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Objective:Treatment of breast cancer patients with adjuvant brachytherapy using the MammoSite catheter is becoming a common practice due to its short duration of therapy and association with low rates of local recurrence in selected patients. We compared the long-term local toxicities of this therapy with whole breast radiation therapy.
Design: Retrospective study.
Setting: Academic medical center.
Patients: All patients who underwent breast conserving surgery and were treated with MammoSite brachytherapy at our institution between 2003-2008. We defined a control group as all patients treated during the same time period who met our criteria for MammoSite (unifocal invasive ductal cancer, tumor diameter < 3 cm, node negative, patient age >45) but chose whole breast radiation therapy.
Main Outcome Measures: Rates of fibrotic masses requiring biopsy, telangectasias and local recurrence.
Results: The 71 MammoSite patients and 245 control group patients were well matched with regard to age, mean tumor diameter, ER positivity, and treatment with systemic therapy. Median follow-up was 4 years. Telangectasias more frequently developed in the MammoSite group than in the controls (24 vs 4%, p < 0.001). A fibrotic mass which was concerning enough for local recurrence to warrant core biopsy developed at the site of the lumpectomy in 21% of the MammoSite patients and only 8% of controls (p = 0.004). There was no difference in the in-breast recurrence rate (4.2% MammoSite vs 2.9% controls).
Conclusions: Fibrotic masses requiring biopsy and telangectasias are common events after MammoSite brachytherapy, and occur more frequently after MammoSite than whole breast radiation therapy. This increased rate of long-term local toxicity should be considered when deciding on the form of adjuvant radiation therapy after breast conserving surgery.