Catheter-based delineation of lumpectomy cavity for accurate target definition in partial-breast irradiation with multicatheter interstitial brachytherapy

Abstract

Purpose: In partial-breast irradiation (PBI), accurate lumpectomy cavity (LC) delineation is critical. Seroma-based delineation (SBD) using computed tomography (CT) with clips remains uncertain, causing an expansion of the LC and planning target volume (PTV). In catheter-based delineation (CBD), the implanted catheters were used as reference markers for LC delineation in multicatheter interstitial brachytherapy (MIB). Material and methods: Between October 2008 and October 2018, 513 patients who underwent MIB-PBI were examined. In CBD, anatomical relations of LC to catheters were recorded. In randomly selected 22 CBD cases, the LC volume and PTV were retrospectively recontoured on SBD, and the relationship between the contribution of CBD and cavity visuality was evaluated. The LC volume and PTV before and after the introduction of CBD were compared. Results: The mean LC volumes based on SBD and CBD were 19.1 cm 3 and 14.1 cm 3 , respectively (p < 0.001). The mean PTVs based on SBD and CBD were 47.9 cm 3 and 35.7 cm 3 , respectively (p < 0.0001). More reductions in the LC volume (5.1 cm 3) (p < 0.05) and PTV (7.7 cm 3) (p = 0.13) were observed in the poorly visible LC than in the visible LC. The LC volume and PTV before the introduction of CBD (n = 411) were compared with those after introduction (n = 102). Significant reductions were observed in the LC volume (5.9 cm 3) (p < 0.0001) after the introduction of CBD; moreover, PTV tended to be reduced (3.9 cm 3) (p = 0.17). Conclusions: CBD may help to establish the standardized procedure for MIB-PBI and prevent unnecessary radiation exposure to the normal breast tissue.

Impact of the Delineation Accuracy of Lumpectomy Cavity on Planning Target Volume in Partial-Breast Irradiation Using Brachytherapy and External-Beam Radiotherapy

“…Both accuracy indexes were related to the LC accuracy. Among various clinical features, the clear identification of the LC had the most influence on the accuracy of PTVs 16,17,18,36 , but 66% of the patients had three or more CVS in this population. There are several methods to minimize uncertainties reported including the reference of preoperative CT, magnetic resonance imaging-based delineation, clip insertion, and tissue marker insertion.…”

“…29,30 Although a smaller target volume was crucial to achieving better cosmesis, an uncertain target delineation on unclear LC tended to be delineated larger than on clear demarcation to avoid the geographic miss. 17,31 Therefore, an accurate target delineation is crucial to achieving not only tumor control but also potential improvement of cosmetic outcomes in PBI.…”

“…During surgery for MIB-PBI, the distances between upper and lower edges of the glandular tissue and needles and from the point of the bottom of each catheter to the cavity walls were measured using the catheter-based delineation technique, which was put into the CT image as an additional piece of information to the CT image with clips. 17 As a conventional delineating technique for this study, one radiation oncologist (N.N.) and one radiation technician (T.S.)…”

“…16 In our institution, perioperative MIB-PBI has been performed using the intraoperative catheter implant, of which the LC on catheter-based delineation has been reported as accurately as possible because of the usage of the implanted catheters as fiducial markers. 17,18 In this study, the LC was delineated on CT with clips as a conventional method compared with that on catheter-based delineation as a reference. The different PTV definitions assumed to perform brachytherapy-based PBI and EBRT-PBI have been developed to evaluate the target accuracy, and the impact of the delineating accuracy of the LC on the PTVs has also been assessed.…”

Predicting adherence of dose–volume constraints for personalized partial-breast irradiation technique

“…Between October 2008 and April 2020, 653 patients received BCT using MIB-PBI, and the clinical and imaging data from the consequent 159 patients receiving MIB-PBI after September 2018 were extracted in the study. The MIB-PBI indications and techniques used at our institution have been reported previously (22,23). In brief, enrollment criteria included patients aged $40 years old, maximal tumor diameter #3.0 cm, negative metastases of sentinel nodes, and a negative surgical margin as assessed by specimen mammography.…”