Abstract PD4-05: Axillary recurrence is a rare event in node-positive patients. treated with sentinel node biopsy alone after neoadjuvant chemotherapy: Results of a prospective study

Abstract

Abstract Background: Four prospective multi-institutional trials have demonstrated that clinically node-positive patients (cN1) who receive neoadjuvant therapy (NAC) and convert to cN0 can be reliably staged with sentinel lymph node biopsy (SLNB) with false-negative rates (FNRs) of < 10%, when ≥ 3 SLNs are retrieved. Since study patients all had axillary lymph node dissection (ALND), the rate of axillary recurrence after SLNB alone is unknown. Of concern is the possibility that residual chemotherapy-resistant axillary disease could lead to higher recurrence rates than seen in the primary surgery setting for cN0 patients where SLN FNRs of 5-10% result in axillary recurrence in < 1% of cases. Here we report regional recurrence rates in a prospectively defined cohort of cN1 patients receiving NAC, followed by a negative SLNB using a standardized technique, and no further axillary surgery. Methods: From 06/2014 to 02/2019, patients with cT1-3 biopsy-proven cN1 breast cancer who received NAC and converted to cN0 by physical exam were prospectively managed with SLNB with dual tracer mapping and omission of ALND if ≥ 3 SLNs were pathologically negative. Nodes were not routinely clipped, and retrieval of clipped metastatic nodes was not required. Pathologically negative SLNs were defined as the absence of any metastases including isolated tumor cells. Results: Of 610 cN1 patients treated with NAC, 555 (91%) converted to cN0 and had SLNB; 234 (42%) had ≥ 3 negative SLNs and were treated with SLNB alone. Median patient age was 49 years and median tumor size at presentation was 3 cm; 61% were HER2+ and 18% triple negative. Most (91%) received doxorubicin-based NAC and 88% received adjuvant radiotherapy (RT), with 80% (n = 164) of RT patients receiving nodal RT (Table). At a median follow-up of 35 months, there was only 1 (0.4%) axillary recurrence for the entire cohort, synchronous with a breast recurrence, in a patient who refused RT. Among patients who received RT (n = 205), there were no axillary recurrences. The 4-year rate of distant recurrence for all patients was 6.1% (95% CI, 3.4-10.7%) and 4-year overall survival was 93.9% (95% CI, 87.6-97.1%). Conclusion: In cN1 patients treated with NAC, rates of axillary recurrence in patients with ≥ 3 pathologically negative SLNs treated with SLNB alone were low, without routine nodal clipping. Although further follow-up is needed, multiple studies have shown that nodal recurrence is an early event, particularly in HER2+ and triple negative patients, who comprised the majority of the population. Our findings support omitting ALND in cN1 patients after NAC when the SLNs are negative using an optimal SLNB technique. Table. Patient PopulationOverall cohort (n = 234)Age, years (median, IQR)49 (40, 58)Tumor size at presentation, cm (median, IQR)3.0 (2.2, 5.0)Number SLNs retrieved (median, IQR)4 (3, 5)Palpable nodes at presentation (n, %)179 (76%)HistologyDuctal211 (90%)Lobular and mixed7 (3%)Micropapillary and mixed10 (4%)Other3 (1%)Occult3 (1%)DifferentiationWell1 (0.5%)Moderate36 (15%)Poor196 (84%)Unknown1 (0.5%)Receptor StatusHR+/HER2-47 (20%)HR+/HER2+80 (34%)HR-/HER2+64 (27%)HR-/HER2-43 (18%)Breast SurgeryBCS118 (50%)Mastectomy116 (50%)Breast pCR¥Yes161 (70%)No70 (30%)NAC regimenAC-T197 (84%)AC-T + carbo15 (6.4%)TC8 (3.4%)Other14 (6%)Neoadjuvant anti-HER2 treatmentHP (dual-therapy)144 (100%)Adjuvant RTYes205 (88%)No*29 (12%)¥3 patients had occult primary breast cancer and were not included in breast pCR calculation; *6/29 patients who did not receive RT enrolled in NSABP B-51 Citation Format: Andrea V Barrio, Giacomo Montagna, Anita Mamtani, Varadan Sevilimedu, Hiram S Cody, III, Mahmoud El-Tamer, Mary L Gemignani, Alexandra S Heerdt, Tracy-Ann Moo, Melissa Pilewskie, George Plitas, Lisa Sclafani, Kimberly J Van Zee, Monica Morrow. Axillary recurrence is a rare event in node-positive patients. treated with sentinel node biopsy alone after neoadjuvant chemotherapy: Results of a prospective study [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 PD4-05.