Understanding breast cancer complexity to improve patient outcomes: The St Gallen International Consensus Conference for the Primary Therapy of Individuals with Early Breast Cancer 2023.

The 18th St Gallen International Breast Cancer Conference held in March 2023, in Vienna, Austria, assessed significant new findings for local and systemic therapies for early breast cancer with a focus on the evaluation of multimodal treatment options. The emergence of more effective, innovative agents in both the preoperative (primary or neoadjuvant) and post-operative (adjuvant) settings has underscored the pivotal role of a multidisciplinary approach in treatment decision making, particularly when selecting systemic therapy for an individual patient. The importance of multidisciplinary discussions regarding the clinical benefits of interventions was explicitly emphasized by the consensus panel as an integral part of developing an optimal treatment plan with the 'right' degree of intensity and duration. The panelists focused on controversies surrounding the management of common ductal/no special type and lobular breast cancer histology, which account for the vast majority of breast tumors. The expert opinion of the panelists was based on interpretations of available data, as well as current practices in their professional environments, personal and socioeconomic factors affecting patients, and cognizant of varying reimbursement and accessibility constraints around the world. The panelists strongly advocated patient participation in well-designed clinical studies whenever feasible. With these considerations in mind, the St Gallen Consensus Conference aims to offer guidance to clinicians regarding appropriate treatments for early-stage breast cancer and assist in balancing the realistic trade-offs between treatment benefit and toxicity, enabling patients and clinicians to make well-informed choices through a shared decision-making process.

Circulating tumor DNA association with residual cancer burden after neoadjuvant chemotherapy in triple-negative breast cancer in TBCRC 030.

BACKGROUND: We aimed to examine circulating tumor DNA (ctDNA) and its association with residual cancer burden (RCB) using an ultrasensitive assay in patients with triple-negative breast cancer (TNBC) receiving neoadjuvant chemotherapy. PATIENTS AND METHODS: We identified responders (RCB 0/1) and matched non-responders (RCB 2/3) from the phase II TBCRC 030 prospective study of neoadjuvant paclitaxel versus cisplatin in TNBC. We collected plasma samples at baseline, 3 weeks and 12 weeks (end of therapy). We created personalized ctDNA assays utilizing MAESTRO mutation enrichment sequencing. We explored associations between ctDNA and RCB status and disease recurrence. RESULTS: Of 139 patients, 68 had complete samples and no additional neoadjuvant chemotherapy. Twenty-two were responders and 19 of those had sufficient tissue for whole-genome sequencing. We identified an additional 19 non-responders for a matched case-control analysis of 38 patients using a MAESTRO ctDNA assay tracking 319-1000 variants (median 1000 variants) to 114 plasma samples from 3 timepoints. Overall, ctDNA positivity was 100% at baseline, 79% at week 3 and 55% at week 12. Median tumor fraction (TFx) was 3.7 × 10-4 (range 7.9 × 10-7-4.9 × 10-1). TFx decreased 285-fold from baseline to week 3 in responders and 24-fold in non-responders. Week 12 ctDNA clearance correlated with RCB: clearance was observed in 10 of 11 patients with RCB 0, 3 of 8 with RCB 1, 4 of 15 with RCB 2 and 0 of 4 with RCB 3. Among six patients with known recurrence, five had persistent ctDNA at week 12. CONCLUSIONS: Neoadjuvant chemotherapy for TNBC reduced ctDNA TFx by 285-fold in responders and 24-fold in non-responders. In 58% (22/38) of patients, ctDNA TFx dropped below the detection level of a commercially available test, emphasizing the need for sensitive tests. Additional studies will determine whether ctDNA-guided approaches can improve outcomes.

ESMO expert consensus statements (ECS) on the definition, diagnosis, and management of HER2-low breast cancer.

Human epidermal growth factor receptor 2 (HER2)-low breast cancer has recently emerged as a targetable subset of breast tumors, based on the evidence from clinical trials of novel anti-HER2 antibody-drug conjugates. This evolution has raised several biological and clinical questions, warranting the establishment of consensus to optimally treat patients with HER2-low breast tumors. Between 2022 and 2023, the European Society for Medical Oncology (ESMO) held a virtual consensus-building process focused on HER2-low breast cancer. The consensus included a multidisciplinary panel of 32 leading experts in the management of breast cancer from nine different countries. The aim of the consensus was to develop statements on topics that are not covered in detail in the current ESMO Clinical Practice Guideline. The main topics identified for discussion were (i) biology of HER2-low breast cancer; (ii) pathologic diagnosis of HER2-low breast cancer; (iii) clinical management of HER2-low metastatic breast cancer; and (iv) clinical trial design for HER2-low breast cancer. The expert panel was divided into four working groups to address questions relating to one of the four topics outlined above. A review of the relevant scientific literature was conducted in advance. Consensus statements were developed by the working groups and then presented to the entire panel for further discussion and amendment before voting. This article presents the developed statements, including findings from the expert panel discussions, expert opinion, and a summary of evidence supporting each statement.

Risk-adapted modulation through de-intensification of cancer treatments: an ESMO classification.

BACKGROUND: The landscape of clinical trials testing risk-adapted modulations of cancer treatments is complex. Multiple trial designs, endpoints, and thresholds for non-inferiority have been used; however, no consensus or convention has ever been agreed to categorise biomarkers useful to inform the treatment intensity modulation of cancer treatments. METHODS: An expert subgroup under the European Society for Medical Oncology (ESMO) Precision Medicine Working Group shaped an international collaborative project to develop a classification system for biomarkers used in the cancer treatment de-intensification, based on a tiered approach. A group of disease-oriented clinical, translational, methodology and public health experts, and patients' representatives provided an analysis of the status quo, and scanned the horizon of ongoing clinical trials. The classification was developed through multiple rounds of expert revisions and inputs. RESULTS: The working group agreed on a univocal definition of treatment de-intensification. Evidence of reduction in the dose-density, intensity, or cumulative dose, including intermittent schedules or shorter treatment duration or deletion of segment(s) of the standard regimens, compound(s), or treatment modality must be demonstrated, to define a treatment de-intensification. De-intensified regimens must also portend a positive impact on toxicity, quality of life, health system burden, or financial toxicity. ESMO classification categorises the biomarkers for treatment modulation in three tiers, based on the level of evidence. Tier A includes biomarkers validated in prospective, randomised, non-inferiority clinical trials. The working group agreed that in non-inferiority clinical trials, boundaries are highly dependent upon the disease scenario and endpoint being studied and that the absolute differences in the outcomes are the most relevant measures, rather than relative differences. Biomarkers tested in single-arm studies with a threshold of non-inferiority are classified as Tier B. Tier C is when the validation occurs in prospective-retrospective quality cohort investigations. CONCLUSIONS: ESMO classification for the risk-guided intensity modulation of cancer treatments provides a set of evidence-based criteria to categorise biomarkers deemed to inform de-intensification of cancer treatments, in risk-defined patients. The classification aims at harmonising definitions on this matter, therefore offering a common language for all the relevant stakeholders, including clinicians, patients, decision-makers, and for clinical trials.

Continuous versus intermittent extended adjuvant letrozole for breast cancer: final results of randomized phase III SOLE (Study of Letrozole Extension) and SOLE Estrogen Substudy.

BACKGROUND: Late recurrences in postmenopausal women with hormone receptor-positive breast cancers remain an important challenge. Avoidance or delayed development of resistance represents the main objective in extended endocrine therapy (ET). In animal models, resistance was reversed with restoration of circulating estrogen levels during interruption of letrozole treatment. This phase III, randomized, open-label Study of Letrozole Extension (SOLE) studied the effect of extended intermittent letrozole treatment in comparison with continuous letrozole. In parallel, the SOLE estrogen substudy (SOLE-EST) analyzed the levels of estrogen during the interruption of treatment. PATIENTS AND METHODS: SOLE enrolled 4884 postmenopausal women with hormone receptor-positive, lymph node-positive, operable breast cancer between December 2007 and October 2012 and among them, 104 patients were enrolled in SOLE-EST. They must have undergone local treatment and have completed 4-6 years of adjuvant ET. Patients were randomized between continuous letrozole (2.5 mg/day orally for 5 years) and intermittent letrozole treatment (2.5 mg/day for 9 months followed by a 3-month interruption in years 1-4 and then 2.5 mg/day during all of year 5). RESULTS: Intention-to-treat population included 4851 women in SOLE (n = 2425 in the intermittent and n = 2426 in the continuous letrozole groups) and 103 women in SOLE-EST (n = 78 in the intermittent and n = 25 in the continuous letrozole groups). After a median follow-up of 84 months, 7-year disease-free survival (DFS) was 81.4% in the intermittent group and 81.5% in the continuous group (hazard ratio: 1.03, 95% confidence interval: 0.91-1.17). Reported adverse events were similar in both groups. Circulating estrogen recovery was demonstrated within 6 weeks after the stop of letrozole treatment. CONCLUSIONS: Extended adjuvant ET by intermittent administration of letrozole did not improve DFS compared with continuous use, despite the recovery of circulating estrogen levels. The similar DFS coupled with previously reported quality-of-life advantages suggest intermittent extended treatment is a valid option for patients who require or prefer a treatment interruption.

Customizing local and systemic therapies for women with early breast cancer: the St. Gallen International Consensus Guidelines for treatment of early breast cancer 2021.

The 17th St Gallen International Breast Cancer Consensus Conference in 2021 was held virtually, owing to the global COVID-19 pandemic. More than 3300 participants took part in this important bi-annual critical review of the 'state of the art' in the multidisciplinary care of early-stage breast cancer. Seventy-four expert panelists (see Appendix 1) from all continents discussed and commented on the previously elaborated consensus questions, as well as many key questions on early breast cancer diagnosis and treatment asked by the audience. The theme of this year's conference was 'Customizing local and systemic therapies.' A well-organized program of pre-recorded symposia, live panel discussions and real-time panel voting results drew a worldwide audience of thousands, reflecting the far-reaching impact of breast cancer on every continent. The interactive technology platform allowed, for the first time, audience members to ask direct questions to panelists, and to weigh in with their own vote on several key panel questions. A hallmark of this meeting was to focus on customized recommendations for treatment of early-stage breast cancer. There is increasing recognition that the care of a breast cancer patient depends on highly individualized clinical features, including the stage at presentation, the biological subset of breast cancer, the genetic factors that may underlie breast cancer risk, the genomic signatures that inform treatment recommendations, the extent of response before surgery in patients who receive neoadjuvant therapy, and patient preferences. This customized approach to treatment requires integration of clinical care between patients and radiology, pathology, genetics, and surgical, medical and radiation oncology providers. It also requires a dynamic response from clinicians as they encounter accumulating clinical information at the time of diagnosis and then serially with each step in the treatment plan and follow-up, reflecting patient experiences and treatment response.

Neoadjuvant treatment strategies for HER2-positive breast cancer: cost-effectiveness and quality of life outcomes.

PURPOSE: Achieving a pathologic complete response (pCR) with neoadjuvant therapy for HER2-positive breast cancer is associated with less recurrence and improved clinical outcomes compared to having residual cancer at surgery. However, recent data have demonstrated favorable outcomes for patients with residual HER2-positive cancer who received adjuvant trastuzumab emtansine (TDM-1). Therefore, we sought to determine the optimal chemotherapy/anti-HER2 treatment strategy. METHODS: We created a decision-analytic model for patients with stage II-III HER2-positive cancer that incorporated utilities based on toxicity and recurrence. We separately modeled hormone receptor-negative (HR-) and positive (HR+) disease and calculated quality-adjusted life years (QALYs) and costs through 5 years. Simulated patients received one of the following neoadjuvant treatments: three 'intensive' regimens (TCHP: docetaxel, carboplatin, trastuzumab, pertuzumab; THP + AC: taxol, trastuzumab, pertuzumab then doxorubicin and cyclophosphamide; THP: taxol, trastuzumab, pertuzumab) and two 'de-escalated' regimens (TH: taxol, trastuzumab; TDM-1) followed by adjuvant treatment based on pathologic response. RESULTS: Among 'intensive' neoadjuvant strategies, treatment with THP was more effective and less costly than TCHP or THP + AC. When 'de-escalated' strategies were included, TH became the most cost-effective. For HR-negative cancer, TH had 0.003 fewer quality-adjusted life years (QALYs) than THP but was less costly by $55,831, resulting in an incremental cost-effectiveness ratio of over $18M/QALY for THP, well above any threshold. For HR-positive cancer, neoadjuvant TH dominated the THP strategy. CONCLUSION: An adaptive-treatment strategy beginning with neoadjuvant THP or TH followed by tailoring post-operative therapy reduces treatment costs, and spares toxicity compared to more intensive chemotherapy regimens for women with HER2-positive breast cancer.

Estimating the benefits of therapy for early-stage breast cancer: the St. Gallen International Consensus Guidelines for the primary therapy of early breast cancer 2019.

BACKGROUND: The 16th St. Gallen International Breast Cancer Conference 2019 in Vienna, Austria reviewed substantial new evidence on loco-regional and systemic therapies for early breast cancer. DESIGN: Treatments were assessed in light of their intensity, duration and side-effects, estimating the magnitude of clinical benefit according to stage and biology of the disease. The Panel acknowledged that for many patients, the impact of adjuvant therapy or the adherence to specific guidelines may have modest impact on the risk of breast cancer recurrence or overall survival. For that reason, the Panel explicitly encouraged clinicians and patients to routinely discuss the magnitude of benefit for interventions as part of the development of the treatment plan. RESULTS: The guidelines focus on common ductal and lobular breast cancer histologies arising in generally healthy women. Special breast cancer histologies may need different considerations, as do individual patients with other substantial health considerations. The panelists' opinions reflect different interpretation of available data and expert opinion where is lack of evidence and sociocultural factors in their environment such as availability of and access to medical service, economic resources and reimbursement issues. Panelists encourage patient participation in well-designed clinical studies whenever available. CONCLUSIONS: With these caveats in mind, the St. Gallen Consensus Conference seeks to provide guidance to clinicians on appropriate treatments for early-stage breast cancer and guidance for weighing the realistic tradeoffs between treatment and toxicity so that patients and clinical teams can make well-informed decisions on the basis of an honest reckoning of the magnitude of clinical benefit.

A phase II feasibility study of palbociclib in combination with adjuvant endocrine therapy for hormone receptor-positive invasive breast carcinoma.

BACKGROUND: The CDK4/6 inhibitor palbociclib prolongs progression-free survival in hormone receptor-positive/HER2-negative (HR+/HER2-) metastatic breast cancer when combined with endocrine therapy. This phase II trial was designed to determine the feasibility of adjuvant palbociclib and endocrine therapy for early breast cancer. PATIENTS AND METHODS: Eligible patients with HR+/HER2- stage II-III breast cancer received 2 years of palbociclib at 125 mg daily, 3 weeks on/1 week off, with endocrine therapy. The primary end point was discontinuation from palbociclib due to toxicity, non-adherence, or events related to tolerability. A discontinuation rate of 48% or higher would indicate the treatment duration of 2 years was not feasible, and was evaluated under a binomial test using a one-sided α = 0.025. RESULTS: Overall, 162 patients initiated palbociclib; over half had stage III disease (52%) and most received prior chemotherapy (80%). A total of 102 patients (63%) completed 2 years of palbociclib; 50 patients discontinued early for protocol-related reasons (31%, 95% CI 24% to 39%, P = 0.001), and 10 discontinued due to protocol-unrelated reasons. The cumulative incidence of protocol-related discontinuation was 21% (95% CI 14% to 27%) at 12 months from start of treatment. Rates of palbociclib-related toxicity were congruent with the metastatic experience, and there were no cases of febrile neutropenia. Ninety-one patients (56%) required at least one dose reduction. CONCLUSION: Adjuvant palbociclib is feasible in early breast cancer, with a high proportion of patients able to complete 2 years of therapy. The safety profile in the adjuvant setting mirrors that observed in metastatic disease, with approximately half of the patients requiring dose-modification. As extended duration adjuvant palbociclib appears feasible and tolerable for most patients, randomized phase III trials are evaluating clinical benefit in this population. CLINICALTRIALS.GOV REGISTRATION: NCT02040857.

De-escalating and escalating treatments for early-stage breast cancer: the St. Gallen International Expert Consensus Conference on the Primary Therapy of Early Breast Cancer 2017.

The 15th St. Gallen International Breast Cancer Conference 2017 in Vienna, Austria reviewed substantial new evidence on loco-regional and systemic therapies for early breast cancer. Treatments were assessed in light of their intensity, duration and side-effects, seeking where appropriate to escalate or de-escalate therapies based on likely benefits as predicted by tumor stage and tumor biology. The Panel favored several interventions that may reduce surgical morbidity, including acceptance of 2 mm margins for DCIS, the resection of residual cancer (but not baseline extent of cancer) in women undergoing neoadjuvant therapy, acceptance of sentinel node biopsy following neoadjuvant treatment of many patients, and the preference for neoadjuvant therapy in HER2 positive and triple-negative, stage II and III breast cancer. The Panel favored escalating radiation therapy with regional nodal irradiation in high-risk patients, while encouraging omission of boost in low-risk patients. The Panel endorsed gene expression signatures that permit avoidance of chemotherapy in many patients with ER positive breast cancer. For women with higher risk tumors, the Panel escalated recommendations for adjuvant endocrine treatment to include ovarian suppression in premenopausal women, and extended therapy for postmenopausal women. However, low-risk patients can avoid these treatments. Finally, the Panel recommended bisphosphonate use in postmenopausal women to prevent breast cancer recurrence. The Panel recognized that recommendations are not intended for all patients, but rather to address the clinical needs of the majority of common presentations. Individualization of adjuvant therapy means adjusting to the tumor characteristics, patient comorbidities and preferences, and managing constraints of treatment cost and access that may affect care in both the developed and developing world.

Experts' perspectives on the role of medical marijuana in oncology: A semistructured interview study.

BACKGROUND: Expansion of medical marijuana (MM) laws in the United States may offer oncology new therapeutic options. However, the scientific evidence for MM remains in infancy. This study qualitatively explored professional opinion around the role of MM in cancer care. METHODS: Semistructured interviews were administered to a sample of individuals with expertise at the interface of MM and oncology nationally. Key informant criteria included an oncologic clinical or research background and any of the following: publications, research, or lectures on cannabinoids or cancer symptoms; involvement in the development of MM dispensaries or legislation; and early adoption of state MM certification procedures. A gold standard, grounded, inductive approach was used to identify underlying themes. RESULTS: Participants (N = 15) were predominantly male, in their sixth decade, working in academic settings. Themes ranged from strong beliefs in marijuana's medical utility to reservations about this notion, with calls for expansion of the scientific evidence base and more stringent MM production standards. All participants cited nausea as an appropriate indication, and 13 of 15 pain. Over one-third believed MM to have a more attractive risk profile than opioids and benzodiazepines. CONCLUSIONS: Expert opinion was divided between convictions in marijuana's medicinal potential and guardedness in this assertion, with no participant refuting MM's utility outright. Emergent themes included that MM ameliorates cancer-related pain and nausea and is safer than certain conventional medications. Participants called for enhanced purity and production standards, and further research on MM's utility.

Breast conservation following neoadjuvant therapy for breast cancer in the modern era: Are we losing the opportunity?

The main rationale for neoadjuvant therapy for breast cancer is to provide effective systemic treatment while surgically down-staging the cancer. This down-staging was initially to convert inoperable patients to operable and later to increase rates of breast conservation in patients initially deemed mastectomy only candidates. Unexpectedly, in recent neoadjuvant trials lower rates of breast conservation have been observed than in past decades, despite remarkable advances in systemic therapies, which have increased pathologic complete response rates. These results point to factors aside from response and eligibility for breast conservation that may lead surgeons and/or patients to recommend and choose mastectomy. Here, we aim to examine the surgical benefits offered by the modern era neoadjuvant therapy and explore factors that have contributed to this decrease in breast conservation rates. If the main benefit of neoadjuvant therapy is to increase the opportunity for breast conservation, then our review suggests that to optimize less invasive surgical approaches, we will need to address both surgeon and patient-level variables and biases that may be limiting our ability to identify patients appropriate for less aggressive options. As an oncology community, we must be aware of the surgical overtreatment of breast cancer, especially in a time where systemic therapies have remarkably improved outcomes and responses.