Definition of Internal Mammary Node Target Volume Based on the Position of the Internal Mammary Sentinel Lymph Nodes Presented on SPECT/CT Fusion Images

Xue Wang; Wei Wang; Jian-Bin Li; Zong-Wei Huo; Min Xu; Peng-Fei Qiu; Ying-Jie Zhang; Feng-Xiang Li; Jin-Zhi Wang

doi:10.3389/fonc.2019.01553

Definition of Internal Mammary Node Target Volume Based on the Position of the Internal Mammary Sentinel Lymph Nodes Presented on SPECT/CT Fusion Images

Front Oncol. 2020 Jan 31:9:1553. doi: 10.3389/fonc.2019.01553. eCollection 2019.

Authors

Xue Wang^{1

2}, Wei Wang², Jian-Bin Li², Zong-Wei Huo³, Min Xu², Peng-Fei Qiu⁴, Ying-Jie Zhang², Feng-Xiang Li², Jin-Zhi Wang²

Affiliations

¹ School of Medicine and Life Sciences, University of Jinan-Shandong Academy of Medical Sciences, Jinan, China.
² Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.
³ Department of Nuclear Medicine, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.
⁴ Department of Breast Surgery, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.

Abstract

Purpose: Mapping the distribution of internal mammary sentinel lymph nodes (IM-SLNs) presented on single photon emission computed tomography in conjunction with computed tomography (SPECT/CT) images to explore the value of IM-SLN to guide tailored clinical target volume (CTV) delineation of postoperative prophylactic IMNI. Materials and methods: Ninety-seven patients who underwent preoperative lymphoscintigraphy by SPECT/CT and had imaging of IM-SLN were selected in this study. The imaging IM-SLNs on SPECT/CT of eligible patients were projected onto corresponding anatomical positions of a representative axial CT image. The IMN CTVs were delineated on the representative axial CT images according to the Radiation Therapy Oncology Group (RTOG) and Danish Breast Cancer Cooperative Group (DBCG) guideline, and defined as CTV_RTOG and CTV_DBCG. The location of the IM-SLNs was compared with the RTOG and DBCG guidelines of IMN target volume delineations, respectively. The intercostal space distribution of IM-SLNs was recorded. The distances from the CTV_RTOG and CTV_DBCG to the IM-SLNs were measured, respectively. Results: The total number of imaging IM-SLNs was 136. IM-SLNs were mostly found in the first intercostal space (40.4%), with 30.2, 24.3, 4.4, and 0.7% of IM-SLNs in the second, third, fourth, and fifth intercostal space, respectively. The average distance from the edge of the CTV_RTOG and the edge of CTV_DBCG to the central points of the IM-SLNs was 4.10 mm (SD, 3.3 mm) and 1.60 mm (SD, 2.6 mm), respectively (t = 16.640, P = 0.000). The average distance from the edge of CTV_RTOG and the edge of CTV_DBCG to the lateral border IM-SLN was 6.40 mm (SD, 3.5 mm) and 3.34 mm (SD, 3.3 mm), respectively (t = 19.815, P = 0.000). Only 18.4% of IM-SLN central points were included in the CTV_RTOG, and 60.3% of IM-SLN central points were included in the CTV_DBCG. When covering 90 and 100% of the IM-SLN center points, the CTV_RTOG needs to expand 8 and 15 mm, respectively, and the CTV_DBCG needs to expand 5 and 13 mm, respectively. Conclusion: Neither the RTOG nor DBCG consensus guideline about the delineation of IMN CTV was sufficient to cover 90% of IM-SLNs. For 90% coverage of IM-SLN central points, CTV_RTOG needed to be expanded by 8 mm, and CTV_DBCG needed to be expanded by 5 mm.

Keywords: SPECT/CT fusion image; breast cancer; clinical target volume definition; internal mammary lymph node irradiation; internal mammary sentinel lymph node.