Template-Based Interstitial Breast Brachytherapy Alone Is Effective

NEW ORLEANS—Template-based interstitial brachytherapy is an effective method for treating breast cancer, according to a study presented at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (abstract 147). The study is one of the first to use a template to position interstitial implants in its entire study population as part of its protocol.

"In properly selected patients, accelerated partial breast irradiation via interstitial techniques offers 5-year results comparable to contemporary standard breast conservation therapy with whole breast external beam radiation therapy," said lead investigator Peter Y. Chen, MD, associate director of education, Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan.

Brachytherapy involves placing multiple catheters or needles into and around the site of the lumpectomy. For low-dose-rate brachytherapy, a number of radioactive sources are then manually afterloaded into the catheters. In contrast, for high-dose rate brachy-therapy, one high-activity iridium-192 source is remotely afterloaded sequentially into each of the needles in a specified amount of time at designated dwell positions to deliver precise doses of radiation.

Conventional placement of the catheters or needles has been freehand guided. A template allows exact geometric placement of the catheters/needles, which improves the physician’s ability to target and control the delivery of radiation to the tumor site. The template holds the breast physically in place and, in conjunction with diagnostic imaging, provides a navigational aid in placing the catheters/needles in the tumor bed. For women receiving high-dose-rate outpatient therapy, the needles remain in place for the 4 to 5 days of twice-daily treatment.

In the study, 199 women with early-stage breast cancer were treated according to one of three protocols of tumor bed irradiation alone: low-dose-rate implant with I-125 as the radiation source treated continuously as an inpatient (50 Gy over 96 hours) (n = 122) or high-dose-rate implant with Ir-192 as the radiation source treated as an outpatient (32 Gy in eight twice-daily fractions or 34 Gy in 10 twice-daily fractions) (n = 77). Every implant was designed to irradiate the lumpectomy cavity plus a 1- to 2-cm margin.

Patients ranged in age from 40 to 90 years (median, 65). Median follow-up on all patients was 5 years (6.3 years for the low-dose-rate patients and 3.1 years for the high-dose-rate patients). A total of 129 patients (65%) have been followed for 4 or more years, 95 (48%) for 5 or more years, and 70 (35%) for 6 or more years.

The study originally included patients with up to three positive lymph nodes, but was revised in 1997 to exclude patients with any positive nodes. Other exclusion criteria included pure ductal carcinoma-in-situ, infiltrating lobular histology, an extensive intraductal component, and significant lobular carcinoma- in-situ, as well as breasts that were technically not suitable for the implant.

Study Results

Dr. Chen and his colleagues observed two true recurrences (TR)/marginal misses (MM), for a 5-year actuarial rate of 0.5%. Five-year actuarial cause-specific survival was 97%. Good to excellent cosmetic results were noted in 91% of patients receiving low-dose-rate brachy-therapy and 98% of patients receiving high-dose-rate brachytherapy.

Overall, five patients had ipsilateral breast failure (two TR/MM), and three had elsewhere breast failures, for a 5-year actuarial local recurrence rate of 1.2%. The 5-year actuarial regional failure rate was 1.1%. Time to failure (local recurrence requiring salvage mastectomy) was between 1.5 and 7.6 years. One patient with treatment failure died of the disease. This patient had simultaneous regional and distant failure at the time of local recurrence. She also had three positive lymph nodes and thus would not be treated with brachytherapy today.

Toxicity

The most common toxicity was the appearance of very fine telangiectasia, noted on close inspection at the needle entrance and exit sites, in 30% of patients receiving low-dose-rate brachyther-apy and 24% of patients receiving high-dose-rate brachytherapy. Asymptomatic fat necrosis was found in 19% of low-dose-rate and 8% of high-dose-rate brachytherapy patients; late infections were seen in 7% of low-dose-rate and 1% of high-dose-rate patients.

Importance of Patient Selection

Appropriate patient selection is extremely important to achieving success with breast brachytherapy procedures, Dr. Chen said. He recommends that patients be older than 40 years, with infiltrating ductal cancers no larger than 3 cm, negative surgical margins of at least 2 mm, and no positive axillary nodes. "Under our guidelines and technique in appropriately selected patients, the 5-year actuarial local recurrence rate is very low at 1.2%," he said. He cautioned that this form of treatment be performed in an investigational setting until longer follow-up of 10 and 15 years is available.