RSNA: Partial-Breast Radiation May Be Option After Lumpectomy

CHICAGO, Nov. 30 -- Partial breast irradiation using a percutaneous brachytherapy balloon may be a safe and efficient alternative to whole breast radiation, according a small single-center series.

Standard whole breast external beam radiation usually requires six weeks of five-days-a-week treatment, while the partial breast irradiation regimen "can deliver the full dose of radiation in five to seven days," said Ellen B. Mendelson, M.D., director of breast imaging at Northwestern Feinberg School of Medicine here.

Dr. Mendelson reported at the Radiological Society of North American meeting here on Northwestern's experience with percutaneous ultrasound-guided placement of the Mammosite catheter (Cytyc Corp., Marlborough, Mass.).

She said that partial breast radiation to the site of the lumpectomy "is an intuitive approach since the literature suggests that recurrence is most likely to occur in the region of the original lesion."

The catheter, which is typically placed one week to several weeks following breast conservation surgery, is one of several partial breast radiation techniques being tested in a 3,000-patient national trial comparing partial with whole breast radiation regimens.

Dr. Mendelson said the results of that national trial, which won't be reported for at least two more years, are likely to provide the final word on the efficacy of catheter-based partial breast radiation regimens.

Ahead of those results, Northwestern and several other centers have been moving forward with partial breast irradiation in a carefully selected subset of breast cancer patients.

Eligibility for the procedure includes tumors smaller than 2.5 cm (stages 0, 1, and 2) with negative margins and negative lymph nodes following lumpectomy, she said.

As opposed to surgical placement at the time of lumpectomy, ultrasound-guided interventional techniques allow time for pathologic analysis and patient decision. She noted that it often takes several days for a full pathology report, "which works well with an ultrasound-guided percutaneous placement of the balloon, rather than placement at the time of surgery, when pathology is not yet available."

When the tumor is removed the remaining cavity fills with fluid, the seroma. Dr. Mendelson said a key factor in selecting patients for the balloon brachytherapy procedure was the skin-to-seroma thickness, because a thickness of at least 0.6 cm was required for safe delivery of the full radiation dose.

Among 75 women assessed for partial breast radiation at Northwestern from May of 2002 through April 2006, 44 met the entry criteria. "Most of the women who failed to meet the criteria did so because the tissue thickness between seroma and skin was less than 0.6 cm," she said.

The catheter was inserted using topical anesthesia and was filled with 5 ml of non-ionic contrast agent and up to 60 ml of saline -- enough to fill the entire seroma.

The patients were then sent to radiation oncology for a second measuring of the thickness between the seroma and the skin and CT-based dosimetry to determine the dwell position of the high-dose rate Iridium-192 sources, which were delivered to the balloon through a port in the catheter.

Over the next five to seven days, 10 fractions with twice-per-day (3.4 Gray) brachytherapy were delivered.

Thirty five of the eligible women agreed to partial breast irradiation and 34 successfully completed treatment. One woman who was considered eligible at first measurement was found to be ineligible when the skin to seroma thickness discovered to be too thin at the second measurement.

There were no complications during catheter placement or removal, but one catheter ruptured during treatment and required replacement.

Dr. Mendelson said there have been no reported recurrences yet, but she said the series was too small and the follow-up too short to draw any conclusions about disease-free survival.