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 cm(3)). 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.