Abstract P3-03-06: Internal mammary chain sentinel nodes in early stage breast cancer patients: Towards selective removal
Authors: AA van Loevezijn, SA Bartels, FH van Duijnhoven, WD Heemsbergen, SC Bosma, PH Elkhuizen, ML Donswijk, EJ Rutgers, HS Oldenburg, M-JT Vrancken Peeters, IM van der Ploeg
Journal: Cancer Research (2019)

Abstract Background Internal mammary chain (IMC) sentinel nodes (SN) are visible in 1 out of 5 breast cancer patients on lymph scintigraphy after intra- or peritumoral injection of a radiopharmaceutical. The IMC SN status affects prognosis and treatment of breast cancer and IMC radiotherapy improves survival in selected patients. In contrast to the axillary SN, removal of the IMC SN is not routinely performed and often technically challenging. This study aims at determining the effect of IMC SN biopsy on recurrence-free survival (RFS) and overall survival (OS) and the identification of predictive factors for the development of IMC- and distant metastases. Methods All patients with IMC SNs were selected from a prospective database from 1999 to 2007. Following intratumoral injection of technetium-99m, conventional lymphoscintigraphy was performed. Sentinel nodes were removed in all regions with lymphatic drainage on scintigraphy. The RFS and OS were calculated for the total group and subgroups with tumor-positive, tumor-negative or non-removed IMC SN. Predictive factors were identified for tumor-positive IMC SN and for distant metastasis by regression analysis. Results Internal mammary chain SN biopsy was performed in 287 out of 336 patients (85%). The IMC SN was tumor-positive in 38 patients (13%). Patients with IMC metastasis had poorer OS compared to patients without IMC metastasis or a non-removed IMC SN (57%, 82% and 59% 10- year OS, respectively, p = 0.002). These patients also had worse RFS, mainly due to by the development of distant metastases (68%, 84% and 61% RFS, respectively, p = 0.002). Multivariable predictive for tumor-positive IMC SN were axillary metastases (PPV = 38.5%). Predictive factors for distant metastasis were tumor-positive IMC SN (HR 2.5, 95% CI; 1.0 - 5.8, p = 0.04), not removed IMC SN (HR 2.3, 95% CI; 1.0 - 5.1, P = 0.05), tumor diameter &amp;gt;1.5cm (HR 3.5, 95% CI; 1.6 - 8.4, p &amp;lt; 0.00) and age &amp;gt;65 years (HR 3.1, 95% CI; 1.2 - 7.7, p = 0.02, reference &amp;lt;50 years). Conclusion Breast cancer patients with tumor-positive IMC SN have worse 10- year survival than patients with tumor-negative IMC SN, mainly due to the development of distant metastasis. The clinically relevant predictive factor for distant metastasis is tumor size &amp;gt;1.5cm. Radiotherapy of the IMC can improve survival. However, the cardiotoxicity of parasternal radiotherapy must be weighed against the expected survival benefit. Therefore, our current protocol is to perform IMC SN biopsy in patients younger than 70 years with a tumor diameter &amp;gt;1.5cm. Citation Format: van Loevezijn AA, Bartels SA, van Duijnhoven FH, Heemsbergen WD, Bosma SC, Elkhuizen PH, Donswijk ML, Rutgers EJ, Oldenburg HS, Vrancken Peeters M-JT, van der Ploeg IM. Internal mammary chain sentinel nodes in early stage breast cancer patients: Towards selective removal [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-06.