P3-07-15: Sequential Peri-Areolar and Peri-Tumoural SPECT/CT Lymphoscintigraphy Has Identified High Rates of Discordance in Both Axillary and Internal Mammary Sentinel Lymph Node Mapping.

Abstract

Introduction: The release of the MA20 intergroup trial results has confirmed the importance of locoregional radiation on local and distant disease control and survival. Sentinel lymph node (SLN) evaluation is the gold standard for regional lymph node evaluation and radiation oncologists continue to utilize the nodal staging to plan adjuvant locoregional therapy. Despite over a decade of experience in SLN evaluation there persists a common belief that the lymphatic drainage of the whole breast is to anteropectoral axillary lymph nodes. Several different lymphoscintigraphy injection techniques are in use with claims that they all identify the same axillary sentinel nodes. However this is not based on a high level of evidence. The evolution of SPECT/CT has led to the accurate anatomic identification of SLN, hence the different lymphoscintigraphy techniques can now be directly compared. Method: 38 patients underwent double sequential lymphoscintigraphy (peri-areolar followed by peri-tumoural) separated by 1–7 days. Patients were referred by 4 surgeons to 3 separate lymphoscintigraphy centres with standardisation of tracer substance (99mTc-antimony sulfide colloid), lymphoscintigraphy and SPECT/CT evaluation techniques. The degree of discordance in sentinel node evaluation was defined as: Type 1 - One study demonstrates SLN(s) in a nodal basin [axilla or internal mammary chain (IMC)] and the other study demonstrates none. Type 2 - Both studies identified SLN(s) in a nodal basin however the SLN(s) are all different. Type 3 - Both studies identified SLNs in a nodal basin, however some SLN(s) are identical and others not. Results: Notably 21 patients (55%) had either axilla or IMC lymphoscintigraphy discordance. Two patients had both axilla and IMC lymphoscintigraphy discordance. The majority of discordance was identified in the IMC. In the concordant IMC lymphoscintigraphies neither study demonstrated IMC SLN. There were no studies that identified identical IMC nodes in both PA and PT lymphoscintigraphy. Discordant axillary drainage was more evident in patients with lateral sector tumours compared to IM discordance with medial sector tumours. Conclusions: Accurate lymphoscintigraphy is the road map to assist a surgeon identify lymph node metastases. In turn accurate staging will determine appropriate adjuvant therapy decisions particularly regional node irradiation. This study demonstrates a high degree of discordance between PA and PT lymphoscintigraphy techniques in 55% of patients. Inadequate lymphoscintigraphy can result in unrealized false negative results, which could impact patient outcomes and clinical trial results. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-15.