MammoSite, a type ofbreast brachytherapy (bray-kee-therapy), uses a single catheterinserted into the breast following lumpectomy, or surgical removal of atumor, to deliver a high dose of radiation. Once the catheter isinserted, a tiny balloon is inflated and loaded with radioactive seedsthat deliver prescribed levels of radiation to targeted tissuesurrounding the tumor site.
"MammoSite is a type of partialbreast irradiation that delivers radiation from the inside of thebreast directly to the tumor site where cancer cells are most likely toreside," said Sushil Beriwal, M.D., assistant professor at theUniversity of Pittsburgh School of Medicine and medical director ofradiation oncology at Magee-Womens Hospital of the University ofPittsburgh Medical Center (UPMC). "Ours is one of the largestsingle-institution studies to confirm that it does this safely and withan acceptable level of toxicity."
The study, which was designedto evaluate early outcomes of MammoSite brachytherapy, and was approvedby the FDA in 2002, evaluated toxicity in 100 patients treated betweenJune 2002 and October 2004 at the University of Pittsburgh CancerInstitute. The patients were followed between three and 30 monthssubsequent to treatment with an average follow-up time of one year.After treatment, patients were assessed at one week, one month and atthree-month intervals. While 14 percent of women had to have thecatheter removed because of various reasons, the majority of thepatients (86 percent) underwent treatment.
Post-treatmentcomplications included balloon rupture, infections, skin toxicity andseromas (persistence of the cavity where the lump was removed). Studyresults indicated that balloon rupture occurred in six patients (7percent) and wound infections occurred in 10 patients (12 percent). Nopatients had serious skin toxicities from treatment. A palpable seromawas observed in 34 of the patients (40 percent) and persisted beyondsix months of treatment in 22 patients (26 percent).
The studyalso evaluated cosmetic outcome of MammoSite treatment. Cosmeticoutcome refers to the physical similarity between the treated breastand the untreated breast. Forty-eight patients (56 percent) hadexcellent cosmetic outcomes; 32 patients (37 percent) had good cosmeticoutcomes; and seven patients (7 percent) had fair cosmetic outcomes.
"Ourfindings demonstrate that the toxicities associated with MammoSite weresimilar to results reported in the MammoSite brachytherapy registrytrial," said Dr. Beriwal. "The complications were acceptable and thecosmetic outcome was comparable to what we might see with standardexternal beam radiation." Dr. Beriwal added that follow-up studies willseek to assess the long-term effects as well as the efficacy of thetreatment compared with standard external beam radiation therapy andother types of breast brachytherapy.
MammoSite is manufactured by Cytyc Corporation based in Alpharetta, Ga.
Alsoinvolved in the study from the University of Pittsburgh's department ofradiation oncology were Anurag Agarwal, M.D.; Dwight E. Heron, M.D.;Jeffrey Falk, M.D., Ronald Johnson, M.D.; Robert Mogus, R.T.T.; HayeonKim, M.S.; Kristina Gerszten, M.D.; and Melvin Deutsch, M.D.
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