According to new research from The University of Texas MD Anderson Proton Therapy Center at Houston, early stage breast cancer patients may benefit from accelerated partial breast irradiation (APBI) using proton therapy as opposed to conventional whole breast irradiation (WBI) in terms of duration and cost of treatment. APBI is a localized form of radiation treatment (brachytherapy) that involves the insertion of a radioactive “seed” to kill breast cancer cells that may remain after lumpectomy surgery. APBI delivers a highly effective dose of radiation while greatly reducing treatment time. This procedure requires close collaboration between the surgeon who removes the breast tumor, and the radiation oncologist who treats the tumor area after surgery.
Accelerated partial breast irradiation is performed about one to four weeks after a lumpectomy. A specialized catheter is inserted into the cavity left behind after removal of the tumor. The device remains in place during the course of APBI treatment, usually about 8-10 days.
Proton therapy is an advanced type of radiation treatment that uses a beam of protons to deliver radiation directly to the tumor, destroying cancer cells while sparing healthy tissues and minimizing side effects. Protons enter the body with a low radiation dose, stop at the tumor, match its shape and volume or depth, and deposit the bulk of their cancer-fighting energy right at the tumor.
MD Anderson says that while standard radiation therapy has evolved and improved over the years and is effective in controlling many cancers, because its X-ray beams are composed of primary photons and secondary electrons, they deposit their energy along the path of the beam, to the targeted tumor and beyond, delivering radiation to healthy tissues before and beyond the tumor site. The radiation’s euphemistically termed “exit dose” may cause negative health consequences later on due to the damage it causes in normal tissue or organs near the tumor site.
Proton treatment’s big advantage is that the physician can control where the proton beam releases the bulk of its cancer-fighting energy. Cancer specialists at the use proton therapy to precisely target and match treatment to the shape of a tumor with incredible accuracy. As the protons move through the body, they slow down and interact with electrons, and release energy. The point where the highest energy release occurs is the “Bragg peak.” A physician can designate the Bragg peak’s location, causing the most damage to the targeted tumor cells. A proton beam conforms to the shape and depth of a tumor, while sparing healthy tissues and organs.
Proton radiation, once inside the patient’s body, also has a very short life. After patients complete their treatment, they can leave the treatment room without any risks or radiation exposure to others.
The MD Anderson Proton Therapy Center — part of MD Anderson Cancer Center, which has been ranked as one of the nation’s top two cancer centers by U.S. News & World Report every year since 1990 — pioneered the innovative, extremely precise form of proton therapy known as pencil beam scanning, and continues to expand research on ways proton therapy can benefit patients. The team pioneered pencil beam proton therapy, also called scanning beam, and intensity modulated proton therapy (IMPT), The MD Anderson Proton Therapy Center is one of the few centers worldwide offering these types of proton therapy to patients.
Pencil beam technology and IMPT build on the benefits of proton therapy. With a proton beam just millimeters wide, these advanced forms of proton therapy combine precision and effectiveness, offering unmatched ability to treat a patient’s tumor and minimizing effect on a patient’s quality of life — during and after treatment. They rely on complex treatment planning systems and an intricate number of magnets to aim a narrow proton beam and essentially “paint” a radiation dose layer by layer.
There are currently three types of single-entry breast brachytherapy devices. Which to use for a given patient is determined by the surgeon and radiation oncologist based on the size and shape of the lumpectomy cavity. Each brachytherapy device is designed to hold the radioactive “seed” in designated positions within the device for defined lengths of time to insure radiation of the targeted breast tissue immediately surrounding the lumpectomy cavity:
Strut Assisted Volume Implant (SAVITM): this device has 7-11 “struts” or catheters through which the iridium seed travels (see photo above). The struts are expanded after the device is inserted into the lumpectomy cavity.
Mammosite: a balloon is inserted into the lumpectomy cavity and inflated. The original Mammosite balloon had a single lumen (catheter). The Mammosite ML has four lumens through which the iridium seed travels.
Contura MLB: This is also a balloon device with five lumens (catheters) within the balloon through which the iridium seed travels. Contura also has vacuum ports on either end of the balloon, to remove air or fluid between the balloon and the targeted breast tissue.
During treatment, the iridium seed, about the size of a grain of rice, is inserted into the catheters (lumens). The seed is within the device in various dwell positions for a total of 5-10 minutes. The seed is withdrawn and then re-inserted six hours later, for a total of two treatments a day.
MD Anderson reports that in a cost analysis study based on typical patient characteristics, researchers used Medicare reimbursement codes to analyze allowable charges for eight different types of partial and whole breast irradiation therapies and treatment schedules available to early stage breast cancer patients. Taken together, these represent roughly 98% of the treatment options available to these patients. The cost of proton therapy when used for APBI, introduced to decrease overall treatment time and toxicity, was estimated at $13,833. Comparatively, WBI using IMRT (x-ray) therapy resulted in the highest Medicare charges at $19,599. The average charges across the eight treatment regimens were $12,784; thus, proton costs were similar to that of other types of radiation.
The findings were presented at the inaugural North America meeting of the Particle Therapy Co-Operative Group (PTCOG) held at MD Anderson Proton Therapy Center. A manuscript detailing the study findings is underway.
“It is often suggested that trials of proton APBI are irrelevant due to the modality’s presumed high cost, but our data shows that this perception is false. Correcting this perpetual assumption is an important step in helping patients obtain the necessary health coverage to participate in clinical research,” says Valentina Ovalle, M.D., postdoctoral research fellow and principal investigator in a MD Anderson release. “Further, we anticipate that because charges vary proportionately across payers, the estimated Medicare reimbursement costs likely reflect relative charges to other third-party payers.”
The American Cancer Society estimates that 232,670 patients will be diagnosed with invasive breast cancer this year. Early breast cancer (stage I or II) is the most common invasive breast cancer in the U.S. With treatment, these patients generally have a good prognosis. Standard treatment approaches typically include breast-conserving surgery (BCS) followed by radiation therapy for the entire breast — five days per week, for up to six weeks, including one week of “boost” radiation to the area where the initial tumor was removed.
The role of APBI for early stage breast cancer is still being evaluated, but its intent is to deliver a highly effective dose of radiation while greatly reducing treatment time – 10 treatments twice per day over one week. Further, on average it spares at least two-thirds of breast tissue from a full dose of radiation.
“The biggest drawback to WBI is that it is inconvenient, interrupting lives,” observes Eric A. Strom, M.D, F.A.C.R., study co-author and professor in Radiation Oncology. Dr. Strom is the principal investigator of a clinical trial sponsored by the National Cancer Institute on proton APBI.
APBI is delivered via two approaches — brachytherapy and external beam. Proton therapy is offered as a type of external beam APBI and, according to Dr. Strom, is unique in its ability to provide the full dose of radiation precisely to the tumor site and nowhere else, eliminating radiation to the remaining breast, lung and heart. To date, research on proton APBI has shown effective tumor control, limited side effects and good cosmetic outcomes.
“This cost analysis must be interpreted in light of clinical evidence for proton APBI, which while still in nascent stages, is promising,” says Dr. Ovalle. “The findings counter the presumption that proton APBI is so expensive that even excellent clinical results would be immaterial. If the payment barrier for proton therapy is removed so that current and future research can proceed, the outcomes may ultimately benefit patients, physicians and insurers: better treatments at lower costs.”
Other MD Anderson researchers contributing to this study include Joy Godby, B.A., Simona F. Shaitelman, M.D., Ed.M., Henry M. Kuerer, M.D., Ph.D., Wendy A. Woodward, M.D., Ph.D, and Karen E. Hoffman, M.D., M.H.Sc., M.P.H.
The University of Texas MD Anderson Proton Therapy Center
The American Cancer Society
The University of Texas MD Anderson Proton Therapy Center