3D Ultrasound Used with Breast Cancer Treatment Planning Better Defines Treatment Region

Researchers report that the use of three-dimensional (3D) ultrasound provided enhanced image information to enable radiation oncologists to better define the treatment region when delivering partial breast irradiation treatment (PBI) for breast cancer.

The Clarity breast system marks the first application of 3D ultrasound technology to image-guided radiation therapy (IGRT). The system was developed by Resonant Medical Montreal, Canada), an innovator of 3D ultrasound image-guided adaptive radiotherapy products. The study was published in the February 1, 2009, issue of the International Journal of Radiation Oncology Biology Physics.

The study, conducted at the Radiation Therapy Program, British Columbia Cancer Agency, Vancouver Island Center (Canada) and the University of British Columbia (Vancouver, Canada), examined 20 consecutive cases of early-stage breast cancer where the patients were treated with breast-conserving surgery. Researchers found that in 40% of cases, the variability between lumpectomy cavity contours was reduced when ultrasound was used instead of computed tomography (CT) imaging--the current standard of care for planning breast cancer treatment. Specifically, 3D ultrasound proved to be particularly beneficial for imaging patients with dense breasts and small cavities.

"Precision in planning and the increased certainty that radiation is being delivered to the exact area where it is needed have never been more critical, with the percentage of patients opting for breast conservation therapy and PBI on the rise," said Pauline Truong, M.D., C.M., a researcher on the study. "Following this study, however, it is clear that the benefits of this technology could be applicable to not only PBI patients, but those undergoing whole breast radiation and electron boost therapy--potentially helping an even larger population of women with breast cancer."

The Clarity system was approved by the U.S. Food and Drug Administration (FDA) in 2004 for guidance in the treatment of prostate and breast cancers. In addition to its application with treatment planning, the Clarity system is also used to image the lumpectomy cavity daily with each radiation treatment, to get an actual visual image and location of the tumor cavity on a regular basis. While the breast cancer radiation oncology community is aware that the location of the lumpectomy cavity target can change throughout the course of treatment, this issue is still largely unaccounted for in current treatment protocols.

Clinical consequences can include delivery of radiation to healthy tissue, application of radiation too close to the chest wall or skin, and in some instances, under-treatment of certain areas. Clarity provides the first method of daily lumpectomy cavity monitoring that is based on visualization of the actual anatomy--rather than an estimation of the location of the cavity. This precision in planning and treatment could enable physicians to reduce the field of radiation they need to deliver, which is always preferable if clinically justified.

Several studies detailing the benefits of the use of Clarity during breast cancer treatment have also been presented in recent months. For example, data from a study conducted at McGill University (Montreal, Canada) and the University of Vermont (Burlington, VT, USA) was presented investigating the use of the Clarity system to track tumor cavity movement prior to daily treatments. The study compared the use of 3D ultrasound to CT, and found that these techniques were statistically equivalent. Researchers concluded that because ultrasound is non-ionizing and noninvasive, it is preferable to daily CT for tumor cavity monitoring.

Moreover, at the 2008 meeting of the Radiological Society of North America (RSNA) in Chicago, IL, USA, data collected at Beth Israel Medical Center (New York, NY, USA) on the use of Clarity when delivering electron boost therapy was examined. Although electron boost treatments have been delivered for quite a while, there has been no way to ensure that the electron dose is treating the correct area. This study found that in 45% of treatments, part of the tumor cavity would have been outside of the dose region and would have been missed without ultrasound guidance.

"The Clarity system has been used in the treatment of thousands of prostate cancer patients, and we are encouraged by the results and feedback we have seen and heard from radiation oncologists regarding its application with breast cancer," said Tony Falco, Ph.D., FCCP, founder and chief executive officer of Resonant Medical. "This mounting clinical evidence acknowledges the value of the Clarity system for the effective planning and treatment of breast cancer."

Resonant Medical develops, manufactures, and markets 3D ultrasound image-guided adaptive radiotherapy products. Originally developed at McGill University Health Center, Resonant's technologies are available in more than 50 cancer centers in the United States Canada and Europe.

Related Links:
Resonant Medical
British Columbia Cancer Agency
University of British Columbia