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December 20, 2004

Finding Partial-Breast Irradiation’s Role
By Jim Knaub
Radiology Today
Vol. 5 No. 26 P. 18

Just how “experimental” is partial-breast irradiation for treating breast cancer?

The answer depends on whom you ask and how you ask the question. At what stage is the tumor discovered and treated? Are you talking about interstitial brachytherapy or using a balloon catheter? Or maybe an extra boost of 3-D conformal radiation to the patient’s lumpectomy site after surgery? Even when you’re comparing apples to apples, you might be comparing Red Delicious to Granny Smith.

Interstitial brachytherapy techniques have been around for roughly 12 years. The balloon catheter brachytherapy technique received FDA approval in 2002. Both deliver radiation only to the tissue where cancer is most likely to recur, minimizing radiation exposure to healthy tissue. But being declared “safe and effective” by the government doesn’t make them automatic alternatives to the breast conservation therapy standard of lumpectomy and whole-breast external beam radiation.

Larger Studies Underway
This kind of medical debate usually doesn’t end until the results are in from at least one large, well-controlled, randomized clinical trial. In this case, that particular study is just getting started. The National Surgical Adjuvant Breast and Bowel Project (NSABP) plans to launch a large study on partial-breast irradiation in February 2005, said Martin Keisch, MD, who has used partial-breast irradiation for 10 years and is a proponent of the procedure. Keisch said the study will evaluate three types of partial-breast irradiation—interstitial brachytherapy, balloon catheter brachytherapy, and 3-D conformal irradiation to the postsurgical lumpectomy site—against whole-breast radiation after lumpectomy. According to Keisch, half of the 3,000 patients in the study will receive lumpectomies and whole-breast irradiation. The other 1,500 patients will receive one of the three partial-breast treatments as determined by the physician and patient on an individual basis.

“[The NSABP study] will be another excellent data set in eight years,” Keisch said.

Evolving Technique
In the meantime, Keisch remains an advocate of partial-breast irradiation, particularly using the MammoSite balloon catheter approach. Developed by Proxima Therapeutics, Inc., MammoSite is a less complex way to perform brachytherapy. After lumpectomy, a physician inserts a balloon catheter into the breast and inflates it with saline to conform to the shape of the lumpectomy site. The catheter can be inserted at the time of surgery or up to 10 weeks after the operation. For the treatment, the radiation oncologist inserts a thin wire with a radioactive seed into the cavity to deliver radiation to the area immediately surrounding the tumor site—the area where tumors are most likely to recur. The radiation treatments are performed twice per day, usually for five days. After the treatments are completed, a physician deflates the balloon and removes the catheter.

Interstitial brachytherapy delivers radiation through a series of catheters—as many as 30—around the tumor site. Radioactive seeds are delivered into each catheter to treat the target area. Like the balloon catheter approach, the treatments are done twice per day, typically for five days. When the treatment series is complete, the catheters are removed from the breast.

Partial-breast external beam radiation is the third option. After lumpectomy, the patient can receive radiation therapy targeted just to the tumor site.

Keisch believes the NSABP research will confirm earlier, smaller studies showing partial breast irradiation results comparable to the standard breast-conservation therapy. He has performed approximately 250 balloon catheter brachytherapy procedures in his practice with no local tumor recurrences.

“Overall, our results may be equal, a little better, or maybe a little worse,” Keisch said, “but they are acceptable.

“It will be the phase 3 trial that convinces everyone,” he adds. “It will be the process of the phase 3 trial that convinces many.”

Most people in the radiation oncology field agree that partial-breast irradiation is a promising technique, but still demand large, multicenter studies that confirm encouraging earlier results before anointing the procedure a standard alternative. Gary Freedman, MD, is a radiation oncologist at Fox Chase Cancer Center in Philadelphia. In an article published by HealthDayNews last year, Freedman succinctly summed up the argument for the cautious approach: “Five-year results aren’t long enough to say, ‘This is a standard alternative.’”

In the same article, Freedman supported further controlled clinical research of the technique. Like many in radiation oncology, he simply doesn’t want to replace a time-proven treatment standard without supportive data from a large, controlled trial—results the NSABP could someday provide.

Varying Results
One issue in partial-breast irradiation using brachytherapy is the variability of results among different physicians. Interstitial brachytherapy requires using image analysis to place numerous catheters around the tumor site. It’s a complex, highly skill-dependent procedure. Keisch, who teaches courses on brachytherapy techniques, said he’s offered to train hundreds of radiation oncologists but only one has adopted the approach.

The balloon catheter approach simplifies the procedure by using a single catheter inserted into the tumor cavity and inflating the balloon to expose the surgical treatment margin. It’s easier to perform, making it more appealing to physicians. Since MammoSite’s approval in 2002, roughly 6,000 patients have had the balloon catheter treatment, Keisch said. That’s a large increase from his estimate of 1,000 women who underwent interstitial brachytherapy for breast cancer between 1992 and 2002.

“MammoSite is a much easier, more quality-assured technique,” Keisch said. “It appeals to surgeons because it makes sense.”

“MammoSite has had a profound impact on the field of partial-breast irradiation by simplifying the internal delivery of radiation and allowing patients to complete their treatment faster than with traditional whole-breast radiation,” said Alan Stolier, MD, a surgeon at Louisiana State University and coauthor of a study on 43 patients who underwent balloon catheter brachytherapy after lumpectomy. Results of that study were presented at the annual meeting of the American Society for Therapeutic Radiology and Oncology in Atlanta this past October. With a mean follow-up time of 29 months (range: one to 41 months), none of the patients have had a local recurrence. Among patients with at least two years’ follow-up, 91% reported good to excellent cosmetic results.

“We are encouraged that this three-year study shows women who have been treated with MammoSite have had positive results and we look forward to providing the medical community with additional long-term data as time progresses,” Stolier added.

Shorter Treatment
Based on his experience and the presumption of equivalent results and outcomes in properly selected cases, Keisch believes the patient benefits from the shorter radiation therapy treatment. Brachytherapy treatment typically takes five days while radiation therapy often runs six or seven weeks.

In a separate large study recently begun, the American Society of Breast Surgeons completed enrollment of 1,589 patients into the MammoSite Patient Registry.

“The American Society of Breast Surgeons intends to utilize data from the MammoSite Patient Registry to continually update the guidelines on the use of partial-breast irradiation,” said Peter Beitsch, MD, director of the Dallas Breast Center and coprincipal investigator of that study. “We feel it is a tremendous accomplishment to have completed enrollment and now focus on our analysis of this important treatment option, which allows women to complete radiation therapy in just five days. Information obtained from the registry will help our colleagues determine which patients will benefit most from MammoSite, ultimately increasing access to breast-conserving therapies for patients.”

Part of answering the question about partial-breast irradiation is clarifying the question being asked. The MammoSite Patient Registry will compile the largest data set of patients receiving the same balloon catheter technique.

“As a minimally invasive and shorter treatment option, MammoSite has been widely accepted by both doctors and patients,” Keisch said. “It is important to follow MammoSite patients closely to continue to gather information on their long-term outcomes and to ensure responsible application of this technology.”

Patient Selection
Keisch believes patient selection is one of the key criteria in finding the ultimate role for the technique. In his practice, Keisch presents the balloon catheter approach as an option only to patients who are diagnosed with early-stage invasive ductal cancer presenting with small tumors and two or fewer lymph nodes involved. While the indication is narrow and specific, Keisch noted that roughly one-half of early-stage breast cancer diagnoses meet that criteria.

Interestingly, he thinks that the same careful selection criteria that has produced good clinical results has been held against him and other proponents of the procedure. “We sometimes hear, ‘Your results are so good because you’re picking the best patients,’” Keisch said. “To that, we say, ‘Yes, thank you. That is our goal.’”

These days, patients are increasingly aware of treatment options and alternatives and can use that knowledge (albeit often incomplete) to pressure physicians. Brachytherapy is no exception. The appeal of a shorter course of radiation therapy—days instead of weeks—has tremendous appeal to many patients. It’s obviously important that physicians resist the pressure to use the technique in cases where it’s not appropriate just because it offers a shorter treatment course. Patient pressure to use the approach when it might not be indicated is a concern of many radiation oncologists.

Still, Keisch gives the balloon catheter approach his strong personal endorsement and caveat of good results “in my hands.” He plans to continue using the technique in his practice while waiting for the broader results of the new and ongoing studies. He believes they will show its effectiveness when performed by many physicians. He likens radiation oncologists’ acceptance of balloon catheter brachytherapy to the shift to breast conservation therapy. “It reminds me of when breast conservation was just starting.” Keisch says. “Nobody would do lumpectomies with candidates for breast conservation.”

He also understands the caution and semi-patiently proceeds with his practice while study data accrue. “We’ve had this groundswell of interest based on surgeons, patients, and some radiation oncologists,” Keisch said. “People are very to slow to change. They are doing due diligence.”

The answer to the partial-breast irradiation question still very much depends on whom you ask and how you ask the question. With good results in many individual cases and larger trials on deck, a consensus seems to be moving closer.

— Jim Knaub is editor of Radiology Today.

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