2962 - Seroma Change during and after Breast Radiotherapy: Implications for Recurrence Assessment

Purpose/Objective(s): Seroma formation is a common sequela of breast-conserving surgery (BCS), exhibiting dynamic volume changes during and after whole-breast radiation therapy (WBRT). These fluctuations can complicate radiotherapy planning and challenge recurrence assessments. This study aims to evaluate seroma volume changes throughout WBRT and follow-up, identify associated clinical factors, and assess its impact on recurrence detection.

Materials/Methods: This retrospective study analyzed 25 patients who underwent WBRT after BCS, all presenting with visible, undrained seromas throughout radiotherapy. Computed tomography (CT) simulations were performed before WBRT and prior to tumor bed boost planning. Patients received either standard fractionation (50 Gy in 25 fractions) or hypofractionation (40.5 Gy in 15 fractions), followed by a tumor bed boost (10–16 Gy in 5–8 fractions). Seroma volumes were contoured and compared across CT scans. Follow-up included clinical assessments, physical examinations, and breast ultrasound (3–6 months), with CT scans as clinically indicated. Statistical analyses were performed using the Wilcoxon signed-rank test, Mann-Whitney U test, and Spearman’s rank correlation coefficient to examine associations between seroma volume and clinical factors.

Results: Median seroma volume decreased significantly from 23.5 cm³ (range: 3.6–214.1 cm³) before WBRT to 8.8 cm³ (range: 1.6–74.9 cm³) at tumor bed boost planning (p < 0.001), with a median reduction of 63.8%. However, 2 patients exhibited seroma enlargement during treatment. Initial seroma volume correlated with age, tumor size, and excised breast tissue volume but was not significantly associated with surgery-to-CT interval, prior chemotherapy, or diabetes status. A positive linear correlation was observed between excised breast tissue volume and initial seroma size (r_s = 0.431, p < 0.05). Fractionation schedule had no significant impact on seroma volume reduction.

At a median follow-up of 18.7 months (range: 4.0–30.4 months), 60% of seromas (15/25) had fully resolved, with a median resolution time of 10.7 months postoperatively (range: 6.1–21.7 months). 7 patients developed tumor bed induration after one year, which was independent of seroma resolution. Suspected recurrent lesions were observed in 6 patients (24%) at the tumor bed; 4 underwent core needle biopsy due to inconclusive breast ultrasound findings, with all cases confirming no definitive recurrence.

Conclusion: Seroma volume undergoes significant reduction during WBRT, with most cases resolving within the first postoperative year. While initial seroma size is influenced by tumor and surgical factors, it does not predict long-term resolution. The evolving nature of seroma can complicate recurrence detection, highlighting the need for cautious interpretation to avoid unnecessary interventions.