Internal mammary lymphadenopathy in breast cancer: a narrative review and update.

Background and Objective: While the axillary nodal basin is the most common lymphatic drainage pathway of the breast, the internal mammary (IM) lymph node chain plays a significant role in breast cancer staging and treatment. It has been identified as sentinel nodal drainage in approximately 13-37% of patients. Despite this, the data is still limited with regard to diagnosis and management when there is suspicion or confirmation of IM lymph node (IMLN) involvement by metastatic breast cancer. The objective of this publication is to provide a comprehensive assessment of the current body of literature surrounding the diagnosis, management and prognostic value of IMLNs in breast cancer treatment. Methods: Review of the literature published regarding IMLN diagnosis, significance, and management was completed in PubMed. Additional focus was placed on reviewing articles published within the past 10 years as foundation for an update regarding the current practice and future directions in this space. Key Content and Findings: Improved imaging techniques, with positron emission tomography-computed tomography and magnetic resonance imaging, have led to increase in the identification of IM lymphadenopathy, yielding surgical staging of the IM nodes nearly obsolete. While IM nodal metastases may play a role in overall survival (OS), it has not been demonstrated to be an independent risk factor for increased locoregional recurrence. IM nodal irradiation (IMNI) therapy has been a mainstay in the treatment of IM disease in the context of breast cancer. IMNI has demonstrated improvement in OS and risk of distant recurrence. Wide variations in radiation practices for patients with IM lymphadenopathy exist internationally, highlighting the lack of clear data driven consensus guidelines. Conclusions: Herein, we provide an updated assessment of the current diagnosis, clinical significance, and management of IM lymphadenopathy for breast cancer patients.

Long-Term Ultrasound Twinkling Detectability and Safety of a Polymethyl Methacrylate Soft Tissue Marker Compared to Conventional Breast Biopsy Markers-A Preclinical Study in a Porcine Model.

OBJECTIVE: We have studied the use of polymethyl methacrylate (PMMA) as an alternative biopsy marker that is readily detectable with ultrasound Doppler twinkling in cases of in vitro, ex vivo, or limited duration in vivo settings. This study investigates the long-term safety and ultrasound Doppler twinkling detectability of a PMMA breast biopsy marker following local perturbations and different dwell times in a 6-mo animal experiment. METHODS: This study, which was approved by our Institutional Animal Care and Use Committee, involved three pigs and utilized various markers, including PMMA (Zimmer Biomet), 3D-printed, and Tumark Q markers. Markers were implanted at different times for each pig. Mesh material or ethanol was used to induce a local inflammatory reaction near certain markers. A semiquantitative twinkling score assessed twinkling for actionable localization during monthly ultrasounds. At the primary endpoint, ultrasound-guided localization of lymph nodes with detectable markers was performed. Following surgical resection of the localized nodes, histomorphometric analysis was conducted to evaluate for tissue ingrowth and the formation of a tissue rind around the markers. RESULTS: No adverse events occurred. Twinkling scores of all markers for all three pigs decreased gradually over time. The Q marker exhibited the highest mean twinkling score followed by the PMMA marker, PMMA with mesh, and Q with ethanol. The 3D-printed marker with mesh and PMMA with ethanol had the lowest scores. All wire-localized lymph nodes were successfully resected. Despite varying percentages of tissue rind around the markers and a significant reduction in overall twinkling (p < 0.001) over time, mean PMMA twinkling scores remained clinically actionable at 6 and 5 mo using a General Electric C1-6 probe and 9L-probe, respectively. CONCLUSIONS: In this porcine model, the PMMA marker demonstrates an acceptable safety profile. Clinically actionable twinkling aids PMMA marker detection even after 6 mo of dwell time in porcine lymph nodes. The Q marker maintained the greatest twinkling over time compared to all the other markers studied.

Neoadjuvant cobimetinib and atezolizumab with or without vemurafenib for high-risk operable Stage III melanoma: the Phase II NeoACTIVATE trial.

Both targeted therapies and immunotherapies provide benefit in resected Stage III melanoma. We hypothesized that the combination of targeted and immunotherapy given prior to therapeutic lymph node dissection (TLND) would be tolerable and drive robust pathologic responses. In NeoACTIVATE (NCT03554083), a Phase II trial, patients with clinically evident resectable Stage III melanoma received either 12 weeks of neoadjuvant vemurafenib, cobimetinib, and atezolizumab (BRAF-mutated, Cohort A, n = 15), or cobimetinib and atezolizumab (BRAF-wild-type, Cohort B, n = 15) followed by TLND and 24 weeks of adjuvant atezolizumab. Here, we report outcomes from the neoadjuvant portion of the trial. Based on intent to treat analysis, pathologic response (≤50% viable tumor) and major pathologic response (complete or near-complete, ≤10% viable tumor) were observed in 86.7% and 66.7% of BRAF-mutated and 53.3% and 33.3% of BRAF-wild-type patients, respectively (primary outcome); these exceeded pre-specified benchmarks of 50% and 30% for major pathologic response. Grade 3 and higher toxicities, primarily dermatologic, occurred in 63% during neoadjuvant treatment (secondary outcome). No surgical delays nor progression to regional unresectability occurred (secondary outcome). Peripheral blood CD8 + TCM cell expansion associated with favorable pathologic responses (exploratory outcome).

Assessment of the effect of the American Society of Breast Surgery guidelines on contralateral prophylactic mastectomy rates for unilateral breast cancer.

BACKGROUND: In July 2016, the American Society of Breast Surgeons published guidelines discouraging contralateral prophylactic mastectomy for average-risk women with unilateral breast cancer. We incorporated these into practice with structured patient counseling and aimed to assess the effect of this initiative on contralateral prophylactic mastectomy rates. METHODS: We evaluated female patients with unilateral breast cancer undergoing mastectomy at our institution from January 2011 to November 2022. Variables associated with contralateral prophylactic mastectomy and trends over time were analyzed using the Wilcoxon rank sum test or χ2 analysis as appropriate. RESULTS: Among 3,208 patients, (median age 54 years) 1,366 (43%) had a unilateral mastectomy, and 1,842 (57%) also had a concomitant contralateral prophylactic mastectomy. Across all patients, contralateral prophylactic mastectomy rates significantly decreased post-implementation from 2017 to 2019 (55%) vs 2015 to 2016 (62%) (P = .01) but increased from 2020 to 2022 (61%). Immediate breast reconstruction rate was 70% overall (81% with contralateral prophylactic mastectomy and 56% without contralateral prophylactic mastectomy, P < .001). Younger age, White race, mutation status, and earlier stage were also associated with contralateral prophylactic mastectomy. Genetic testing increased from 27% pre-guideline to 74% 2020 to 2022, as did the proportion of patients with a pathogenic variant (4% pre-guideline vs 11% from 2020-2022, P < .001), of whom 91% had a contralateral prophylactic mastectomy. Among tested patients without a pathogenic variant and patients not tested, contralateral prophylactic mastectomy rates declined from 78% to 67% and 48% to 38% pre -and post-guidelines, respectively, P < .001. CONCLUSION: Implementation of specific patient counseling was effective in decreasing contralateral prophylactic mastectomy rates. While recognizing that patient choice plays a significant role in the decision for contralateral prophylactic mastectomy, further educational efforts are warranted to affect contralateral prophylactic mastectomy rates, particularly in the setting of negative genetic testing.

Intermediate-thickness melanoma: A population-based study of surgical quality metrics.

BACKGROUND: Variability in guideline compliance for melanoma lymph node surgery is partially attributable to controversy about patient selection. Prior data has indicated suboptimal practice of sentinel lymph node biopsy and undertreatment of clinically node-positive disease, predating Multicenter Selective Lymphadenectomy Trial II publication. To minimize bias, we studied compliance with lymph node surgery guidelines in T2/T3 (intermediate-thickness) melanoma patients, where the greatest agreement exists. METHODS: T2/T3 and metastasis 0 melanoma cases were identified from 2004 to 2018 Surveillance, Epidemiology, and End Results data. Analysis used Cochran-Armitage test for trends, multivariable logistic regression, and Kaplan-Meier survival estimates. RESULTS: Of 66,319 eligible T2/T3 patients, 57,211 were clinically node negative; 2,191 were clinically node positive; 6,197 were clinical node unreported; and 19,044/66,319 (28.8%) had no lymph node surgery. Among clinically node-negative patients, 36,433 (63.7%) underwent sentinel lymph node biopsy and 31,026 (85.2%) were pathologically node negative; 1,499 clinically node-positive patients (68.4%) had a lymph node dissection. Lymph node dissection rates declined from 2004 to 2018, 79.8% to 32.0% for clinically node-negative/pathologically node-positive patients and 80.4% to 61.2% for clinically node-positive/pathologically node-positive patients (both P < .0001). For clinically node-negative patients, lymph node surgery compliance improved from 63.7% (2004) to 70.4% (2018) (P < .0001). Compliance correlated with younger age, male sex, tumor mitotic rate, and site (extremity > trunk/head/neck) in multivariable analysis and improved 5-year cancer-specific survival (90.0% vs 83.4%) (all P < .0001). CONCLUSIONS: Despite clear guidelines, one-third of intermediate-thickness melanoma patients in a recent cohort did not have recommended lymph node surgery. Lymph node status is a key determinant of the relative benefit of adjuvant systemic therapy and the need for active surveillance of pathologically node-positive/clinically node-negative patients. These data highlighted a clinical care gap. Efforts to improve guideline compliance are a logical strategy to improve cancer outcomes for intermediate-thickness melanoma patients.

Lymph Node Positivity of Axillary Reverse Mapping Lymph Nodes at the Time of Axillary Lymph Node Dissection: Two-Site Prospective Trial.

BACKGROUND: Axillary reverse mapping (ARM) was introduced in 2007 to identify and selectively preserve upper-extremity lymphatics during axillary lymph node surgery to decrease the risk of lymphedema. The patient population in which an ARM lymph node (LN) can be preserved during an axillary lymph node dissection (ALND) has not been established to date. This study aimed to determine the frequency of metastatic involvement of an ARM LN among patients undergoing ALND. METHODS: Patients undergoing ALND with or without immediate lymphatic reconstruction (ILR) were enrolled in a prospective trial at two institutional sites between April 2018 and Decemeber 2022. This report analyzes the ARM node positivity and total LN positivity rates during ALND for the cohort of patients enrolled in the ILR intervention arm of the study. RESULTS: The inclusion criteria were met by 139 patients, who made up the study population (133 with breast cancer and 6 with other disease). Of the breast cancer patients, 99.2% were female, 35.3% (47/133) were cT3 or greater, and 96.2% (128/133) had cN1 or greater disease. For 55 of the 133 patients (41.4%), the ARM nodes were marked and specified in the pathology report. Of the 55 patients, 39 (70.9%) had a positive LN at ALND. Of these 55 patients, 11 (20%) had positive ARM nodes. The ARM LN was the only positive node in 3 of the 11 patients. CONCLUSION: In the contemporary patient population undergoing ALND, the positivity rate of the ARM LN was relatively high, suggesting that leaving ARM LNs in patients undergoing ALND may not be oncologically safe.

Changes in Surgical Management of the Axilla Over 11 Years - Report on More Than 1500 Breast Cancer Patients Treated with Neoadjuvant Chemotherapy on the Prospective I-SPY2 Trial.

BACKGROUND: Axillary surgery after neoadjuvant chemotherapy (NAC) is becoming less extensive. We evaluated the evolution of axillary surgery after NAC on the multi-institutional I-SPY2 prospective trial. METHODS: We examined annual rates of sentinel lymph node (SLN) surgery with resection of clipped node, if present), axillary lymph node dissection (ALND), and SLN and ALND in patients enrolled in I-SPY2 from January 1, 2011 to December 31, 2021 by clinical N status at diagnosis and pathologic N status at surgery. Cochran-Armitage trend tests were calculated to evaluate patterns over time. RESULTS: Of 1578 patients, 973 patients (61.7%) had SLN-only, 136 (8.6%) had SLN and ALND, and 469 (29.7%) had ALND-only. In the cN0 group, ALND-only decreased from 20% in 2011 to 6.25% in 2021 (p = 0.0078) and SLN-only increased from 70.0% to 87.5% (p = 0.0020). This was even more striking in patients with clinically node-positive (cN+) disease at diagnosis, where ALND-only decreased from 70.7% to 29.4% (p < 0.0001) and SLN-only significantly increased from 14.6% to 56.5% (p < 0.0001). This change was significant across subtypes (HR-/HER2-, HR+/HER2-, and HER2+). Among pathologically node-positive (pN+) patients after NAC (n = 525) ALND-only decreased from 69.0% to 39.2% (p < 0.0001) and SLN-only increased from 6.9% to 39.2% (p < 0.0001). CONCLUSIONS: Use of ALND after NAC has significantly decreased over the past decade. This is most pronounced in cN+ disease at diagnosis with an increase in the use of SLN surgery after NAC. Additionally, in pN+ disease after NAC, there has been a decrease in use of completion ALND, a practice pattern change that precedes results from clinical trials.

Using US Twinkling Artifact to Identify Breast Biopsy Markers: Brief Report.

Breast biopsy markers play an essential role in the surgical management of patients with clinically node-positive breast cancer. Marking a pathology-proven lymph node ensures accurate imaging assessment of response to neoadjuvant systemic therapy and decreased false-negative rates in sentinel lymph node biopsy. There is a clinically unmet need to make breast biopsy markers, particularly in the axilla, more sonographically visible or identifiable for preoperative localization purposes. Previously described color Doppler US twinkling artifact of some breast biopsy markers in in vitro gel phantoms and in ex vivo cadaveric breasts suggests that twinkling of such markers can be leveraged for improved in vivo detection. In this retrospective case series of eight female patients (mean age, 58.6 years ± 12.3 [SD]), conventional B-mode US imaging failed to identify the biopsy marker associated with a surgical target in the breast or in an axillary lymph node. However, in each patient, the marker was successfully identified with the help of color Doppler US twinkling. Keywords: Breast, Ultrasound, Color Doppler US, Lymphatic, Artifacts, Biopsy Marker Published under a CC BY 4.0 license.

Breast Conservation Surgery and Mastectomy Have Similar Locoregional Recurrence After Neoadjuvant Chemotherapy: Results From 1462 Patients on the Prospective, Randomized I-SPY2 Trial.

Neoadjuvant chemotherapy (NAC) increases rates of successful breast-conserving surgery (BCS) in patients with breast cancer. However, some studies suggest that BCS after NAC may confer an increased risk of locoregional recurrence (LRR). We assessed LRR rates and locoregional recurrence-free survival (LRFS) in patients enrolled on I-SPY2 (NCT01042379), a prospective NAC trial for patients with clinical stage II to III, molecularly high-risk breast cancer. Cox proportional hazards models were used to evaluate associations between surgical procedure (BCS vs mastectomy) and LRFS adjusted for age, tumor receptor subtype, clinical T category, clinical nodal status, and residual cancer burden (RCB). In 1462 patients, surgical procedure was not associated with LRR or LRFS on either univariate or multivariate analysis. The unadjusted incidence of LRR was 5.4% after BCS and 7.0% after mastectomy, at a median follow-up time of 3.5 years. The strongest predictor of LRR was RCB class, with each increasing RCB class having a significantly higher hazard ratio for LRR compared with RCB 0 on multivariate analysis. Triple-negative receptor subtype was also associated with an increased risk of LRR (hazard ratio: 2.91, 95% CI: 1.8-4.6, P < 0.0001), regardless of the type of operation. In this large multi-institutional prospective trial of patients completing NAC, we found no increased risk of LRR or differences in LRFS after BCS compared with mastectomy. Tumor receptor subtype and extent of residual disease after NAC were significantly associated with recurrence. These data demonstrate that BCS can be an excellent surgical option after NAC for appropriately selected patients.

Long-term outcomes of intraoperatively-placed applicator brachytherapy for rapid completion of breast conserving treatment: An analysis of a prospective registry data.

Background and purpose: To evaluate the long-term outcome of accelerated partial breast irradiation utilizing intraoperatively placed applicator-based brachytherapy (ABB) in early-stage breast cancer. Materials and methods: From our prospective registry, 223 patients with pTis-T2, pN0/pN1mic breast cancer were treated with ABB. The median treatment duration including surgery and ABB was 7 days. The prescribed doses were 32 Gy/8 fx BID (n = 25), 34 Gy/10 fx BID (n = 99), and 21 Gy/3 fx QD (n = 99). Endocrine therapy (ET) adherence was defined as completion of planned ET or ≥ 80% of the follow-up (FU) period. Cumulative incidence of ipsilateral breast tumor recurrence (IBTR) was estimated and influencing factors for IBTR-free survival rate (IBTRFS) were analyzed. Results: 218/223 patients had hormone receptor-positive tumors, including 38 (17.0%) with Tis and 185 (83.0%) with invasive cancer. After a median FU of 63 months, 19 (8.5%) patients had recurrence [17 (7.6%) with an IBTR]. Rates of 5-year IBTRFS and DFS were 92.2% and 91.1%, respectively. The 5-year IBTRFS rates were significantly higher for post-menopausal women (93.6% vs. 66.4%, p = 0.04), BMI < 30 kg/m2 (97.4% vs. 88.1%, p = 0.02), and ET-adherence (97.5% vs. 88.6%, p = 0.02). IBTRFS did not differ with dose regimens. Conclusions: Postmenopausal status, BMI < 30 kg/m2, and ET- adherence predicted favorable IBTRFS. Our results highlight the importance of careful patient selection for ABB and encouragement of ET compliance.

Factors Associated With Ultrasound Color Doppler Twinkling by Breast Biopsy Markers: In Vitro and Ex Vivo Evaluation of 35 Commercially Available Markers.

BACKGROUND. Targeted axillary lymph node dissection after neoadjuvant systemic therapy (NST) for breast cancer depends on identifying marked metastatic lymph nodes. However, ultrasound visualization of biopsy markers is challenging. OBJECTIVE. The purpose of our study was to identify biopsy markers that show actionable twinkling in cadaveric breast and to assess the association of actionable twinkling with markers' surface roughness. METHODS. Commercial breast biopsy markers were evaluated for twinkling artifact in various experimental conditions relating to scanning medium (solid gel phantom, ultrasound coupling gel, cadaveric breast), transducer (ML6-15, 9L, C1-6), and embedding material (present vs absent). Markers were assigned twinkling scores from 0 (confident in no twinkling) to 4 (confident in exuberant twinkling); a score of 3 or greater represented actionable twinkling (sufficient confidence to rely solely on twinkling for target localization). Markers were hierarchically advanced to evaluation with increasingly complex media if showing at least minimal twinkling for a given medium. A 3D coherence optical profiler measured marker surface roughness. Mixed-effects proportional odds regression models assessed associations between twinkling scores and transducer and embedding material; Wilcoxon rank sum test evaluated associations between actionable twinkling and surface roughness. RESULTS. Thirty-five markers (21 with embedding material) were evaluated. Ten markers without embedding material advanced to evaluation in cadaveric breast. Higher twinkling scores were associated with presence of embedding material (odds ratio [OR] = 5.05 in solid gel phantom, 9.84 in coupling gel) and transducer (using the C1-6 transducer as reference; 9L transducer: OR = 0.36, 0.83, and 0.04 in solid gel phantom, ultrasound coupling gel, and cadaveric breast; ML6-15 transducer: OR = 0.07, 0.18, and 0.00 respectively; post hoc p between 9L and ML6-15: p < .001, p = .02, and p = .04). In cadaveric breast, three markers (Cork, Professional Q, MRI [Flex]) exhibited actionable twinkling for two or more transducers; surface roughness was significantly higher for markers with than without actionable twinkling for C1-6 (median values: 0.97 vs 0.35, p = .02) and 9L (1.75 vs 0.36; p = .002) transducers. CONCLUSION. Certain breast biopsy markers exhibited actionable twinkling in cadaveric breast. Twinkling was observed with greater confidence for the C1-6 and 9L transducers than the ML6-15 transducer. Actionable twinkling was associated with higher marker surface roughness. CLINICAL IMPACT. Use of twinkling for marker detection could impact preoperative or intraoperative localization after NST.

Overuse of Axillary Surgery in Patients with Ductal Carcinoma In Situ: Opportunity for De-escalation.

BACKGROUND: Ductal carcinoma in situ (DCIS) is noninvasive breast cancer and therefore nodal staging is not routinely recommended. We evaluated the use of and factors associated with axillary surgery in DCIS in the National Cancer Database (NCDB). METHODS: DCIS cases were identified from the NCDB 2012-2018. Use of axillary surgery was evaluated over time, and factors associated with axillary surgery were assessed for breast-conserving surgery (BCS) and mastectomy groups. RESULTS: We identified 178,762 patients, median age of 60 years. Majority of DCIS (87%) was ER-positive, and 14% low, 43% intermediate, and 44% high grade. Median DCIS size was 1.1 cm. BCS was performed in 72%, whereas 28% had mastectomy. Overall axillary surgery was performed in 38% and was higher in patients undergoing mastectomy compared with patients undergoing BCS (88% vs. 19%, p < 0.001). At axillary surgery, the vast majority (92%) had 1-5 nodes examined, whereas 8% had >5 nodes examined. Over time, axillary surgery decreased in BCS patients (21% in 2012 to 17% in 2018, p < 0.001) but increased slightly in mastectomy patients (86% in 2012 to 90% in 2018, p < 0.001). On multivariable analysis, factors significantly associated with axillary surgery were younger patient age, larger tumor size, higher grade, and ER-negative status. CONCLUSIONS: Factors associated with axillary surgery reflect higher risk disease for upstage to invasive cancer, indicating surgeon judgment. However, despite axillary surgery being overtreatment of DCIS, it is common in mastectomy and is performed for one in five patients undergoing BCS. This provides opportunity for improvement in breast cancer care delivery.

Surgeon Assessment of the Technical Impact of Neoadjuvant Systemic Therapy on Operable Stage III Melanoma.

INTRODUCTION: The effect of neoadjuvant systemic therapies (NST) on technical aspects of operation for resectable stage III melanoma is unknown. Prospective capture of the estimated and actual degree of difficulty of therapeutic lymphadenectomy at presentation and after NST may inform the relative merits of NST versus surgery followed by adjuvant therapy. METHODS: We designed surgeon survey tools to capture key impressions at baseline prior to NST and postoperatively. We conducted a sub-study within a multi-institutional clinical trial for high-risk operable stage III melanoma (NeoACTIVATE, NCT03554083) which enrolls clinically node-positive patients to 12 weeks of combinatorial NST determined by BRAF status. Survey data were analyzed. RESULTS: Surveys were completed for 24 of 25 patients (96%). Affected nodal basins were cervical (3, 13%) axillary (9, 38%), inguinal ± pelvic (14, 58%); 2 (8%) involved ≥ 2 basins. Baseline estimates included largest affected node size (median/range 4/1.4-11 cm), number of involved nodes (median/range 3/1-10) and tumor fixation (present in 12, 50%). At operation, actual degree of difficulty increased from the baseline estimate in 4 (17%) and decreased in 6 (25%). Surgery was less difficult, average, or more difficult versus usual operation in 4, 9, and 11 cases (17%, 38%, 46%), respectively. CONCLUSIONS: Although many operations were judged to be more difficult than the usual therapeutic lymphadenectomy, operation following NST was more often perceived as easier than more difficult versus baseline impression. Engaging surgical oncologists to perform similar structured assessments across clinical trials will permit cross-study analysis of the effect of NSTs on the technical conduct of lymphadenectomy.

Locoregional Management of the Axilla in Mastectomy Patients with One or Two Positive Sentinel Nodes: The Role of Intraoperative Pathology.

INTRODUCTION: Controversy exists regarding optimal management of the axilla in clinically node-negative (cN0) mastectomy patients with one or two positive sentinel lymph nodes (+SLNs). We evaluated the influence of frozen-section pathology on axillary management and recurrence. PATIENTS AND METHODS: We studied cN0 breast cancer patients treated from 2008 to 2018 with mastectomy and SLN surgery with one or two +SLNs. Patients with one or two +SLNs identified on frozen-section intraoperatively (FS+SLN) were compared to those with one or two +SLNs not detected by frozen section (FS-SLN). Recurrence rates were estimated using the Kaplan-Meier method. RESULTS: Of 2295 cN0 mastectomy patients, 338 patients had one or two +SLNs: 108 (32%) FS-SLN and 230 (68%) FS+SLN. In the FS+SLN cases, completion axillary lymph node dissection (cALND) was more frequent (97% vs. 39%; P < .001), and median SLN metastasis size (5 vs. 1.3 mm; P < .001) and likelihood of positive non-SLNs (31% vs. 14%; P = .02) were greater compared with FS-SLN cases. Across all 338 patients, 40% had SLN surgery alone, and 47% of cALND patients received post-mastectomy radiation therapy (PMRT). At a median follow-up of 61 months, no axillary recurrences were observed among FS-SLN patients. Among FS+SLN patients, 97% proceeded to cALND but 49% avoided PMRT; three regional nodal recurrences were observed (all in patients treated with cALND, of whom two received PMRT). CONCLUSION: Mastectomy patients with one or two FS+SLNs have a higher nodal disease burden than FS-SLN patients. The majority of FS+SLN patients underwent cALND, and 51% received PMRT with very low 5-year regional nodal recurrence rates. A substantial proportion of FS-SLN patients successfully avoided both cALND and PMRT. Frozen-section pathology analysis can guide de-escalation of axillary management.