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Introduction: Axillary lymph node dissection (ALND) has always been part of breast cancer (BC) treatment. However, during the past 25 years, the surgical management of the axilla has shifted towards a more conservative approach. Until now, ALND has remained the standard surgical technique when the sentinel lymph node (SLN) is macrometastatic. However, ALND may now be considered overtreatment for early-stage BC. The SINODAR-ONE trial is a prospective non-inferiority multicenter randomized study aimed at assessing the role of ALND in patients undergoing either breast-conserving surgery (BCS) or mastectomy for T1-2 BC presenting 1-2 macrometastatic SLNs. Objectives: The primary endpoint was to evaluate whether sentinel lymph node biopsy (SLNB) only was associated with clinically relevant worsening of the prognosis compared with ALND in terms of overall survival (OS). The secondary endpoint was to evaluate whether there was increased regional (lymph node recurrence) or distant recurrence in terms of recurrence-free survival (RFS) in patients with macrometastatic SLN who did not undergo ALND. Methods: Patients were randomly assigned (1:1 ratio) to either removal of ≥10 axillary level I/II non-SLNs followed by adjuvant therapy (standard arm) or no further axillary treatment (experimental arm). Results: The trial started in April 2015 and ceased in April 2020, involving 889 patients. The majority of the patients (75.2%) underwent BCS; 328 of 439 patients (74.7%) in the standard treatment arm, and 333 of 440 patients (75.7%) in the experimental treatment arm. 218 patients (24.8%) underwent mastectomy. SLN status at randomization was comparable between the two groups of treatment, with a median number of two SLNs removed and a median number of one positive SLN in both arms. The median number of non-SLNs identified at definitive histopathological evaluation was 16 (interquartile range [IQR] 12–21) in the ALND group. Overall, 193 of 439 patients (44.0%) in the standard treatment arm had additional macrometastases in the removed axillary lymph nodes. However, the median number of positive non SLNs was 0 (IQR 0–1) in the ALND group. Median follow-up was 34.0 months. There were eight deaths (ALND, 4; SNLB only, 4), with a 5-year cumulative mortality of 5.8% and 2.1% in the standard and experimental arm, respectively (p = 0.984). There were 26 recurrences (ALND 11; SNLB only, 15), with a 5-year cumulative incidence of recurrence of 6.9% and 3.3% in the standard and experimental arm, respectively (p = 0.444). Only one axillary lymph node recurrence was observed in each arm. The 5-year OS rates were 98.9% and 98.8%, in the ALND and SNLB only arm, respectively (p = 0.936). Conclusion: The 3-year survival and relapse rates of T1-2 BC patients with 1-2 macrometastatic SLNs treated with SLNB only, and adjuvant therapy, were not inferior to those of patients treated with ALND. These results do not support the use of routine ALND in patients undergoing BCS. However, given the low number of patients treated with mastectomy, there is no certainty that ALND omission can be extended also to this sub-group. In order to collect further evidence regarding the safety of the experimental treatment in patients candidates for mastectomy, the reopening of the enrollment of these patients as part of a single-arm experimental study started in June 2022. Citation Format: Damiano Gentile, Wolfgang Gatzemeier, Andrea Sagona, Erika Barbieri, Alberto Testori, Valentina Errico, Alberto Bottini, Simone Di Maria Grimaldi, Giulia Caraceni, Luca Boni, Paolo Bruzzi, Bethania Fernandes, Davide Franceschini, Ruggero Spoto, Rosalba Torrisi, Marta Scorsetti, Armando Santoro, Giuseppe Canavese, Corrado Tinterri. Preservation of axillary lymph nodes in breast cancer patients undergoing mastectomy with 1-2 metastatic sentinel lymph nodes: The current status and future perspectives of the multicenter randomized clinical trial SINODAR-ONE [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-06-01.

Introduction: Patients with triple-negative (TN) or HER2-enriched ipsilateral breast cancer recurrence (IBCR) seem to be excluded from a second breast-conserving surgery (BCS) under the assumption that salvage mastectomy would provide better oncological outcomes. Objectives: The objective of this study was to describe the clinical features of these patients, to compare the two surgical alternatives (salvage mastectomy versus second BCS) in terms of oncological results, and to identify independent factors influencing prognosis and surgical treatment. Methods: We retrospectively reviewed all the consecutive patients with histologically confirmed TN or HER2-enriched IBCR. Disease-free survival (DFS), distant disease-free survival (DDFS), overall survival (OS), and breast cancer-specific survival (BCSS) were analyzed and compared between the two groups. Results: Eighty-five patients were affected by TN or HER2-enriched IBCR, with a median age of 60 years (range, 32-87 years). The majority of patients (72.9%) were treated with salvage mastectomy. There was no significant difference in terms of DFS between patients receiving a second BCS or mastectomy (p=0.596). However, patients undergoing a second BCS had significantly better DDFS, OS, and BCSS compared to mastectomy (p=0.009; p=0.002; p=0.001, respectively). Tumor dimension < 16 mm (78.3% versus 38.7%, hazard ratio (HR)=3.602, 95% confidence interval (95% CI)=1.534-8.459, p=0.003) was found to significantly increase the probability of receiving a second BCS and positively affects recurrence and survival outcomes (DFS: HR=8.065, 95% CI=2.320-28.034, p=0.001; DDFS: HR=17.011, 95% CI=3.853-75.099, p=0.001; OS: HR: 13.881, 95% CI=2.730-70.579, p=0.002; BCSS: HR=36.773, 95% CI=4.579-295.322, p=0.001). Second BCS represents an independent protective factor for OS and BCSS (OS: HR=0.246, 95% CI=0.027-0.697, p=0.002; BCSS: HR=0.313, 95% CI=0.092-0.511, p=0.002). Conclusion: Salvage mastectomy is not always necessary and it does not seem to increase survival compared to a second BCS. This reinforces the concept that the prognosis of TN and HER2-enriched BC recurrence is mainly driven by the biology of the disease, rather than by the extent of surgery. In patients with small (< 16 mm) aggressive subtypes of IBCR, a second conservative approach can still be evaluated and offered, presenting acceptable loco-regional control and survival. Citation Format: Damiano Gentile, Andrea Sagona, Erika Barbieri, Simone Di Maria Grimaldi, Ruggero Spoto, Davide Franceschini, Stefano Vaccari, Valeriano Vinci, Ersilia Biondi, Lorenzo Scardina, Corrado Tinterri. Salvage mastectomy is not always necessary for aggressive subtypes of ipsilateral breast cancer recurrence: A single-institution retrospective study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-09-09.

BackgroundBRCA-mutation carriers have a lifetime risk of breast cancer (BC) that ranges from 36 to 70%. For patients (pts) without mutation, breast conserving surgery (BCS) (followed by radiation therapy) is the treatment of choice since it offers similar survival to that of unilateral mastectomy. However, the optimal local management in BRCA-mutation carriers remains a matter of debate and the role of bilateral salpingo-oophorectomy (BSO) in reducing BC risk might be influenced by age and medical BC treatments (such as GnRH analogues). Patients and methodsWe retrieved clinical pathologic characteristics of 124 BRCA-mutated BC pts, consecutively tested at our Institution from 2008 to 2018. Primary end-point was recurrence-free survival (RFS) evaluation in terms of disease-free survival (DFS), distant DFS (DDFS) and overall survival (OS). Secondary end-point was identification of independent predictive factors for BCS. Clinical pathologic characteristics were evaluated and compared using univariate and multivariate analysis. Kaplan-Mayer curves were used to describe DFS, DDFS and OS. ResultsMedian age at BC surgery was 41 years (range 24-74), most of the pts (79%) were pre-menopausal and presented with ductal invasive carcinoma (91.9%). As per biological subtype, 63 (50.8%) pts had luminal-like BC, 52 (41.9%) triple negative (TN) BC and 9 (7.3%) HER2 enriched-like BC. More than half pts (62.9%) presented with G3 tumors and median Ki-67 was 40% (range 5-95). 17 (13.7%) and 80 (64.5%) pts underwent neo-adjuvant and adjuvant chemotherapy, respectively; 64 (51.6%) pts received adjuvant endocrine therapy, 39 (31.5%) with the addition of GnRH analogue. When comparing BCS to mastectomy, regardless of BSO, we could not observe any statistically significant difference in all the RFS end-points. 10-year DFS rate was 56.4% and 79.5%, respectively (p=0.187); 10-year DDFS rate was 83.7% and 82.3%, respectively (p=0.689); 10-year OS rate was 87.7% and 85.1%, respectively (p=0.947). At a multivariate analysis, age ≤41 years (p=0.008; OR 0.309; 95% CI 0.190-0.513) and primary tumor dimension ≤21 mm (p=0.008; OR 0.320; 95% CI 0.114-0.426), were the only predictors of breast surgery type (BCS compared to any other surgical treatment). ConclusionsOur data suggest that young pre-menopausal BRCA-mutated pts with small tumors may not need up-front mastectomy and BSO might be postponed, when ovarian cancer risk epidemiologically rises and potential reproductive desire is fulfilled. Citation Format: Agnese Losurdo, Damiano Gentile, Monica Zuradelli, Andrea Sagona, Erika Barbieri, Monica Barile, Paolo Bianchi, Rosalba Torrisi, Wolfgang Gatzemeier, Marta Scorsetti, Corrado Tinterri, Armando Santoro. Breast conserving surgery in BRCA-mutation carriers. A single Institution experience [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-16.

Background A small proportion of patients with primary breast cancer who receive breast conserving surgery (BCS) will develop an ipsilateral breast cancer recurrence (IBCR). In these patients, mastectomy is still considered the treatment of first choice, even if a second conservative surgical approach is technically feasible. The aims of our study are to analyze the characteristics of patients with IBCR after BCS, evaluate and compare the different treatment modalities (repeat BCS vs. mastectomy) in terms of patients and tumor characteristics, disease-free interval (DFI), disease-free survival (DFS), and overall survival (OS).MethodsOur prospectively maintained institutional database was queried, and 309 patients with IBCR after BCS who underwent either repeat BCS or mastectomy, between January 2008 and December 2018, were identified. Ipsilateral breast cancer recurrence was defined as a local tumor reappearance in the same breast or in the surgical scar. Exclusion criteria were: age Citation Format: Damiano Gentile, Andrea Sagona, Chiara Annunziata Pasqualina Anghelone, Erika Barbieri, Emilia Marrazzo, Wolfgang Gatzemeier, Giuseppe Canavese, Valentina Errico, Alberto Testori, Corrado Tinterri. Ipsilateral breast cancer recurrence: Treatment and long-term oncological results at a high volume center [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 PS1-16.

Introduction: Treatment of early-stage beast cancer (BC) has changed since recent evidence showed that neoadjuvant chemotherapy (NAC) can reduce residual tumor cellularity (RTC) and improve patient outcomes. Achieving a pathologic complete response (pCR) has been associated with significantly improved disease-free survival (DFS), distant disease-free survival (DDFS), and overall survival (OS). However, among patients treated with NAC, few experience pCR, while approximately 60-80% of them achieve a pathologic partial response (pPR). In previous studies, BC patients with different grades of pPR have been usually grouped and analyzed together, with inconsistent results and unclear prognostic significance. Objectives: The primary aims of this study were to describe the clinical and treatment characteristics of BC patients treated with NAC, to identify independent predictive factors of pCR, and to compare the oncologic outcomes between patients achieving pCR or pPR. The secondary aim of this study was to measure the RTC of BC patients with pPR and to compare the outcomes of patients with different RTC in order to improve prognostic information. Methods: All the consecutive BC patients undergoing NAC at the Breast Unit of IRCCS Humanitas Research Hospital (Milan, Italy) between October 2006 and April 2020 and their corresponding post-operative pathology slides were reviewed. The following exclusion criteria were used: excisional biopsy or debulking surgery as first BC operation, patients with a previous BC diagnosis or other prior or synchronous malignancies, male patients, unknown NAC regimen, disease progression during NAC, and follow-up ≤12 months. Results: A total of 495 BC patients received NAC. Overall, 148 (29.9%) patients achieved pCR, while 347 (70.1%) had pPR, and median RTC was 40%. At multivariable analysis, 3 independent factors predicting pCR were identified. Tumor stage pre-NAC (cT1-2 84.5% versus cT3-4 15.5%, odds ratio (OR)=0.119, 95% confidence interval (95%CI)=0.048-0.189, p=0.001), BC sub-type (HER2-enriched 54.7% versus triple-negative 29.8% versus luminal-like 15.5%, OR=2.178, 95%CI=2.055-2.301, p=0.001), and vascular invasion (absence 98.0% versus presence 2.0%, OR=0.022, 95%CI=0.004-0.090, p=0.001). Patients with BC undergoing NAC and achieving pCR presented statistically significant longer DFS, DDFS, and OS (p = < 0.001). Patients with RTC < 40% presented statistically significant better DFS and DDFS (p = 0.033, p = 0.015, respectively). However, no statistically significant difference in terms of OS was observed between RTC < 40% and RTC ≥40% groups (p = 0.148). Conclusions: Tumor stage pre-NAC, BC sub-type, and vascular invasion are significantly and independently associated with pCR. Patients with pCR present a better prognosis compared to patients with pPR in terms of DFS, DDFS, and OS. Measurement of RTC in BC patients with pPR improves the prognostic information that can be obtained from the assessment of the pathologic response. Different patterns of residual disease play an important role in predicting the risk of subsequent loco-regional and distant recurrence, and patients with RTC < 40% present significantly better DFS and DDFS. Citation Format: Damiano Gentile, Andrea Sagona, Camilla De Carlo, Bethania Fernandes, Simone Di Maria Grimaldi, Erika Barbieri, Wolfgang Gatzemeier, Lorenzo Scardina, Ersilia Biondi, Flavia Jacobs, Giulia Vatteroni, Corrado Tinterri. Evaluation of pathologic response and residual tumor cellularity following neo-adjuvant chemotherapy predict prognosis in breast cancer patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-32.

Introduction: Sentinel lymph node (SLN) staging is currently used to avoid complete axillary lymph node dissection (ALND) in breast cancer (BC) patients. The SLN is the only site of axillary metastasis (MTS) in ≥60% of cases. Recently, a randomized controlled trial (Z0011) comparing SLN biopsy (SLNB) alone with SLNB followed by ALND in patients with 1-2 SLNs+ demonstrated no significant statistical difference in relapse and overall survival (OS) rates among the two different groups. However, this study had some limitations: small tumor size (≤2cm in 70% of cases), frequent presence of only microMTS in SLN (40%), prevalent use of “whole breast” adjuvant radiotherapy (>90%). Given these considerations, the SINODAR-ONE study started in April 2015. Objectives: The aims are to assess whether ALND omission in BC patients with 1-2 SLNs+ is associated with worse survival and/or increased rate of regional/distant relapse. Thus evaluating whether SLNB is or is not inferior to ALND. Primary endpoint is OS. Secondary endpoints are disease-free survival (DFS) referring to distant MTS and loco-regional recurrence. Methods: Patients received either mastectomy or conservative surgery plus radiotherapy. They all underwent SLNB and were randomly divided into two arms of treatment: standard (SLNB plus ALND) or experimental treatment (only SLNB). According to multidisciplinary evaluation, patients could undergo additional adjuvant radiotherapy, chemo- and/or hormonal therapy, or no further therapy. Eligibility criteria: age 40-75 years; primary invasive T1-T2 tumor; axillary nodes cN0; no more than 2 macro-metastatic SLNs; no distant MTS; no neo-adjuvant therapy; no previous invasive BC. Exclusion criteria: in situ, inflammatory, contralateral BC; micro-metastatic SLNs; pregnancy or breast feeding; comorbidity impeding adjuvant therapy. All analyses were performed both on all patients according to the Intention-To-Treat principle and excluding those patients who did not receive the axillary treatment randomly assigned. Statistical analysis: OS and DFS were calculated using the Kaplan-Meier Product Limit Estimator and differences between arms were assessed with the log-rank test. Results: The enrollment of patients ended in April 2020 with a total of 889 cases (443: standard arm; 446: experimental arm). In April 2021, we conducted a preliminary analysis on 889 patients. We found the two groups homogeneous for epidemiologic characteristics (age and menopausal status), tumor characteristics (tumor size, pTNM, immunohistochemistry, histology, grading, vascular and lymphatic invasion), and adjuvant therapies. The majority of patients (77.2%) received breast conserving surgery, while 22.8% of patients underwent mastectomy. A median of 2 SLNs were removed in both arms. Overall, only 3 micro-metastatic SNLs were found (1 in the standard arm and 2 in the experimental arm). Conclusion: In sum, OS rate is 99.1% and 99.3% in the standard and experimental arm, respectively; DFS rate is 96.8% and 95.9% in the standard and experimental arm, respectively. After a median follow-up of 36 months, there has been only one axillary recurrence in the experimental arm. Additionally, we found seven distant relapses in both arms; four and three deaths in the standard and experimental arm, respectively. Citation Format: Damiano Gentile, Wolfgang Gatzemeier, Erika Barbieri, Andrea Sagona, Alberto Bottini, Valentina Errico, Alberto Testori, Marta Scorsetti, Giuseppe Canavese, Corrado Tinterri. Preservation of axillary lymph nodes compared to complete dissection in T1-T2 breast cancer patients presenting 1-2 metastatic sentinel lymph nodes. A multicenter randomized clinical trial. Sinodar One [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS4-05.

Introduction: Sentinel lymph node (SLN) staging is currently used to avoid complete axillary lymph node dissection (ALND) in breast cancer (BC) patients. The SLN is the only site of axillary metastasis (MTS) in ≤60% of cases. Recently, a randomized controlled trial (Z0011) comparing SLN biopsy (SLNB) alone with SLNB followed by ALND in patients with 1-2 SLNs+ demonstrated no significant statistical difference in relapse and overall survival rates among the two different groups. However, this study had some limitations: small tumor size (≤2cm in 70% of cases), frequent presence of only microMTS in SLN (40%), prevalent use of “whole breast” adjuvant radiotherapy (>90%). Given these considerations, the SINODAR-ONE study started in April 2015.Objectives: The aims are to assess whether ALND omission in BC patients with 1-2 SLNs+ is associated with worse survival and/or increased rate of regional/distant relapse. Thus evaluating whether SLNB is or is not inferior to ALND. Primary endpoint is overall survival (OS). Secondary endpoints are disease-free survival (DFS) referring to distant MTS and loco-regional recurrence. Methods: Patients receive either mastectomy or conservative surgery plus radiotherapy. They all undergo SLNB and are randomly divided into two arms of treatment: standard (SLNB plus ALND) or experimental treatment (only SLNB). According to multidisciplinary evaluation, patients may undergo additional adjuvant radiotherapy, chemo- and/or hormonal therapy , or no further therapy. Eligibility criteria: age 40-75 years; primary invasive T1-T2 tumor; axillary nodes clinically N0; no more than 2 macro-metastatic SLNs; no distant MTS; no neo-adjuvant therapy; no previous invasive BC; signed informed consent. Exclusion criteria: in situ, inflammatory, contralateral BC; micro-metastic SLNs; pregnancy or breast feeding; comorbidity impeding adjuvant therapy. All analyses are performed both on all patients according to the Intention-To-Treat principle and excluding those patients who did not receive the axillary treatment randomly assigned. Statistical analysis: OS and DFS are calculated using the Kaplan-Meier Product Limit Estimator and differences between arms are assessed with the log-rank test. Results: The enrollment of patients ended in April 2020 with a total of 889 cases (443: standard arm; 446: experimental arm). In June 2020, we conducted an ad interim analysis on 889 patients. We found the two groups homogeneous for epidemiologic characteristics (age and menopausal status), tumor characteristics (tumor size, pTNM, immunohistochemistry, histology, grading, vascular and lymphatic invasion), adjuvant therapies and surgery on T. In particular we have performed a 23,1% of mastectomies in the standard arm and 20,1% in the experimental arm. We found a median of 2 sentinel lymph nodes removed in both arms and 1 non-sentinel positive lymph node in the experimental arm, and only 3 micro-metastases (1 in the standard arm and 2 in the experimental arm). Conclusion: In sum, with a median follow-up of 30 months, there have been no axillary recurrence in both arms. In the standard arm we found 8 total events (2 deaths and 6 distant relapses) and in in the experimental arm 6 events (1 death and 5 distant relapses), with a projected 5-years cumulative incidence of 6,5% in standard arm and 4,85% in the experimental arm. Citation Format: Corrado Tinterri, Emilia Marrazzo, Chiara Anghelone, Erika Barbieri, Andrea Sagona, Alberto Bottini, Arianna Rubino, Damiano Gentile, Wolfgang Gatzemeier, Valentina Errico, Alberto Testori, Giuseppe Canavese. Preservation of axillary lymph nodes compared to complete dissection in T1-T2 breast cancer patients presenting 1-2 metastatic sentinel lymph nodes : A multicenter randomized clinical trial. Sinodar One. [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 PD4-01.

Introduction Sentinel lymph node (SLN) staging is currently used to avoid complete axillary lymph node dissection (ALND) in breast cancer (BC) patients with negative SLNs without jeopardizing survival or regional control. International guidelines keep recommending ALND in the presence of positive (+) SLNs. However SLN is the only site of axillary metastasis (MTS) in many cases (60%). Retrospective studies have also shown a low risk of locoregional relapse in patients with SLNs+ not receiving ALND.This latter finding was recently confirmed in a randomized trial comparing SLN biopsy (SLNB) alone with SLNB followed by ALND in patients with 1-2 SLNs+. However the observation of both similar relapse rate and survival in the 2 arms and the conclusion of a non-inferiority of SLNB compared to ALND require cautiousness because of some study limitations: premature enrollment cessation due to death rate lower than expected, short follow-up (6 years), small tumor size (≤2cm in 70% of cases), frequent presence of only microMTS in SLN (40%), prevalent use of “whole breast” adjuvant radiotherapy (>90%) which irradiates the breast but also the I° axillary level, thereby contributing to the low rate of regional relapse in the SLNB arm due to lymph node sterilization. Consequently further randomized trials with more precise selection criteria based on homogeneous clinico-pathological features and with longer follow-up are needed to confirm that performing only SLNB does not affect survival or relapse risk in patients with 1-2 SLNs+. Materials and Methods Primary and secondary aims of the present 2-arm randomized trial are to assess whether ALND omission in BC patients with 1-2 SLNs+ is associated with worse survival and/or increased rate of regional/distant relapse, respectively, thus evaluating whether SLNB is or is not inferior to ALND. Patients receive either conservative surgery or mastectomy and radiotherapy. They all undergo intraoperative SLNB and SLN evaluation, and are randomly assigned to either further dissection of level I-II axillary lymph nodes (standard ALND arm) or absence of any axillary surgery (experimental SLNB arm). According to International Guidelines post-surgery treatments. Eligibility criteria are: age 40-75 years; primary invasive T1-T2 tumor; axillary nodes clinically N0; no more than 2 SLNs presenting macroMTS at intraoperative or definitive histological evaluation; no distant MTS; no neoadjuvant therapy; no previous invasive BC, signed informed consent. Exclusion criteria are: in situ, inflammatory, contralateral BC; presence of only microMTS in the SLN+; pregnancy or breast feeding; comorbidity impeding adjuvant therapy. Follow-up controls foresee: clinical examination every 6 months for 5 years and yearly thereafter; annual mammography and breast echography; annual axillary echography for patients in the SLNB arm; additional laboratory and instrumental surveys in case of suspected onset of distant MTS. The primary endpoint is overall survival (OS). Secondary endpoints are disease-free survival (DFS) referring to distant MTS and to locoregional (ipsilateral breast or axillary, internal mammary or sopraclaveolar lymph nodes) disease recurrence. All analyses are performed both on all patients according to the Intention-To-Treat principle and excluding those patients who did not receive the axillary treatment randomly assigned. Citation Format: Corrado Tinterri, Emilia Marrazzo, Federico Frusone, Wolfgang Gatzemeier, Erika Barbieri, Andrea Sagona, Alberto Bottini, Valentina Errico, Alberto Testori, Giuseppe Canavese. Preservation of axillary lymph nodes compared to complete dissection in T1-T2 breast cancer patients presenting 1-2 metastatic sentinel lymph nodes: A multicenter randomized clinical trial. Sinodar One Study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT3-01-02.

Purpose: Studies have shown that the 70-gene signature (MammaPrint®) (MP) may outperform clinicopathological risk assessment and may predict the benefit from chemotherapy (CT) in patients (pts) with early-stage breast cancer. However, the need of fresh tissue and the high cost of the assay limit its use in daily clinical practice. We investigated whether 1) tumor clinicopathologic features can predict MP risk (high vs. low); 2) MP results could help to make decisions for the use of CT in pts with ER positive (ER+ve) breast cancer beyond recommendations of known international guidelines (NCCN, St. Gallen). Patients and methods: Women with operable invasive breast cancer without evidence of distant disease undergoing surgery at the Breast Surgery Department were enrolled into the study. A 3 mm punch biopsy of the tumor was obtained from the specimen within the first hour after surgery. Samples were shipped to the laboratory in an RNA-stabilizing solution and were studied to ensure the presence of at least 30% of tumor cells and a customized microarray containing 70 genes was analyzed as described by the manufacturer. Results: 124 consecutive pts were enrolled into the study; 106 tumor samples were adequate for the microarray. Median age was 53 yrs (range 28–83), mean tumor size was 2.3 cm (SD ±1.34), 52.4% pts had pN0, 55% of tumors had Ki-67 ≥20% and 36% were poorly differentiated. ER were detected in ≥50% of cells in 82% and As expected, poorly differentiated, ER and PgR negative, HER2 positive and highly proliferating tumors were more likely to be classified as high-MP. We then focused our analysis on ER and PgR +ve, HER2 negative tumors and assessed features correlated with MP results in this subgroup. Unexpectedly, 31/80 (39%) of these tumors were classified as high-MP vs. 49 (61%) low-MP. We found that tumor size (T1 vs. T2-T4), poor differentiation (G3 vs G1-2) and high proliferation (Ki-67 ≥20%) were significantly associated with a high-MP result. In an exploratory multivariate analysis tumor size and Ki-67 remained as independent predictors of high-MP result. At last, when we compared MP risk with recommendations for AT from international guidelines we found that in the subgroup of candidates for endocrine therapy (ET) in whom the benefit from the addition of CT is undetermined, 25/68 pts (37%) were high-MP and 43 pts (63%) low-MP. When we considered recommendations for AT proposed by our multidisciplinary team according to international guidelines, 11/25 pts (44%) with high-MP received ET only and 14 pts (56%) CT + ET, while among 43 pts with low-MP only 9 received both CT and ET. Conclusions: Our study shows that the 70-gene signature was feasible in the clinical setting, as 85% of tumor samples were adequate. A substantial proportion of ER/PgR+ve, HER2 negative tumors was classified as high-MP; within this subgroup, proliferation and tumor size independently predicted high-MP results. In 20 pts, MP risk would have resulted in discordant recommendations for AT compared to those based on standard clinicopathologic features. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-09-27.