Clinical Factors Associated With Seroma Volume Reduction in Breast-Conserving Therapy for Early-Stage Breast Cancer: A Multi-Institutional Analysis

Purpose To correlate clinical factors with seroma volume and reduction; and to determine whether cone-beam CT (CBCT) could be used clinically to monitor seroma reduction. Patients and Methods This investigation included 102 women from five institutions with stage T1–2 breast cancer treated with breast-conserving therapy. Two CT scans were acquired: the planning CT (CT1) and a second CT (CT2) during radiotherapy (RT). Seroma was contoured on all scans, and correlations between seroma characteristics and clinical factors were investigated by univariate and multivariate analyses. In a substudy, 10 of the 102 patients received multiple CBCT scans during RT. Seroma were contoured by two observers in the substudy. Fifteen time points at which CT and CBCT were performed within 2 days were identified. The levels of correlation in seroma contours between CBCT and CT and between the two observers were examined. Results The mean relative seroma reduction from CT1 to CT2 was 54% ( p < 0.001). A significant inverse relationship was found between relative seroma reduction per week and number of RT fractions given by univariate and multivariate analyses ( p = 0.01, 0.03). The mean difference in contoured seroma volumes between CT and CBCT was 12% (3.3 cm3 ). When assessing the relative difference in seroma contours between Observer 1 and Observer 2, an interobserver difference of 12% was demonstrated. Neither discrepancy was clinically significant. Conclusions Radiotherapy seems to hinder seroma reduction. Volume discrepancies between CBCT and CT were minor, with low interobserver variation, indicating that CBCT might be useful in monitoring seroma reduction.