Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_4_3356 - Improving Reproducibility and Inter-Rater Reliability for Lumpectomy Cavity Boost Contouring in Breast Cancer Patients Using a 3-D Bio-Absorbable Tissue Marker

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Improving Reproducibility and Inter-Rater Reliability for Lumpectomy Cavity Boost Contouring in Breast Cancer Patients Using a 3-D Bio-Absorbable Tissue Marker
M. Abugideiri1, R. H. Press1, C. Zhang2, M. Thomas1, S. Tian3, J. Jhaveri1, R. J. Cassidy III1, D. Zaenger1, T. Morgan1, N. A. Madden4, J. Parks1, Z. S. Buchwald1, D. Morrison5, Z. Chen6, Y. Robertson7, R. Phillips7, J. C. Landry3, and K. D. Godette1; 1Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, 2Department of Biostatistics and Bioinformatics Shared Resource, Winship Cancer Institute of Emory University, Atlanta, GA, 3Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA, 4Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, GA, 5Emory University, Atlanta, GA, 6Department of Bioinformatics and Biostatistics, Winship Cancer Institute of Emory University, Atlanta, GA, 7Metro Surgical Associates, Atlanta, GA

Purpose/Objective(s): The accurate delineation of the lumpectomy cavity (LC) after breast conserving surgery (BCS) is critical to direct the high dose radiation boost, as it is the region at highest risk for failure. Defining the LC is traditionally guided by the post-operative seroma, anatomical landmarks, and/or surgical clips. In the setting of oncoplastic reduction (OR), however, this process can be challenging and often results in an overestimation of the LC. This study seeks to evaluate whether the use of a novel 3-D implantable tissue marker (TM) will improve reproducibility of the LC delineation and result in smaller, more accurate, LC volumes.

Materials/Methods: The records of 20 consecutive patients (range: 41-76 years) who underwent BCS followed by adjuvant radiation therapy with a LC boost at our institution between January 2015 and October 2017 were reviewed. Eight patients underwent BCS alone (40%), and 12 underwent BCS with OR (60%). All patients had a 3-D TM placed at the time of surgery. Ten independent radiation oncologists determined the LC boost volume in two ways: 1) the anatomic cavity (AC) was defined using traditional indicators such as the seroma and surgical clips, and 2) the TM cavity (TMC) was defined using the 3-D TM as a guide. All LC volumes were then compared to the reference LC contour initially approved for treatment. A paired T-test and the generalized estimating equation models were used for statistical analysis.

Results: The mean LC volume was significantly larger in the AC arm (33.2cc, standard deviation [SD]=29.2) using traditional LC indicators compared to the TMC arm (13.2cc, SD=13.8) (p<0.001) using the 3-D TM as a guide. The mean volume of the reference LC used for treatment planning was 11.8cc. The percent overlap between the reference LC and the AC arm was significantly less (52%) than the percent overlap between the reference LC and the TMC arm (84%) (p<0.001). The mean Dice similarity coefficient (DSC) in the AC arm was 0.58 and 0.66 in the BC arm (p=0.056). The mean Pearson correlation coefficient (PCC) was 0.4488 in the AC arm and 0.5798 in the BC arm. For those undergoing OR, the mean DSC in the AC arm was 0.56 and 0.68 in the BC arm.

Conclusion: Using a 3-D TM as a guide trended to improve inter-rater reliability among physicians and facilitated more precise and accurate LC volumes relative to the reference LC volume. Using a 3-D TM appeared to help improve consistency among radiation oncologist-defined boost volume contours and can result in smaller, more accurate LC volumes as compared to conventional methods.

Author Disclosure: M. Abugideiri: None. R.H. Press: None. C. Zhang: None. M. Thomas: None. S. Tian: None. R.J. Cassidy: None. N.A. Madden: None.

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