Neoadjuvant chemotherapy for advanced breast cancer has led to an increased rate of breast-conserving surgery (BCS) in these patients. As the demand for preoperative localization methods grows among surgeons performing BCS, traditional localization techniques have shown limitations. For non-palpable breast lesions, preoperative localization has commonly been achieved using ultrasound-guided skin markings or needle localization. However, these methods present challenges, including difficulty in depth localization for patients with large breasts and limitations in real-time re-verification during surgery due to air artifacts after incision. Needle localization, although commonly used, is invasive and poses risks such as displacement or detachment of the needle.

Indocyanine green (ICG), a fluorescent dye that appears green to the naked eye and is detectable by near-infrared (NIR) cameras, has been widely and safely used in clinical practice via intravenous or subcutaneous administration. Recently, ICG combined with NIR imaging has been adopted for sentinel lymph node biopsy in breast cancer and melanoma surgeries and is increasingly used as a localization method for various tumors, replacing conventional techniques.

A preliminary study (IRB No. NCC2016-0071) conducted at the institution evaluated ICG injection and NIR fluorescence imaging for tumor localization in early breast cancer patients undergoing BCS. The study demonstrated the efficacy of ICG-based localization in reducing the rate of positive surgical margins.

The objective of this study is to evaluate the effectiveness of ICG-guided tumor localization with NIR fluorescence imaging in patients with advanced breast cancer treated with neoadjuvant chemotherapy. It is hypothesized that this technique will allow for more accurate tumor excision compared to conventional methods, ultimately improving surgical outcomes.

Inclusion Criteria:

• The Patient with locally advanced breast cancer who is eligible for breast-conserving surgery after receiving neoadjuvant chemotherapy
• Aged over 18 years old
• ECOG performance status: 0 or 1
• The patients with written informed consent

Exclusion Criteria:

• The patient who requires total mastectomy after receiving neoadjuvant chemotherapy
• The patient with no residual mass on ultrasonography or only with microcalcifications
• Pregnant or lactating patient
• The patient with a disability to understand and provide consent
• The patient with severe allergic history to indocyanine green
• Iodine-sensitive patient