Combined Application of Technetium-99m Sulfur Colloid and Blue Dye for Sentinel Lymph Node Detection in Early-stage Breast Cancer

Summary

This article describes in detail the protocol of sentinel lymph node (SLN) mapping with combined application of technetium-99m sulfur colloid (^99mTc-SC) and methylene blue, including the preparation of ^99mTc-SC, drug injection, image acquisition and reconstruction, methylene blue mapping, and intraoperative localization of SLNs.

Abstract

Sentinel lymph node biopsy (SLNB) is the standard procedure for axillary lymph node staging in breast cancer patients, and its application has prevented unnecessary axillary lymph node dissection (ALND) in early-stage breast cancer in the past decades. Accurate sentinel lymph nodes (SLNs) localization helps improve the success rate of SLNB. The dual-tracer technique (radiocolloid plus blue dye) for SLN mapping significantly improves the identification rate compared to single tracer methods. The most widely adopted radiocolloid is ^99mTc-SC, and methylene blue is widely used in visual mapping. However, previous studies have found that the identification rate of SLN imaging varies significantly, which may be closely related to the preparation process and the operator's experience.Standardization of the SLN mapping protocol is crucial for maximizing the identification rate and minimizing false-negative results. This article provides a detailed process using ^99mTc - SC combined with methylene blue for SLN mapping in early-stage breast cancer, including procedures for the preparation of ^99mTc-SC, injection, SLN image acquisition, methylene blue mapping and intraoperative localization.

Introduction

In early-stage breast cancer, only a minority of cases present with axillary lymph node metastasis. For these patients, axillary lymph node dissection (ALND) does not provide additional survival benefits and may lead to severe complications such as upper limb lymphedema^1,2. The sentinel lymph node (SLN) is defined as the "first-station" lymph node receiving lymphatic drainage from the breast tumor³. If the SLN shows no metastasis, the probability of metastasis in downstream lymph nodes is extremely low⁴. According to the 2021 guidelines titled Managem....

Protocol

This study was approved by the Clinical Research Approval Committee of the First Affiliated Hospital, Zhejiang University School of Medicine [2025B] IIT Ethics Approval No.0125. Written informed consent was obtained from all subjects. The entire synthesis procedure must be conducted inside a fume hood. The lead glass panel of the hood provides shielding against radiation, while its negative pressure airflow design prevents the dispersion of radioactive aerosols or volatiles, thereby avoiding inhalation by personnel. Dispose of vials, syringes, and needles in a ^99mTc radioactive waste container in accordance with relevant regulations. Other materials should ....

Results

We successfully synthesized ^99mTc-SC with RCP > 92%, the curve of RCP is shown in Figure 2. We obtained high-quality SLN mapping of ^99mTc-SC to detect SLNs in early-stage breast cancer patients (Figure 4). Methylene blue mapping was helpful for the rapid localization of SLNs during operation (Figure 5). The SLNs were finally identified by a γ-ray detector, avoiding the omission of SLNs in the axillary .......

Discussion

In this study, the combined use of preoperative ^99mTc-SC and intraoperative methylene blue achieved a 99.8% identification rate of SLN, while radiocolloid alone demonstrated a similarly high rate of 99.1%. Thus, surgeons can achieve near-optimal SLN detection rate using radiocolloid alone. However, in cases that radiocolloid mapping failed, methylene blue helped the SLN detection, which aligns with previous SLN mapping studies^9,18,

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.9% saline	China Otsuka Pharmaceutical Co.,Ltd.	24a75B3	Dilution solution
Acrodisc Syringe Filter	PALL	PN4612	0.2 μm Supor Membrane
chromatography paper	Cytiva	09927854	For radiochemical purity analysis
Fume hood	Qingdao Qingdun Medical Technology Co., Ltd.	20150710	Radiation protection in drug synthesis
Glass Spotting Capillary	Sinopharm Chemical Reagent Co.,LtD	20250510	Sample the injection for radiochemical purity analysis
Lead shield	Suzhou Hengkang Medical Devices Co.,Ltd	5mm Pb	Radiation protection in injection
Medical disposable sterilization rubber gloves	Sri Trang Gloves (Thailand) Public Company Limited	F840	Protects hands from contamination.
Methanol	Huzhou Shuanglin Chemical Technology Co.,LtD	20251021	For radiochemical purity analysis
Methylene Blue	Jumpcan Pharmaceutical Co.,Ltd.	240812	Intraoperative Methylene Blue mapping and SLN identification
MiniGita radioactive TLC thin layer scanner	Sepate Technology Co., LtD		TLC for radiochemical purity
needle	Jiangsu Kangbao Medical Equipment Co., Ltd.	20240722	4.5-gauge (26 G)
Neoprobe Gamma Detection System (GDS)	Mammotome	2331609	Intraoperative Sentinel lymph nodes detection
PH test paper	Sinopharm Chemical Regent  Co.,LtD	72002361	range:1-14
SPECT/CT	GE Health Care	Discovery NM/CT 670	Image Acquisition
syringe	Zhejiang Longde Pharmaceutical Co., Ltd.	202404004, 202412014	1 mL, 5 mL
technetium-99m	Beijing Atom High-Tech Co.,Ltd.	241020-111	It should be eluted from a Mo-Tc generator within 24 h, and it must be free of oxidizing agents.
Vial A	Beijing Shihong Pharmaceutical Co., Ltd.	241020	2.0 mL of 0.15 mol/L hydrochloric acid (HCl)
Vial B	Beijing Shihong Pharmaceutical Co., Ltd.	241020	2.0 mL of a buffer solution composed of 49.2 mg of sodium dihydrogen phosphate (NaH2PO4) and 15.8 mg of sodium hydroxide (NaOH).
Vial C	Beijing Shihong Pharmaceutical Co., Ltd.	241020	lyophilized product containing a white, water-soluble powder composed of 2.0 mg of sodium thiosulfate (Na2S2O3), 2.3 mg of disodium edetate (Na2EDTA), and 18.1 mg of gelatin
Xeleris workstation	GE Health Care	Imaging software	Process images to generate planar and fused SPECT/CT datasets, Localize SLNs