and safer and more effective, he says. In fact, IGRT should have come before IMRT. “IMRT is planning conformal treatments. IGRT makes sure they are accurately delivered.” That accuracy can help decrease the diarrhea, rectal bleeding, and urgency that are common side effects of radiation therapy on prostate tumors.
Other radiation oncologists are using ultrasound to check up on those subtle movements. With ultrasound, the planning system transmits the data to a special computer that controls ultrasound. The ultrasound probe takes pictures of the prostate, bladder, and rectum. The equipment then moves the table to match the organs’ current location with the treatment plan. That ability to be so precise for each individual course of treatment also helps cut down on negative side effects but increase cure rates. “Treating the prostate, I know that I can draw a tighter margin around it so I don’t have to treat as much uninvolved tissue,” says Albrecht. “There is less ultimate toxicity.”
It’s clear that IMRT is not just ready for prime time, but is acknowledged as a true hit show. “This is the future of radiation oncology,” says Applegate. Clinicians need to “get on board if they want to be competitive. They need to make the decision to put the capital out there and get themselves in the game.”