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The University of Virginia Cancer Center has developed a new method for delivering radiation therapy along with less invasive surgery in a more precise and personalized manner.
Shayna L. Showalter, MD
Assistant Professor, Surgery
Division of Surgical Oncology
University of Virginia Cancer Center
Although treatment for early-stage breast cancer offers excellent survival outcomes and low rates of disease recurrence, there is a need for improved radiation therapy strategies that would encourage more patients to pursue optimal, evidence-based choices. The University of Virginia (UVA) Cancer Center has developed a new method for delivering radiation therapy along with less invasive surgery in a more precise and personalized manner. Because more than half of the women diagnosed with breast cancer annually in the United States have early-stage disease, the potential impact of the UVA Cancer Center research is widespread.
Surgical treatment options for early-stage breast cancer include mastectomy or breast-conserving therapy (BCT), which involves a lumpectomy followed by radiation therapy, typically in the form of whole-breast irradiation (WBI). Large randomized clinical trials have established that mastectomy and BCT with WBI are appropriate treatment options for early- stage breast cancer, with equivalent survival outcomes.1-7 In 1990, the National Institutes of Health issued a consensus statement that supported the use of BCT and WBI as the preferred management for patients with invasive breast cancer.8 This report was followed by widespread adoption of BCT with WBI. BCT without WBI is associated with an unacceptably higher recurrence rate and a potential increase in mortality.1,9-11
However, despite the potential advantages of BCT, many eligible women opt instead to undergo mastectomy because of the long- and short-term adverse events (AEs) associated with WBI and the burden of treatment, which involves traveling to a radiation facility for daily treatments for 3 to 6 weeks.12 In addition, 20% of women who are treated with BCT never receive radiation as part of their treatment.13 Multiple factors contribute to the lower than expected use of BCT and the associated underutilization of adjuvant radiation, including cost, specific tumor characteristics, patient social and demographic factors, physician/patient bias, distance from the radiation facility, and lack of social support.12-15
Besides being time consuming and inconvenient for patients, WBI has other potential downsides, such as deleterious effects on adjacent tissues including the heart, lungs, ribs, contralateral breast, adjacent normal breast, and skin.16-18 Recent data on the use of WBI have demonstrated that it is associated with a dose-dependent increase in long-term incidence of ischemic heart disease.19 Theoretically, a safer and more convenient approach to adjuvant radiation therapy could allow more patients to choose BCT, decrease the number of patients treated with BCT who never receive adjuvant radiation, and reduce the complications associated with radiation therapy after BCT.We know that a majority of breast tumor recurrences, after treatment with BCT and WBI, occur in the same area of the breast as the original cancer.20-22 Accelerated partial-breast irradiation (APBI) is a modern alternative to WBI that makes BCT a realistic and palatable option for more women because it involves treating a limited and targeted volume of breast tissue in a much shorter course than traditional WBI and with less radiation to the heart. APBI has been studied in several large clinical trials with more than 10 years of follow-up and it is believed to be safe and effective in the local control of early-stage breast cancer.23-25Intraoperative radiation therapy (IORT) is a form of APBI that involves the delivery of a single fraction of radiation at the time of BCT. Primarily due to patient demand, IORT is becoming increasingly popular in the community because it offers maximal patient convenience and results in fewer skin and cardiac AEs when compared with WBI. Limitations to conventional breast IORT (CB-IORT) include lack of imaging for treatment planning and poor dosimetry.26 CB-IORT is performed in a standard operating room without a computed tomography (CT) scanner. The delivered doses result in a nonadjustable sphere or ellipsoid, with high doses to the applicator surface (20 Gy) and low doses to at-risk tissue 1 cm from the applicator (5-7 Gy).
Results from the TARGIT-A trial revealed 5-year breast cancer recurrence rates of 3.3% after CB-IORT, compared with 1.3% after WBI. The observed difference in recurrence rates satisfied the TARGIT-A trial’s prespecified statistical definition of equivalence for CB-IORT and WBI,27,28 but elicited apprehension among physicians. Despite strong patient interest and rapid adoption of CB-IORT in the United States,29 concerns regarding the efficacy of IORT have limited utilization and stimulated acrimonious debate among experts.30-32UVA Cancer Center has a unique, integrated brachytherapy suite with in-room CT imaging, shielding for high-dose rate (HDR) delivery, and an operating room table with full anesthesia capability (Image 1). The multidisciplinary breast team at the center developed Precision Breast IORT (PB-IORT), a novel form of IORT that leverages CT imaging to confirm applicator positioning, 3-D treatment planning, and an HDR brachytherapy iridium-192 source, to safely and accurately deliver a radiation therapy dose that is roughly twice the dose of CB-IORT methods. A phase I trial was conducted that established the safety and feasibility of PB-IORT.33 A multicenter phase II trial designed to establish the long-term efficacy of PB-IORT is accruing patients at UVA Cancer Center and at Thomas Jefferson University in Philadelphia, Pennsylvania.
The surgeon then returns to the brachytherapy suite, removes the catheter, and closes the incision in the breast. The patient is awakened and is able to return home the same day. In this fashion, patients with early-stage breast cancer are able to have their cancer removed and their customized HDR brachytherapy delivered all in one day.
In summary, the potential benefits of PB-IORT include (Image 2):
When a patient is treated with PB-IORT at UVA Cancer Center, the BCT is performed in the brachytherapy suite. The surgeon then places a multilumen brachytherapy catheter into the lumpectomy bed. Next, without moving the patient, a CT image is obtained. This image facilitates confirmation of balloon placement and allows for any necessary adjustments to maximize the conformity of the breast tissue and the balloon. The physicist and radiation oncologist use the CT images to customize the radiation treatment plan. The 3-D treatment planning and multilumen catheter facilitate sculpting the dose away from normal tissues and allow for concentration of the dose in the specific area of the breast from which the tumor was removed. After the plan is made, the catheter is connected to the HDR brachytherapy source and the radiation treatment is delivered.