Abstract P6-03-09: Internal mammary lymph node biopsy during free flap breast reconstruction: Accurate oncologic staging leads to change in adjuvant therapies

Abstract

Abstract Introduction: Accurate breast cancer staging, including nodal status, is essential for optimal management of adjuvant therapies leading to improved disease-specific and overall survival. Lymphatic drainage of the breast is known to involve both axillary and internal mammary (IM) lymph node basins. While IM nodal metastases represent advanced cancer stage, sampling is not routinely advocated due to relative lack of accessibility and the assumption that IM node positivity rarely alters adjuvant therapies. The current study analyzes the incidence of IM nodal metastases sampled during routine IM vessel exposure for free flap breast reconstruction and changes in adjuvant treatment. Methods: A retrospective analysis of patients with positive IM lymph node biopsies at the time of free flap breast reconstruction following mastectomy between September 2008 and December 2015 was performed. Patients undergoing reconstruction following prophylactic mastectomy and reconstruction where IM vessels were not exposed were excluded. Prevalence of neoadjuvant therapies and previous lumpectomy with axillary lymph node (LN) sampling were recorded. Tumor size, location, and axillary LN status were obtained from final pathologic analysis. Prognostic factors and proliferative index (Ki-67) for the primary breast lesion were utilized to determine oncologic subtype. Change in adjuvant therapies (chemotherapy or external beam radiation) based solely on IM LN positivity was calculated. Results: During the study period, 2057 patients fit study criteria. Twenty eight (1.3%) patients were found to have IM LN metastases and comprised the study population. Mean age of patients with positive IM metastases was 49 years with pre-reconstruction chemotherapy or radiation administered in 50% or 54% of cases, respectively. Five (18%) patients had previously undergone lumpectomy with axillary sampling prior to mastectomy and reconstruction for cancer recurrence. Mean tumor size was 3.1 cm (range 0.4 to 10 cm) with tumor location evenly distributed among all four quadrants. Although statistical significance between subtypes was not identified, luminal B (42.9 percent) was the most common subtype present. Ten (36%) patients had isolated IM lymph node metastases with negative axillary nodal disease. Patients with both axillary and internal mammary disease had larger lesions (4.4 cm vs. 2.5 cm), increased prevalence of pre-reconstruction chemotherapy (65 percent vs. 20 percent) and radiation (71 percent vs. 20 percent). Multivariate analysis did not identify any significant independent factors associated with isolated IM lymph node metastases. Ultimately, 17 (63%) patients had a change in their adjuvant therapy (additional chemotherapy or IM radiation therapy) based on positive IM LN disease. Conclusion: Despite the low overall incidence of IM LN metastases, IM LN biopsy at the time of free flap breast reconstruction is recommended. In 36% of cases, nodal metastases were isolated to the IM nodes. Interestingly, a significant percentage (18%) of patients had previously undergone lumpectomy and axillary sampling. Identification of IM metastases significantly influenced adjuvant therapies in a majority of cases. Citation Format: Ochoa O, Pisano S, Chrysopoulo M, Ledoux P, Arishita G, Nastala C. Internal mammary lymph node biopsy during free flap breast reconstruction: Accurate oncologic staging leads to change in adjuvant therapies [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-09.