Brachytherapy Toxicity Acceptable in Breast Cancer Patients

NEW ORLEANS—Toxicity for low-dose-rate and high-dose-rate accelerated partial breast irradiation (APBI) (brachytherapy) is comparable to that observed in women treated with conventional whole breast external beam radiation therapy after lumpectomy, according to a 10-year study (RTOG 95-17) presented at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (abstract 146).

"Acute toxicity with wide-volume brachytherapy was acceptable considering the learning curve that each institution had to go through, and should improve with newer catheter insertion techniques, including the use of templates," concluded Robert R. Kuske, Jr., MD, professor of human oncology, University of Wisconsin, Madison, and lead investigator of the study.

Dr. Kuske is the developer of the Kuske Breast Template (Nucletron Corporation, Columbia, Maryland), which recently received FDA approval for use in guiding catheter placement in breast brachytherapy (see photograph below).

The investigators enrolled a total of 100 women between August 1997 and March 2000 to receive high-dose-rate brachytherapy (34 Gy in 10 twice-daily fractions over 5 days) (n = 66) or low-dose-rate implants (45 Gy in 3.5 to 5 days) (n = 33). Patients had invasive nonlobular breast carcinomas of 3 cm or less with negative surgical margins after lumpec-tomy and axillary dissection with 0 to 3 positive axillary nodes without extracapsular extensions. One patient was excluded for having only sentinel node mapping.

Wide-volume brachytherapy involves placing multiple catheters or needles 2 cm around the lumpectomy site to deliver precise doses of radiation "from the inside out," Dr. Kuske said. Conventional placement of the catheters has been freehand guided. The Kuske Breast Template holds the breast in place and provides a navigational aid for image-guided catheter placement. The catheters remain in place for the 4 to 5 days of twice-daily outpatient treatment.

In the current study, catheter insertion procedures were left to the discretion of each individual institution, Dr. Kuske said, and data were not collected concerning individual freehand and template techniques used to accomplish volume coverage.

Toxicity Results

With a median follow-up of 3.2 years, the grade 3-4 toxicity rate was 5% during APBI, 10% during all follow-up visits, and 4% at the last follow-up. "These rates may well be acceptable to women who would otherwise be unable to undergo conventional external beam radiation," Dr. Kuske said. In addition, he said, the scarring typical from severe skin burns that large-breasted women may experience with external beam radiation therapy is not common with brachytherapy.

Toxicities reported during brachyther-apy included erythema (n = 48), breast edema (n = 36), tenderness (n = 25), breast pain (n = 23), and infection (n = 12). The worse toxicity was a grade 4 pneumothorax after catheter insertion that required a chest tube in a patient in the low-dose-rate group.

Although chemotherapy was not part of the protocol, the investigators noted that it had a negative influence on toxicity rates. Treating physicians could choose to give chemotherapy, tamoxi-fen (Nolvadex), or both if needed, starting at least 2 weeks after brachytherapy.

Among the patients undergoing chemotherapy, 14% of patients in the high-dose-rate group and 55% of those in the low-dose-rate group had grade 3-4 toxicities. Among the patients who did not undergo subsequent chemotherapy, only 4% in the high-dose-rate group and none in the low-dose-rate group had grade 3-4 toxicities.

Dr. Kuske believes a phase III trial randomizing high-dose-rate brachyther-apy against 6 weeks of conventional radiation therapy would provide important data. "Many of the women who come to me understand that brachytherapy is not experimental, that it is just a different way to deliver a standard treatment," he said. "For women who look at the treatment options this way, choosing the 5-day option over the 6-week option is automatic."

He noted, however, that brachytherapy has only 11 years of supportive data, compared with 35 years for conventional radiation therapy. ‘There is still a large school of thought in the specialty that believes textbook teachings that every last speck of breast tissue must be treated in these favorable breast cancers," he said.

Data presented at meetings does not support this contention, Dr. Kuske said. "That 2-cm area around the lumpectomy site covers most of the volume that suffers a recurrence. So we are really intensifying radiation delivery to the site that is at greatest risk of recurrence," he concluded. In his 11 years of experience with breast brachytherapy, he said, more than 300 patients have been treated, with only three tumor recurrences in the breast.