Seroma is an expected consequence and not a complication of MammoSite brachytherapy

Seroma has long been listed as a complication of MammoSite brachytherapy. Palpable abnormalities are clinically apparent months after treatment and a vast majority of patients demonstrate seroma formation in radiologic studies. We embarked on this study to evaluate the actual sonographic incidence and eventual sonographic resolution, possible contributing factors, cosmesis, pain, and local control associated with seroma formation after MammoSite partial breast irradiation (PBI). We investigated 160 patients who underwent MammoSite PBI from 2002 to 2006 of whom 100 patients had serial sonographic information. Clinical and tumor variables, infection, pain, and cosmesis were investigated. Dosimetric data including volume of balloon, dose at balloon surface, and at skin were analyzed. After a median follow-up of 36 months, the incidence of sonographically confirmed post-radiation seroma was 78% within the first 1 year following radiation and steadily decreased with time. The average size of a seroma cavity was 2.3 cm (range 0.6-6 cm) with a decline to an average of 1.4 cm after 1 year, with complete resolution in 65% of patients at 2 years. No statistically significant correlation was found between patient characteristics, tumor variables, and volumetric or dosimetric data for seroma formation. Excellent/good cosmetic scores were achieved in 94% of women with and 92% without seroma. Local control was equivalent between patients with and without seroma. Consecutive sonographic imaging reveals a high rate of seroma formation after MammoSite PBI, with resolution in 65% of patients by 2 years without intervention. Seroma formation does not prevent an excellent cosmetic result or alter local control.