Abstract PS14-21: Refining loco-regional therapy for inflammatory breast cancer protocol in progress

Background: Inflammatory breast cancer (IBC) is the most aggressive locally advanced breast cancer subtype. It is associated with loco-regional recurrence rates of 12-25%, and neoadjuvant chemotherapy (NAC) followed by modified radical mastectomy and comprehensive chest wall and regional nodal radiotherapy remain the standard of care. As has been demonstrated in non-IBC, achievement of pathologic complete response (pCR) has been shown to be associated with improved loco-regional control, recurrence-free and overall survival. Advances in NAC for IBC have resulted in improved pCR rates in both the breast and the axilla, with overall axillary pCR rates of approximately 30%, reaching as high as 67% in patients with HER2-positive disease receiving HER2-directed therapy. Hypothesis: Sentinel lymph node biopsy (SLNB) may be feasible in IBC patients who experience a good clinical and pathologic response in the axilla to NAC. Primary Objective: To evaluate the sentinel lymph node (SLN) identification rate in stage III IBC patients who experience cN0 status at completion of NAC. Secondary Objective: To assess the incidence of lymphedema following standard local-regional therapy for IBC. Methods and Study procedures: In this feasibility study, 50 patients with cT4dN0-2M0 IBC will be enrolled in order to evaluate 40 patients whose axillary nodal status becomes cN0 upon completion of NAC. All patients will undergo a research breast biopsy and lymphoscintigram pre and post NAC to evaluate lymphatic drainage patterns and patency of breast and axillary lymphatics. Post NAC lymphoscintigraphy will be appropriately timed for pre-operative SLN mapping and all patients will undergo SLNB using dual tracers (Tc99 Sulfur colloid and blue dye) with immediate axillary lymph node dissection (ALND), at the time of mastectomy. The patient-reported Lymphedema Symptom Intensity and Distress Survey (LSIDS-A) will be collected at 6 timepoints. Patients will be followed for 2 years post-surgery for oncologic outcomes. Correlatives: We plan to evaluate genetic and phenotypic heterogeneity in IBC and to assess markers of angiogenesis and lymph-angiogenesis associated with IBC, as well as to explore immunologic aspects of the tumor microenvironment and their association with pCR. Statistics: The identification rate will be calculated as number of patients in whom SLNs were successfully identified over the number of patients with cN0 disease after NAC in whom SLN mapping was attempted. Using a Simon two-stage design (α=.10, β=.10), a SLN identification rate of ≥90% would result in considering this procedure feasible whereas an identification rate of ≤75% (null hypothesis) would lead to the conclusion that it is not feasible. In the first stage, if greater than 18 of 25 patients have SLNs identified, then a total of 40 patients will be enrolled. If fewer than 33 of 40 patients have SLN identified, then the null hypothesis is rejected. Citation Format: Faina Nakhlis, Meredith Regan, Heather Jacene, Beth Harrison, Jennifer Bellon, Jean Landry, Eren Yeh, Elizabeth Mittendorf, Beth Overmoyer, Tari King. Refining loco-regional therapy for inflammatory breast cancer protocol in progress [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS14-21.