Radiotherapy packs punch, spares surrounding tissue
Studies find benefits in new approach
Radiotherapy is a major tool in the clinician's arsenal against cancer, and new techniques are being developed that minimize damage to healthy tissue next to the targeted cancerous tumors, as well as improve the treatment effect by concentrating the radiation dose where it is most needed.
One of the most promising of these techniques is intensity-modulated radiation therapy or IMRT, an advanced form of radiotherapy that is producing positive results in many different types of tumors including prostate cancer, breast cancer, head and neck cancers, brain cancer, and pediatric malignancies. Further, studies show that some of the more sophisticated forms of IMRT are showing particular promise in treating complex tumors that are gradually shrinking, as well as tumors that are difficult to target because they are in parts of the anatomy that are constantly moving due to patients' respiratory function.
That issue is a significant one with respect to lung cancer, according to Madhur Garg, MD, a radiation oncologist who specializes in IMRT at Montefiore Medical Center in New York City. "It is very difficult to target these tumors," Gard says. However, by using four-dimensional planning, which uses a CT scan movie to pinpoint cycles of breathing, and respiration gated treatment delivery, which matches the radiation to the breathing cycles, the treatment is more precise and powerful, according to Garg.
"When the tumor is at the point of least movement, we identify that phase of the respiratory cycle and deliver the radiation during that time," he says.
In fact, in an unpublished study of the approach in patients with lung cancer, Garg and colleagues found that by employing IMRT, the average dose of radiation used was reduced by 20% to the esophagus and by 30% to the area of the lung that is most critical to breathing. "You can deliver a higher therapeutic dose to the tumor using IMRT in a much better and safer way" than with 3-D conformal radiation therapy (CRT), says Garg.
A standard practice
The use of IMRT has become standard practice at Montefiore, according to Garg. He estimates that the organization performs 1,200 to 1,500 new cases every year.
The approach also has become standard practice in the treatment of breast cancer at Fox Chase Cancer Center in Philadelphia, PA, where studies have shown that women treated with IMRT are less likely to develop serious dermatitis from the treatment than from CRT.
Gary Freedman, MD, director of radiation oncology residency and fellowship at Fox Chase, suggests that IMRT may offer the most benefit over CRT to women with large breasts because it facilitates dose homogeneity, and skin dermatitis is a more significant problem in these women.
However, Freedman stresses that it is also particularly helpful in women with breast tumors on the left side where the precision of IMRT is helpful in sparing the heart from radiation exposure. "We also like to use IMRT for patients with breast reconstruction to minimize complications that are common with CRT, and we like to use IMRT when we are giving a concomitant breast boost to shorten treatment time," he says.
"Even a small-breasted woman with a right-sided breast cancer could have a better looking treatment plan with IMRT. It is just that the comparative difference with what was achievable with [CRT] is smaller, so that [some payers] begin to weigh if the added complexity and cost is needed."
There is no question that IMRT requires more time and resources to perform. Freedman points out that the procedure requires several additional hours of planning and support from both the physics department and the physician. "Most departments in a community setting that rely on one physicist could be swamped trying to do a lot of IMRT cases," he says.
While the resources required to offer IMRT are greater than for CRT, at least some of those costs potentially could be offset with shortened treatment times. Freedman acknowledges there is wide variation from state to state in reimbursement policy for IMRT.
Radiotherapy is a major tool in the clinician's arsenal against cancer, and new techniques are being developed that minimize damage to healthy tissue next to the targeted cancerous tumors, as well as improve the treatment effect by concentrating the radiation dose where it is most needed.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content