Abstract
BackgroundTo investigate the patterns of post-lumpectomy seroma volume (SV) change and related clinical factors to determine the benefits of adaptive planning in magnetic resonance imaging (MRI)-guided partial breast irradiation (PBI).MethodsMRI data obtained from 37 women with early breast cancer acquired at simulation and at the 1st, 6th, and 10th fractions were analyzed. The planning target volume (PTV) was defined as unequal margins of 10–15 mm added according to the directional surgical margin status of each seroma. Treatment was performed using a 0.35 T MRI-guided radiotherapy system. Univariate analysis was performed to assess the correlations between SV change rate and clinical factors. Seroma and PTV for adaptive planning were based on the images obtained at the 6th fraction.ResultsThe average time intervals between surgery-simulation, simulation-1st, 1st-6th, and 6th-10th fractions were 23.1, 8.5, 7.2, and 5.9 days, respectively. Of the 37 patients, 33 exhibited decreased SV over the treatment period. The mean SV of these 33 patients decreased from 100% at simulation to 60, 48, and 40% at each MRI scan. In most cases (26/33), the logarithm of SV was inversely proportional to the elapsed time from surgery (R2 > 0.90, Pearson’s correlation test). The volume of spared normal tissue from adaptive radiotherapy was proportional to the absolute change in SV (R2 = 0.89, Pearson’s correlation test).ConclusionSeromas exhibit exponential shrinkage over the course of PBI. In patients receiving PBI, frequent monitoring of SV could be helpful in decision-making regarding adaptive planning, especially those with a large seroma.
Highlights
To investigate the patterns of post-lumpectomy seroma volume (SV) change and related clinical factors to determine the benefits of adaptive planning in magnetic resonance imaging (MRI)-guided partial breast irradiation (PBI)
From October 2015 to July 2016, 55 patients received PBI and 38 patients developed a well-defined post-lumpectomy seroma, including one patient with a seroma lying from the primary site to an axillary region, which was, in part, believed to be generated from a sentinel node biopsy and was excluded from the analysis
The seroma was located in the upper-outer, upper-inner, lower-outer, and lower-inner quadrant of the breast in 12, 18, 6, and 1 patients, respectively
Summary
To investigate the patterns of post-lumpectomy seroma volume (SV) change and related clinical factors to determine the benefits of adaptive planning in magnetic resonance imaging (MRI)-guided partial breast irradiation (PBI). Based on the spatial pattern of recurrence, partial breast irradiation (PBI) can be introduced as an alternative to conventional whole-breast irradiation followed by boost in selected patients with early breast cancer, aiming for a short treatment time. In PBI, defining the optimal target volume is crucial to thoroughly cover the area at risk and to simultaneously minimize toxicity. The target volume of PBI is defined as tissues surrounding the tumor bed [8]. Seroma volume (SV) is well-known to typically shrink with time [11,12,13,14,15,16,17]. An ideal target volume should differ in each PBI
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