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Background: Multi-parameter tumor gene expression assays (MPAs) are used to estimate individual patient risk and guide chemotherapy use in hormone-sensitive, HER2-negative early breast cancer. The TAILORx trial supports MPA use in a node-negative population. Evidence for MPA use in postmenopausal node-positive breast cancer has been provided by the RxPONDER trial interim analysis but this relies on the absence of superiority in an analysis where >50% of events were unrelated to breast cancer. There is much uncertainty about MPA use for premenopausal patients. OPTIMA (Optimal Personalised Treatment of early breast cancer usIng Multi-parameter Analysis) (ISRCTN42400492) is a prospective international randomized controlled trial designed to validate MPAs as predictors of chemotherapy sensitivity in a largely node-positive breast cancer population. Methods: OPTIMA is a partially blinded study with an adaptive two-stage design. The trial recruits women and men age 40 or older with resected ER-positive, HER2-negative invasive breast cancer and up to 9 involved axillary lymph nodes. Randomization is to standard management (chemotherapy and endocrine therapy) or to MPA-directed treatment using the Prosigna (PAM50) test. Those with a Prosigna tumor Score (ROR_PT) >60 receive standard management whilst those with a low score (≤60) tumor are treated with endocrine therapy alone. Endocrine therapy for pre-menopausal women includes ovarian suppression for all participants unless they experience a chemotherapy-induced menopause. Adjuvant abemaciclib is permitted. The trial will be analyzed for (1) non-inferiority of recurrence according to randomization and (2) cost-effectiveness. The key secondary outcome is non-inferiority of recurrence for patients with low ROR_PT score tumors. The efficacy analyses will be performed Per Protocol using Invasive Breast Cancer Free Survival (IBCFS) as the primary outcome measure to limit the risk of a false non-inferiority conclusion. Recruitment of 4500 patients over 8 years will permit demonstration of up to 3% non-inferiority of test-directed treatment with at least 83% power, assuming 5-year IBCFS is 87% with standard management. An integrated qualitative recruitment study addresses challenges to consent and recruitment, building on experience from the feasibility study which found that a multidisciplinary approach is important for recruitment success. OPTIMA is strongly supported by a patient group which has helped design all patient documents and which is represented on the TMG. Results: The OPTIMA main trial opened in January 2017 and has continued to recruit throughout the COVID-19 pandemic. Overall recruitment as of 1 July 2022 was 2814 (2593 from UK, 221 from Norway). Patient characteristics are well balanced between the trial arms. Currently 95% of randomized participants are eligible for inclusion in the PP analysis. 66% of the MPA-directed arm participants have been allocated to endocrine therapy only. The test failure rate is < 1%. Conclusion: OPTIMA will provide robust unbiased evidence on test-directed chemotherapy safety for both postmenopausal and premenopausal women with 1-3 involved nodes as well as for patients with 4-9 involved nodes and for patients treated with abemaciclib. Funding: OPTIMA is funded by the UK NIHR HTA Programme (10/34/501) and in Norway by KLINBEFORSK and the Norwegian Cancer Society. Views expressed are those of the authors and not those of the HTA Programme, NIHR, NHS or the Department of Health. Trial Inquiries: OPTIMA@warwick.ac.uk Patient characteristics Citation Format: Robert Stein, Andreas Makris, Iain Macpherson, Luke Hughes-Davies, Andrea Marshall, Georgina Dotchin, David A. Cameron, Belinda E. Kiely, Caroline Wilson, Anne Armstrong, Helena M. Earl, Christopher J. Poole, Janice Tsang, Bjørn Naume, Daniel Rea, Hege Ohnstad, Peter S. Hall, Stuart A. McIntosh, Bethany Shinkins, Christopher McCabe, Adrienne Morgan, John MS Bartlett, Janet A. Dunn. OPTIMA, a prospective randomized trial to validate the clinical utility and cost-effectiveness of gene expression test-directed chemotherapy decisions in high clinical risk early breast cancer. [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 OT3-32-01.

Background: Mammographic screening programmes reduce breast cancer mortality, but detect many small tumours with favourable biological features which may not progress during a woman’s lifetime. Screen-detected cancers are treated with standard surgery and adjuvant therapies, with associated morbidities. There is a need to reduce overtreatment of good prognosis tumours and numerous studies have evaluated the omission of radiotherapy in this context. However, there is little evidence to support surgical de-escalation, although percutaneous minimally invasive treatment approaches have been described. Vacuum-assisted excision (VAE) is in widespread use for management of benign lesions and lesions of uncertain malignant potential. SMALL (ISRCTN 12240119) is designed to determine the feasibility of using this approach for treatment of small invasive tumours detected within the UK NHS Breast Screening Programme (BSP). Methods: SMALL is a phase III multicentre randomised trial comparing standard surgery with VAE for screen-detected good prognosis cancers. The main eligibility criteria are age ≥47 years, unifocal grade 1 tumours with maximum diameter 15mm, which are strongly ER/PR+ve and HER2-ve, with negative clinical/radiological axillary staging. Patients are randomised 2:1 in favour of VAE or surgery; with no axillary surgery in the VAE arm. Completeness of excision is assessed radiologically, and if excision is incomplete, patients undergo open surgery. Adjuvant radiotherapy and endocrine therapy are mandated in the VAE arm but may be omitted following surgery. Co-primary end-points are: 1. Non-inferiority comparison of the requirement for a second procedure following excision 2. Single arm analysis of local recurrence (LR) at 5 years following VAE Recruitment of 800 patients will permit demonstration of 10% non-inferiority of VAE for requirement of a second procedure. This ensures sufficient patients for single arm analysis of LR rates, where expected LR free survival is 99% at 5 years, with an undesirable survival probability after VAE of 97%. To ensure that the trial as a whole only has 5% alpha, the significance level for each co-primary outcome is set at 2.5% with 90% power. The Data Monitoring Committee will monitor LR events to ensure these do not exceed 3% per year. Secondary outcome measures include time to ipsilateral recurrence, overall survival, complications, quality of life and health economic analysis. A novel feature of SMALL is the integration of a QuinteT Recruitment Intervention (QRI), which aims to optimise recruitment to the study. Recruitment challenges are identified by analysing recruiter/patient interviews and audio-recordings of trial discussions, and by review of trial screening logs, eligibility and recruitment data and study documentation. Solutions to address these are developed collaboratively, including individual/group recruiter feedback and recruitment tips documents. Results: SMALL opened in December 2019, but recruitment halted in 2020 for 5 months due to COVID-19. At 7st July 2022, 142 patients had been randomised from 26 centres, with a randomisation rate of approximately 45%, and a per site recruitment rate of 0.4-0.5 patients/month, approaching the feasibility recruitment target of 144 patients. Drawing from preliminary QRI findings and insights from patient representatives, a recruitment tips document has been circulated (on providing balanced information about treatments, encouraging recruiters to engage with patient preferences, and explaining randomisation). Individual recruiter feedback has commenced, with wider feedback delivered across sites via recruitment training workshops. Conclusion: Despite pandemic-related challenges, SMALL has an excellent recruitment rate to date and is expected to have a global impact on treatment of breast cancer within mammographic screening programmes. SMALL is funded by the UK NIHR HTA programme, award 17/42/32 Citation Format: Stuart A. McIntosh, Charlotte E. Coles, David Dodwell, Kenneth Elder, Jessica Foster, Claire Gaunt, Amanda Kirkham, Iain Lyburn, Jenna Morgan, Sangeetha Paramasivan, Sarah E. Pinder, Sarah Pirrie, Shelley Potter, Tracy Roberts, Nisha Sharma, Hilary Stobart, Elizabeth Southgate, Sian Taylor-Phillips, Matthew Wallis, Daniel Rea. SMALL: Open Surgery versus Minimally invasive vacuum-Assisted excision for smaLL screen-detected breast cancer – a UK phase III randomised multi-centre trial [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 OT3-20-02.

PURPOSE: There is currently no standardised definition for patients at high risk of recurrence of HER2-negative early breast cancer (eBC, stages 1–3) after surgery. Recognising that the assessment of high risk is often multifactorial, the aim of this modified Delphi panel was to establish expert UK consensus on this definition, separately considering HR-positive and triple-negative (TN) patients. METHODS: A total of 45 UK-based clinicians, including breast cancer oncologists and surgeons, were invited to participate. The number of respondents in each of three rounds was 29, 24 and 22 respectively. Statements were developed using the results from a targeted literature review and the guidance of a lead clinician, and comprised free-text, single-choice or numerical formats. The first round aimed to determine which factors are currently used in clinical practice to assess risk of recurrence in the populations of interest. In the subsequent rounds, the objective was to establish thresholds indicative of high risk in a 10-year timeframe for each of the factors retained in Round 1. Between each round, statements were refined, considering the distribution of responses and free-text notes provided by participants. Consensus for single-choice questions was set at a pre-defined threshold of ≥70% of respondents. RESULTS: Consensus was achieved on the need to assess age, tumour size, tumour grade, number of positive nodes, presence of inflammatory breast cancer and one or more risk prediction tools to define high risk of recurrence in all HER2-negative patients. In HR-positive patients, there was agreement on the use of one or more tumour profiling tests and biomarkers to define high risk of recurrence. However, there was no consensus on biomarker use in TN patients, and support for specific biomarkers (such as Ki-67) was conflicting for both sub-populations based on the analysis of free-text notes. Similarly, while there was consensus on the use of pCR status/residual disease to indicate high risk in TN patients, this factor failed to reach consensus for the HR-positive sub-population. Germline BRCA status and menopausal status were not considered to be key factors for risk of recurrence in either biological subtype. In the second and third rounds, thresholds indicative of high recurrence risk were agreed; it should be noted that the free-text responses provided by the participants frequently highlighted that many of the factors should be considered along a continuous scale when assessing the risk of individual patients. In HR-positive patients, these thresholds included: age < 35 years, tumour size >5 cm (each when considered independently from other risk factors); tumour grade 3 (independently or in combination with other factors); number of positive lymph nodes ≥4 when considered independently or ≥1 in combination with other factors. For patients with TN tumours, the following thresholds reached consensus, whether considered independently or in combination with other factors: tumour size >2 cm, tumour grade 3, number of positive lymph nodes ≥1. In several cases, however, no consensus could be reached on the appropriate threshold indicating high risk of recurrence. In the HR-positive sub-population, these included thresholds for age and tumour size, when considered in combination with other factors. In the TN sub-population, this included age, whether independently or in combination with other factors. CONCLUSIONS: The expert consensus reached in this panel highlights that an integrated model is important in assessing recurrence risk in eBC and that definitions of high risk differ according to biological subtype. The results may serve as a valuable reference point for clinicians to use in assessing risk of disease recurrence and in making treatment decisions after surgery in the HER2-negative eBC population. FUNDING: AstraZeneca UK Ltd. Writing support: Costello Medical. Citation Format: Ellen R. Copson, Jean E. Abraham, Jeremy P. Braybrooke, Stuart A. McIntosh, Caroline O. Michie, Carlo Palmieri, Rebecca Roylance, Saiqa Spensley. Expert consensus on the definition of high risk of recurrence in HER2-negative early breast cancer: a modified Delphi panel [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 P3-05-39.

Purpose Epidemiological studies have indicated a higher prevalence of hypothyroidism in breast cancer patients, possibly related to shared risk factors and breast cancer treatments. However, few studies have evaluated how hypothyroidism impacts survival outcomes in breast cancer patients. We aimed to determine the association between hypothyroidism and breast cancer-specific and all-cause mortality. Methods We conducted a population-based study using the Scottish Cancer Registry to identify women diagnosed with breast cancer between 2010 and 2017. A matched comparison cohort of breast cancer-free women was also identified. Using hospital diagnoses and dispensed prescriptions for levothyroxine, we identified hypothyroidism diagnosed before and after breast cancer diagnosis and determined associations with breast cancer-specific and all-cause mortality. Cox proportional hazards regression was used to calculate hazard ratios (HR) and 95% confidence intervals (CI) adjusted for potential confounders. Results A total of 33,500 breast cancer patients were identified, of which 3,802 had hypothyroidism before breast cancer diagnosis and 565 patients went on to develop hypothyroidism after. Breast cancer patients had higher rates of hypothyroidism compared with cancer-free controls (HR 1.14, 95% CI 1.01–1.30). Among breast cancer patients, we found no association between hypothyroidism (diagnosed before or after) and cancer-specific mortality (before: HR 0.99, 95% CI 0.88–1.12, after: HR 0.97, 95% CI 0.63–1.49). Similar associations were seen for all-cause mortality. Conclusion In a large contemporary breast cancer cohort, there was little evidence that hypothyroidism, either at diagnosis or diagnosed after breast cancer, was associated with cancer-specific or all-cause mortality.

Background:. Mammographic screening programmes have been shown to reduce breast cancer mortality. However, they detect many small tumours with favourable biological features which may not progress during a woman’s lifetime. These are treated with standard surgery and adjuvant therapies, which have associated morbidities. Thus, there is a need to reduce overtreatment of good prognosis tumours found by screening. Minimally invasive treatment approaches have been described but there is no prospective randomised evidence to support their routine use. Vacuum-assisted excision (VAE) is in widespread use for management of benign lesions and lesions of uncertain malignant potential. SMALL (ISRCTN 12240119) is designed to determine the feasibility of using this approach for treatment of small invasive tumours detected within the UK NHS Breast Screening Programme (BSP). Methods:. SMALL is a phase III multicentre randomised trial comparing standard surgery with VAE for screen-detected good prognosis breast cancers. The main eligibility criteria are age ≥47 years, screen-detected unifocal grade 1 tumours with maximum diameter 15mm, which are strongly ER/PR+ve and HER2-ve, with negative clinical/radiological axillary staging. Patients are randomised 2:1 in favour of VAE or surgery; with no axillary surgery in the VAE arm. Completeness of excision is assessed radiologically, and if excision is incomplete, patients undergo open surgery. Adjuvant radiotherapy and endocrine therapy are mandated in the VAE arm but may be omitted following surgery. Co-primary end-points are:1.Non-inferiority comparison of the requirement for a second procedure following excision2.Single arm analysis of local recurrence (LR) at 5 years following VAE. Recruitment of 800 patients over 4 years will permit demonstration of 10% non-inferiority of VAE for requirement of a second procedure. This ensures sufficient patients for single arm analysis of LR rates, where expected LR free survival is 99% at 5 years, with an undesirable survival probability after VAE of 97%. To ensure that the trial as a whole only has 5% alpha, the significance level for each co-primary outcome is set at 2.5% with 90% power. The Data Monitoring Committee will monitor LR events to ensure these do not exceed 3% per year. Secondary outcome measures include time to ipsilateral recurrence, overall survival, complications, quality of life and health economic analysis. A QuinteT Recruitment Intervention (QRI) is integrated throughout SMALL to optimise recruitment and informed consent. Recruitment challenges are identified by analysing recruiter/patient interviews and audio-recordings of trial discussions, and by review of screening, eligibility and recruitment data and study documentation. Solutions to address these are developed collaboratively, including individual/group recruiter feedback and recruitment tips documents. Results:. SMALL opened in December 2019, but recruitment halted in 2020 due to suspension of the NHS BSP for 5 months due to COVID-19. As of 1st July 2021, 55 patients had been approached in 10 centres, with 33 patients randomised (randomisation rate 60%). A further 23 centres are in set-up, with 8 suspended due to the pandemic. Drawing from preliminary QRI findings and insights from patient representatives, a recruitment tips document has been circulated (on introducing and discussing SMALL, providing balanced information. on treatment options and explaining randomisation). individual recruiter feedback has commenced, with wider feedback planned shortly. Conclusion:. Despite pandemic-related challenges, SMALL has an excellent recruitment rate to date and is expected to have a global impact on treatment of breast cancer within mammographic screening programmes. SMALL is funded by the UK NIHR HTA programme, award 17/42/32 Citation Format: Stuart A McIntosh, Charlotte E Coles, Carmel Conefrey, David Dodwell, Kenneth Elder, Jessica Foster, Claire Gaunt, Amanda Kirkham, Iain Lyburn, Jenna Morgan, Sangeetha Paramasivan, Sarah Pinder, Sarah Pirrie, Shelley Potter, Tracy Roberts, Nisha Sharma, Hilary Stobart, Elizabeth Southgate, Sian Taylor-Phillips, Matthew Wallis, Daniel Rea. SMALL - Open surgery versus minimally invasive vacuum-assisted excision for small screen detected breast cancer: A phase 3 randomised trial [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 OT1-06-02.

Purpose A James Lind Alliance priority setting partnership was developed to identify research priorities in breast cancer surgery from individuals with lived experience, at high genetic risk of breast cancer, and healthcare professionals (HCPs). Methods ‘Uncertainties’ were collected using an online survey. Following an evidence check and development of summary questions, an interim survey asked participants to rank their top 10 research priorities from the question list. Top-ranked questions from patient/carer, high-risk and professional groups were carried forward for discussion to a final online prioritisation workshop. Results 260 participants (101 patients/carers, 156 HCPs) submitted 940 uncertainties via the initial survey. These were analysed thematically into 128 summary questions in six topic areas. Following evidence checking, 59 questions were included in the interim survey which was completed by 572 respondents. Marked differences were seen in questions prioritised by patients/carers, HCPs and women at high-risk. The top eight priorities in patient/carer and professional groups and top two priorities for high-risk women were carried forward to the online workshop at which 22 participants discussed and agreed the final top 10. Key themes included de-escalation of breast and axillary surgery, factors impacting the development/detection of locoregional recurrence and optimal provision of support for informed treatment decision-making. Conclusion The top 10 research priorities in breast cancer surgery have been agreed. However, the observed differences in research priorities identified by patients and professional groups were not anticipated. Top priorities from both groups should inform future UK breast cancer surgical research, to ensure that it addresses questions that are important to breast cancer community as a whole.

Background SMALL (ISRCTN 12240119) is a novel UK phase III multicentre randomised trial comparing vacuum-assisted excision (VAE) to surgery for small screen-detected breast cancers with biologically favourable characteristics. Acceptance by the clinical community and recruitment to SMALL was anticipated to be challenging as it involves randomisation, surgical de-escalation and minimally-invasive percutaneous treatment (VAE). A QuinteT Recruitment Intervention (QRI) has therefore been integrated throughout SMALL’s recruitment period, with the aim of optimising recruitment and informed consent. Methods The QRI in SMALL has involved the analysis of: a) screening log data b) written views from recruiters on the two treatments and their advantages/disadvantages c) in-depth semi-structured interviews with members of the Trial Management Group (TMG) and clinician-recruiters and d) audio-recordings of recruitment discussions with potentially eligible patients. Recruitment challenges were identified and addressed through the provision of written recruitment tips documents, and group and individual feedback sessions with recruiters. Results There was widespread support for the concept of the SMALL trial within the clinical community. Recruiters recognised the pioneering role of SMALL as the only current surgical de-escalation randomised trial in screen-detected breast cancer. Key recruitment challenges revolved around i) healthcare professionals (HCPs) who met patients early in the pathway providing information indicating that they were being referred for surgery (without mentioning SMALL or VAE), ii) concerns around the balance of de-escalation/escalation of different treatment modalities (e.g. some clinicians may prefer to de-escalate radiotherapy in preference to surgery in low-risk patients), iii) challenges in articulating equipoise in a surgical de-escalation trial, iv) patient preferences (primarily for surgery) and recruiter discomfort in exploring/addressing such preferences and v) fewer eligible patients than anticipated. QRI actions to overcome these issues included developing a tips document for HCPs meeting patients early in the pathway, highlighting the need to refrain from making treatment recommendations. A more generic tips document was also developed emphasising the importance of the early introduction of the study, provision of balanced information about both treatments, encouraging recruiters to engage with patients’ concerns and preferences, and adequate explanation of randomisation. Group and individual feedback sessions focussed on two key areas – articulating equipoise through balanced information provision, and considering optimal ways to explore patient preferences where they are expressed. Despite the many set-up and recruitment challenges that arose from opening at the start of the pandemic, SMALL has recruited 142 patients to date from 23 sites, with an approached to randomised patient ratio of ~50%. Conclusion SMALL is a novel surgical de-escalation study in breast cancer, which will provide critical evidence to support reductions in treatment of good prognosis disease. Using a range of qualitative methodology, the QRI has identified both broad support for the study within the clinical community, but has also identified barriers to recruitment at both clinician and patient level. These challenges have been addressed employing a range of methods, and the recruitment level and approach/randomised ratio shows the overall acceptability of this study to patients. Further work will involve interviews with patients, with a focus on their views on de-escalation, and further recruiter feedback sessions. Taken together, theis data will help inform the development and design of future de-escalation and treatment optimisation studies in breast cancer. SMALL is funded by the UK NIHR HTA programme, award 17/42/32 Citation Format: Stuart A. McIntosh, Charlotte E. Coles, David Dodwell, Kenneth Elder, Jessica Foster, Claire Gaunt, Amanda Kirkham, Iain Lyburn, Jenna Morgan, Sarah E. Pinder, Sarah Pirrie, Shelley Potter, Tracy Roberts, Nisha Sharma, Hilary Stobart, Elizabeth Southgate, Sian Taylor-Phillips, Matthew Wallis, Daniel Rea, Sangeetha Paramasivan. Recruitment challenges in a UK surgical de-escalation study: preliminary qualitative research findings from the SMALL trial [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 P6-05-17.

Introduction\ud \ud Evidence based guidelines for the optimal management of breast cancer locoregional recurrence (LRR) are limited, with potential for variation in clinical practice. This national practice questionnaire (NPQ) was designed to establish the current practice of UK breast multidisciplinary teams (MDTs) regarding LRR management.\ud \ud \ud \ud Methods\ud \ud UK breast units were invited to take part in the MARECA study MDT NPQ. Scenario-based questions were used to elicit preference in pre-operative staging investigations, surgical management, and adjuvant therapy.\ud \ud \ud \ud Results\ud \ud 822 MDT members across 42 breast units (out of 144; 29%) participated in the NPQ (February–August 2021). Most units (95%) routinely performed staging CT scan, but bone scan was selectively performed (31%).\ud \ud \ud \ud For patients previously treated with breast conserving surgery (BCS) and radiotherapy, few units (7%) always/usually offered repeat BCS. However, in the absence of radiotherapy, most units (90%) always/usually offered repeat BCS. For patients presenting with isolated local recurrence following previous BCS and SLNB (sentinel lymph node biopsy), most units (95%) advocated repeat SLNB. Where SLNs could not be identified, 86% proceeded to a four-node axillary sampling procedure.\ud \ud \ud \ud For ER positive, HER2 negative, node negative local recurrence, 10% of units always/usually offered chemotherapy. For ER positive, HER2 negative, node positive local recurrence, this recommendation increased to 64%. For triple negative breast cancer local recurrence, 90% of units always/usually offered chemotherapy.\ud \ud \ud \ud Conclusion\ud \ud This survey has highlighted where consistencies and variations exist in the multidisciplinary management of breast cancer LRR. However, further research is required to determine how these management patterns influence patient outcomes, which will further refine optimal treatment pathways.

© 2018 Elsevier Ltd The 2013 Breast Cancer Campaign gap analysis established breast cancer research priorities without a specific focus on surgical research or the role of surgeons on breast cancer research. This Review aims to identify opportunities and priorities for research in breast surgery to complement the 2013 gap analysis. To identify these goals, research-active breast surgeons met and identified areas for breast surgery research that mapped to the patient pathway. Areas included diagnosis, neoadjuvant treatment, surgery, adjuvant therapy, and attention to special groups (eg, those receiving risk-reducing surgery). Section leads were identified based on research interests, with invited input from experts in specific areas, supported by consultation with members of the Association of Breast Surgery and Independent Cancer Patients' Voice groups. The document was iteratively modified until participants were satisfied that key priorities for surgical research were clear. Key research gaps included issues surrounding overdiagnosis and treatment; optimising treatment options and their selection for neoadjuvant therapies and subsequent surgery; reducing rates of re-operations for breast-conserving surgery; generating evidence for clinical effectiveness and cost-effectiveness of breast reconstruction, and mechanisms for assessing novel interventions; establishing optimal axillary management, especially post-neoadjuvant treatment; and defining and standardising indications for risk-reducing surgery. We propose strategies for resolving these knowledge gaps. Surgeons are ideally placed for a central role in breast cancer research and should foster a culture of engagement and participation in research to benefit patients and health-care systems. Development of infrastructure and surgical research capacity, together with appropriate allocation of research funding, is needed to successfully address the key clinical and translational research gaps that are highlighted in this Review within the next two decades.