Largest single-institution study demonstrates Mammosite is a safe breast cancer treatment

10/17/05

DENVER, Oct. 17 – Treating breast cancer with MammoSite® resulted in a low risk of complications and was generally well tolerated, according to a University of Pittsburgh School of Medicine study presented today at the 47th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) in Denver.

MammoSite, a type of breast brachytherapy (bray-kee-therapy), uses a single catheter inserted into the breast following lumpectomy, or surgical removal of a tumor, to deliver a high dose of radiation. Once the catheter is inserted, a tiny balloon is inflated and loaded with radioactive seeds that deliver prescribed levels of radiation to targeted tissue surrounding the tumor site.

"MammoSite is a type of partial breast irradiation that delivers radiation from the inside of the breast directly to the tumor site where cancer cells are most likely to reside," said Sushil Beriwal, M.D., assistant professor at the University of Pittsburgh School of Medicine and medical director of radiation oncology at Magee-Womens Hospital of the University of Pittsburgh Medical Center (UPMC). "Ours is one of the largest single-institution studies to confirm that it does this safely and with an acceptable level of toxicity."

The study, which was designed to evaluate early outcomes of MammoSite brachytherapy, and was approved by the FDA in 2002, evaluated toxicity in 100 patients treated between June 2002 and October 2004 at the University of Pittsburgh Cancer Institute. The patients were followed between three and 30 months subsequent to treatment with an average follow-up time of one year. After treatment, patients were assessed at one week, one month and at three-month intervals. While 14 percent of women had to have the catheter removed because of various reasons, the majority of the patients (86 percent) underwent treatment.

Post-treatment complications included balloon rupture, infections, skin toxicity and seromas (persistence of the cavity where the lump was removed). Study results indicated that balloon rupture occurred in six patients (7 percent) and wound infections occurred in 10 patients (12 percent). No patients had serious skin toxicities from treatment. A palpable seroma was observed in 34 of the patients (40 percent) and persisted beyond six months of treatment in 22 patients (26 percent).

The study also evaluated cosmetic outcome of MammoSite treatment. Cosmetic outcome refers to the physical similarity between the treated breast and the untreated breast. Forty-eight patients (56 percent) had excellent cosmetic outcomes; 32 patients (37 percent) had good cosmetic outcomes; and seven patients (7 percent) had fair cosmetic outcomes.

"Our findings demonstrate that the toxicities associated with MammoSite were similar to results reported in the MammoSite brachytherapy registry trial," said Dr. Beriwal. "The complications were acceptable and the cosmetic outcome was comparable to what we might see with standard external beam radiation." Dr. Beriwal added that follow-up studies will seek to assess the long-term effects as well as the efficacy of the treatment compared with standard external beam radiation therapy and other types of breast brachytherapy.

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