Purpose: Describe the incidence and identify risk factors for seroma development after MammoSite breast brachytherapy (MBT).
Methods and materials: MBT patient data were prospectively recorded into a quality assurance database. Departmental and electronic records were reviewed to extract patient-, treatment-, and outcome-specific data. Stepwise logistic regression analysis was performed to identify factors associated with development of any seroma including the subset of clinically significant seroma (CSS). CSS was defined as a symptomatic seroma requiring multiple aspirations, biopsy, and/or excision. Variables analyzed included age, weight, number of excisions, time from resection to catheter placement, placement technique, balloon volume, dosimetric factors, and postbrachytherapy infection.
Results: MBT was performed in 109 patients, of whom 97 had minimum 6 months (median, 36) post-MBT follow-up or earlier development of seroma. All patients received 34 Gy to 1cm depth from balloon surface, delivered twice daily in 10 fractions. Seroma developed in 41% of patients at a median of 3 months (range, 0.1-25) post-MBT. One-third of seromas (13% of all patients) were CSS. The only factor identified as statistically significant for development of any seroma was catheter placement on day of resection vs. > or =1 day later (59% vs. 33%; p = 0.0066). Post-MBT infection was highly statistically significant for development of CSS (64% vs. 7%; p<0.0001). Prophylactic antibiotics reduced the risk of post-MBT infection from 37.5% to 6% (p = 0.011).
Conclusions: The incidence of CSS after MBT is low. Post-MBT infection is statistically significantly associated with CSS development, the incidence of which is reduced with prophylactic antibiotics.