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Brachytherapy to Tumor Bed After Lumpectomy a Possible Alternative to External Beam Therapy

Brachytherapy to Tumor Bed After Lumpectomy a Possible Alternative to External Beam Therapy

ROYAL OAK, Mich—Interstitial implants that deliver radiation therapy to the tumor bed alone after lumpectomy have been well tolerated with no significant acute or late toxicity in the first 50 patients in a Michigan study. In addition, with three years' median follow-up, no patients have recurred locally or distantly.

"It's still early, but we're quite encouraged with the results so far," Vinay Sharma, MD, a brachytherapy fellow at William Beaumont Hospital, said at a poster presentation of the study, which was conducted by Frank Vicini, MD, and colleagues. [See page 10 for a report on intraoperative external beam radiation in this setting.]

The pilot study, begun in March 1993, includes selected patients with early-stage breast cancer treated with breast-conserving therapy. Eligible patients had tumors less than 3 cm, margins clear by 2 mm, no extensive intraductal component, a breast technically suitable for implant, and three or fewer involved nodes.

Implants Loaded into Catheters

Patients received a 50 Gy dose to the tumor bed over a 96-hour period. The implants, radioactive iodine 125 seeds, are loaded into catheters placed within the breast. About 30% of the time, the implants are placed at the time of re-excision. "In that setting, the tumor cavity is open and we see exactly where we're putting our needles," Dr. Sharma said.

The other 70% of the time, he said, seed implantation is done as a separate operation or at the time of an axillary lymph node dissection "and then we're dealing with a closed cavity."

In these cases, the researchers use three-dimensional (3D) computed tomography and ultrasound computer reconstructions to help guide their placement of the needles.

The researchers conclude that the brachytherapy technique may provide a safe, quick, and effective alternative to standard external beam radiation therapy.

The implant method significantly decreases patient inconvenience and reduces delays in the initiation of systemic therapy, Dr. Sharma said. He noted, however, that longer follow-up will be needed to establish whether this approach is equivalent in efficacy to that of standard post-lumpectomy external beam radiation therapy.

 
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