Intensity modulated radiation therapy reduces radiation dose to healthy breast tissue

Results from a University of Pittsburgh study evaluating intensity modulated radiation therapy (IMRT) for breast cancer indicate that IMRT results in a lower dose of radiation to healthy breast tissue when compared to standard radiation. The findings were presented today at the 46th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) in Atlanta.

“More than 70 percent of breast cancer patients receive ionizing radiation therapy to treat their disease,” said Dwight E. Heron, M.D., study co-author and assistant professor of radiation oncology, University of Pittsburgh School of Medicine and vice chairman of radiation oncology, University of Pittsburgh Medical Center. “While these high-energy beams are targeted to the tumor site as precisely as possible, they often inadvertently injure healthy breast tissue that surrounds the tumor site, limiting the doses of radiation that can be used to effectively destroy cancer cells. With this study, we sought to discover whether tightly focused radiation beams, such as those provided by IMRT, would make a difference in the amount of radiation received by the side of the breast opposite from the tumor site.”

In the study, 65 patients with breast cancer who had received breast-conserving surgery were treated with IMRT using the Eclipseâ Planning System, Varian Medical Systems, and compared with 18 patients treated with conventional 2D or 3D radiation therapy. Results indicated a 35 percent reduction in radiation dose to the breast opposite the tumor site at the 4 cm position from the patient’s midline and a 57 percent reduction at the 8 cm position in favor of those patients treated with IMRT.

“These results are encouraging evidence that breast cancer patients can benefit from IMRT,” said Dr. Heron. “With more homogenous and conformal treatment, breast cancer patients may be spared side effects from standard radiotherapy that can include skin irritation and breakdown and scarring of the lungs. The risk of treatment-related heart complications, though rare, also may be further reduced with IMRT.”

During radiation therapy, high-energy beams are aimed at cancer cells to destroy them by permanently damaging their underlying genetic material. Unlike standard radiation therapy, IMRT administers a radiation field that consists of several hundred small beams of varying intensities that pass through normal tissue without doing significant damage, but converge to give a precise dose of radiation at the tumor site. IMRT can potentially limit the adverse side effects from radiation while increasing the intensity of doses that can be given to effectively destroy cancer cells.

IMRT is combined with a process called inverse treatment planning to determine the best way to treat a patient. It relies on CT (computed tomography) data from patients that is processed and analyzed by a complex computer system to produce the ideal radiation dose distribution for that patient.

Co-authors of the study include Deborah Sonnick, C.M.D.; Ajay Bhatnagar, M.D.; Edward Brandner, Ph.D.; Kristina Gerszten, M.D.; and Melvin Deutsch, M.D.; all with the department of radiation oncology at the University of Pittsburgh School of Medicine.