A prospective study of HER3 expression pre and post neoadjuvant therapy of different breast cancer subtypes: implications for HER3 imaging therapy guidance.

PURPOSE: HER3, a member of the EGFR receptor family, plays a central role in driving oncogenic cell proliferation in breast cancer. Novel HER3 therapeutics are showing promising results while recently developed HER3 PET imaging modalities aid in predicting and assessing early treatment response. However, baseline HER3 expression, as well as changes in expression while on neoadjuvant therapy, have not been well-characterized. We conducted a prospective clinical study, pre- and post-neoadjuvant/systemic therapy, in patients with newly diagnosed breast cancer to determine HER3 expression, and to identify possible resistance mechanisms maintained through the HER3 receptor. EXPERIMENTAL DESIGN: The study was conducted between May 25, 2018 and October 12, 2019. Thirty-four patients with newly diagnosed breast cancer of any subtype (ER ± , PR ± , HER2 ±) were enrolled in the study. Two core biopsy specimens were obtained from each patient at the time of diagnosis. Four patients underwent a second research biopsy following initiation of neoadjuvant/systemic therapy or systemic therapy which we define as neoadjuvant therapy. Molecular characterization of HER3 and downstream signaling nodes of the PI3K/AKT and MAPK pathways pre- and post-initiation of therapy was performed. Transcriptional validation of finings was performed in an external dataset (GSE122630). RESULTS: Variable baseline HER3 expression was found in newly diagnosed breast cancer and correlated positively with pAKT across subtypes (r = 0.45). In patients receiving neoadjuvant/systemic therapy, changes in HER3 expression were variable. In a hormone receptor-positive (ER +/PR +/HER2-) patient, there was a statistically significant increase in HER3 expression post neoadjuvant therapy, while there was no significant change in HER3 expression in a ER +/PR +/HER2+ patient. However, both of these patients showed increased downstream signaling in the PI3K/AKT pathway. One subject with ER +/PR -/HER2- breast cancer and another subject with ER +/PR +/HER2 + breast cancer showed decreased HER3 expression. Transcriptomic findings, revealed an immune suppressive environment in patients with decreased HER3 expression post therapy. CONCLUSION: This study demonstrates variable HER3 expression across breast cancer subtypes. HER3 expression can be assessed early, post-neoadjuvant therapy, providing valuable insight into cancer biology and potentially serving as a prognostic biomarker. Clinical translation of neoadjuvant therapy assessment can be achieved using HER3 PET imaging, offering real-time information on tumor biology and guiding personalized treatment for breast cancer patients.

Searching for the "Holy Grail" of breast cancer recurrence risk: a narrative review of the hunt for a better biomarker and the promise of circulating tumor DNA (ctDNA).

BACKGROUND: This paper is a narrative review of a major clinical challenge at the heart of breast cancer care: determining which patients are at risk of recurrence, which require systemic therapy, and which remain at risk in the survivorship phase of care despite initial therapy. METHODS: We review the literature on prognostic and predictive biomarkers in breast cancer with a focus on detection of minimal residual disease. RESULTS: While we have many tools to estimate and refine risk that are used to individualize local and systemic therapy, we know that we continue to over treat many patients and undertreat others. Many patients also experience what is, at least in hindsight, needless fear of recurrence. In this review, we frame this dilemma for the practicing breast oncologist and discuss the search for what we term the "holy grail" of breast cancer evaluation: the ideal biomarker of residual distant disease. We review the history of attempts to address this problem and the up-to-date science on biomarkers, circulating tumor cells and circulating tumor DNA (ctDNA). CONCLUSION: This review suggests that the emerging promise of ctDNA may help resolve a crticical dilemma at the heart of breast cancer care, and improve prognostication, treatment selection, and outcomes for patients with breast cancer.

Therapeutic Role of Tamoxifen for Triple-Negative Breast Cancer: Leveraging the Interaction Between ERß and Mutant p53.

The absence of effective therapeutic targets and aggressive nature of triple-negative breast cancer (TNBC) renders this disease subset difficult to treat. Although estrogen receptor beta (ERß) is expressed in TNBC, studies on its functional role have yielded inconsistent results. However, recently, our preclinical studies, along with other observations, have shown the potential therapeutic utility of ERß in the context of mutant p53 expression. The current case study examines the efficacy of the selective estrogen receptor modulator tamoxifen in p53-mutant TNBC with brain metastases. Significant increase in ERß protein expression and anti-proliferative interaction between mutant p53 and ERß were observed after cessation of tamoxifen therapy, with significant regression of brain metastases. This case study provides supporting evidence for the use of tamoxifen in p53-mutant, ERß+TNBC, especially in the setting of brain metastasis.

Feasibility of introducing a smartphone navigation application into the care of breast cancer patients (The FIONA Study).

PURPOSE: Patients with breast cancer (BC) face complex medical information and decisions. The Outcomes4Me mobile app provides evidence-based BC education, symptom management tracking and clinical trial matching. This study sought to evaluate the feasibility of introducing this app into routine BC care. METHODS: In this pilot study among BC patients undergoing therapy at an academic cancer center, patients were followed for 12 weeks with survey administration and electronic health record (EHR) abstraction at baseline and completion. Feasibility was defined as 40% of patients engaging with the app 3 or more times during the study. Additional endpoints included app usability (system usability scale), patient care experience, symptom evaluation, and clinical trial matching. RESULTS: The study enrolled 107 patients from 6/01/2020 to 3/31/2021. Utilization of the app was deemed feasible with 60% of patients engaging with the app at least 3 times. SUS score of 70 indicated above average usability. New diagnosis and higher education level was associated with greater app engagement, with usability similar across all age groups. 41% of patients found the app helped track symptoms. Cognitive and sexual symptoms were infrequently reported, but were more frequently captured in the app than in the EHR. After using the app, 33% of patients reported increased interest in clinical trial enrollment. CONCLUSION: Introducing the Outcomes4Me patient navigation app into routine BC care is feasible and may improve the patient experience. These results support further evaluation of this mobile technology platform to improve BC education, symptom management, and decision making. CLINICAL TRIAL REGISTRY: Clinicaltrials.gov registration #: NCT04262518.

Implementation and Clinical Adoption of Precision Oncology Workflows Across a Healthcare Network.

BACKGROUND: Precision oncology relies on molecular diagnostics, and the value-proposition of modern healthcare networks promises a higher standard of care across partner sites. We present the results of a clinical pilot to standardize precision oncology workflows. METHODS: Workflows are defined as the development, roll-out, and updating of disease-specific molecular order sets. We tracked the timeline, composition, and effort of consensus meetings to define the combination of molecular tests. To assess clinical impact, we examined order set adoption over a two-year period (before and after roll-out) across all gastrointestinal and hepatopancreatobiliary (GI) malignancies, and by provider location within the network. RESULTS: Development of 12 disease center-specific order sets took ~9 months, and the average number of tests per indication changed from 2.9 to 2.8 (P = .74). After roll-out, we identified significant increases in requests for GI patients (17%; P < .001), compliance with testing recommendations (9%; P < .001), and the fraction of "abnormal" results (6%; P < .001). Of 1088 GI patients, only 3 received targeted agents based on findings derived from non-recommended orders (1 before and 2 after roll-out); indicating that our practice did not negatively affect patient treatments. Preliminary analysis showed 99% compliance by providers in network sites, confirming the adoption of the order sets across the network. CONCLUSION: Our study details the effort of establishing precision oncology workflows, the adoption pattern, and the absence of harm from the reduction of non-recommended orders. Establishing a modifiable communication tool for molecular testing is an essential component to optimize patient care via precision oncology.

Sacituzumab Govitecan-hziy in Refractory Metastatic Triple-Negative Breast Cancer.

BACKGROUND: Standard chemotherapy is associated with low response rates and short progression-free survival among patients with pretreated metastatic triple-negative breast cancer. Sacituzumab govitecan-hziy is an antibody-drug conjugate that combines a humanized monoclonal antibody, which targets the human trophoblast cell-surface antigen 2 (Trop-2), with SN-38, which is conjugated to the antibody by a cleavable linker. Sacituzumab govitecan-hziy enables delivery of high concentrations of SN-38 to tumors. METHODS: We conducted a phase 1/2 single-group, multicenter trial involving patients with advanced epithelial cancers who received sacituzumab govitecan-hziy intravenously on days 1 and 8 of each 21-day cycle until disease progression or unacceptable toxic effects. A total of 108 patients received sacituzumab govitecan-hziy at a dose of 10 mg per kilogram of body weight after receiving at least two previous anticancer therapies for metastatic triple-negative breast cancer. The end points included safety; the objective response rate (according to Response Evaluation Criteria in Solid Tumors, version 1.1), which was assessed locally; the duration of response; the clinical benefit rate (defined as a complete or partial response or stable disease for at least 6 months); progression-free survival; and overall survival. Post hoc analyses determined the response rate and duration, which were assessed by blinded independent central review. RESULTS: The 108 patients with triple-negative breast cancer had received a median of 3 previous therapies (range, 2 to 10). Four deaths occurred during treatment; 3 patients (2.8%) discontinued treatment because of adverse events. Grade 3 or 4 adverse events (in ≥10% of the patients) included anemia and neutropenia; 10 patients (9.3%) had febrile neutropenia. The response rate (3 complete and 33 partial responses) was 33.3% (95% confidence interval [CI], 24.6 to 43.1), and the median duration of response was 7.7 months (95% CI, 4.9 to 10.8); as assessed by independent central review, these values were 34.3% and 9.1 months, respectively. The clinical benefit rate was 45.4%. Median progression-free survival was 5.5 months (95% CI, 4.1 to 6.3), and overall survival was 13.0 months (95% CI, 11.2 to 13.7). CONCLUSIONS: Sacituzumab govitecan-hziy was associated with durable objective responses in patients with heavily pretreated metastatic triple-negative breast cancer. Myelotoxic effects were the main adverse reactions. (Funded by Immunomedics; IMMU-132-01 ClinicalTrials.gov number, NCT01631552.).

Pilot study to assess prolonged overnight fasting in breast cancer survivors (longfast).

PURPOSE: Retrospective analysis of nightly fasting among women with breast cancer suggests that fasting < 13 h may be associated with a higher risk of breast cancer recurrence. We sought to evaluate prolonged overnight fasting (POF), an accessible nonpharmacological intervention, in a prospective feasibility study. METHODS: We designed a single-arm, pilot study to evaluate the feasibility of fasting for 13 h overnight for 12 weeks among women with a history of early-stage breast cancer survivors. Baseline and end of study assessments included measurements of body mass index (BMI), blood biomarkers, quality of life (QOL), mood, fatigue, and physical activity. Patient-reported outcome questionnaires were also administered at 6 weeks. Feasibility was defined as ≥ 60% of participants documenting fasting for 13 h on at least 70% of nights during the study period. RESULTS: Forty women with a history of breast cancer were enrolled with a median age of 60 (range 35-76) and median time since diagnosis of 4.5 years (range 0.8-20.7). At baseline, BMI was ≥ 25 in 37.5%. Ninety-five percent of participants fasted ≥ 13 h for at least 70% of study days (95% CI 83-99%). There was a statistically significant improvement in anxiety (p = 0.0007) at 6 weeks and BMI (p = 0.0072), anxiety (p = 0.0141), depression (p = 0.0048), and fatigue (p = 0.0105) at 12 weeks. There was no significant change in overall QOL, physical activity levels, or blood biomarkers at 12 weeks. CONCLUSIONS: POF is feasible among patients with a history of breast cancer and may potentially improve BMI, mood, and fatigue without detrimental effects on overall QOL.

Ipatasertib plus paclitaxel for PIK3CA/AKT1/PTEN-altered hormone receptor-positive HER2-negative advanced breast cancer: primary results from cohort B of the IPATunity130 randomized phase 3 trial.

PURPOSE: PI3K/AKT pathway alterations are frequent in hormone receptor-positive (HR+) breast cancers. IPATunity130 Cohort B investigated ipatasertib-paclitaxel in PI3K pathway-mutant HR+ unresectable locally advanced/metastatic breast cancer (aBC). METHODS: Cohort B of the randomized, double-blind, placebo-controlled, phase 3 IPATunity130 trial enrolled patients with HR+ HER2-negative PIK3CA/AKT1/PTEN-altered measurable aBC who were considered inappropriate for endocrine-based therapy (demonstrated insensitivity to endocrine therapy or visceral crisis) and were candidates for taxane monotherapy. Patients with prior chemotherapy for aBC or relapse < 1 year since (neo)adjuvant chemotherapy were ineligible. Patients were randomized 2:1 to ipatasertib (400 mg, days 1-21) or placebo, plus paclitaxel (80 mg/m2, days 1, 8, 15), every 28 days until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed progression-free survival (PFS). RESULTS: Overall, 146 patients were randomized to ipatasertib-paclitaxel and 76 to placebo-paclitaxel. In both arms, median investigator-assessed PFS was 9.3 months (hazard ratio, 1.00, 95% CI 0.71-1.40) and the objective response rate was 47%. Median paclitaxel duration was 6.9 versus 8.8 months in the ipatasertib-paclitaxel versus placebo-paclitaxel arms, respectively; median ipatasertib/placebo duration was 8.0 versus 9.1 months, respectively. The most common grade ≥ 3 adverse events were diarrhea (12% with ipatasertib-paclitaxel vs 1% with placebo-paclitaxel), neutrophil count decreased (9% vs 7%), neutropenia (8% vs 9%), peripheral neuropathy (7% vs 3%), peripheral sensory neuropathy (3% vs 5%) and hypertension (1% vs 5%). CONCLUSION: Adding ipatasertib to paclitaxel did not improve efficacy in PIK3CA/AKT1/PTEN-altered HR+ HER2-negative aBC. The ipatasertib-paclitaxel safety profile was consistent with each agent's known adverse effects. Trial registration NCT03337724.

The Evolving Role of Neoadjuvant Therapy for Operable Breast Cancer.

The role of neoadjuvant therapy (NAT) for localized breast cancer has evolved tremendously over the past several years. Currently, NAT is the preferred option for high-risk early triple-negative (TN) and HER2-positive (HER2+) breast cancers and is indicated for some estrogen receptor-positive (ER+) breast cancers. In addition to traditional absolute indications for NAT, relative indications such as the assessment of outcomes at the time of surgery and guidance of treatment escalation and de-escalation have greatly evolved in recent years. Pathologic complete response (pCR) and the Residual Cancer Burden (RCB) index are highly prognostic for disease recurrence and survival, mainly in patients with TN or HER2+ disease. Furthermore, post-NAT escalation strategies have been shown to improve long-term outcomes of patients who do not achieve pCR. Additionally, by allowing the direct assessment of drug effect on the tumor, the neoadjuvant setting has become an attractive setting for the exploration of novel agents and the identification of predictive biomarkers. Neoadjuvant trial design has also evolved, using adaptive treatment approaches that enable treatment de-escalation or escalation based on response. However, despite multiple practice-changing neoadjuvant trials and the addition of various new agents to the neoadjuvant setting for early breast cancer, many key questions remain. For example, patient selection for neoadjuvant immunotherapy in TN breast cancer, de-escalation methods in HER2+ breast cancer, and the use of gene expression profiles to guide NAT recommendations in ER+ breast cancer. This article reviews the current approach for NAT in localized breast cancer as well as evolving NAT strategies, the key remaining challenges, and the ongoing work in the field.

Breast Cancer, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology.

The therapeutic options for patients with noninvasive or invasive breast cancer are complex and varied. These NCCN Clinical Practice Guidelines for Breast Cancer include recommendations for clinical management of patients with carcinoma in situ, invasive breast cancer, Paget disease, phyllodes tumor, inflammatory breast cancer, and management of breast cancer during pregnancy. The content featured in this issue focuses on the recommendations for overall management of ductal carcinoma in situ and the workup and locoregional management of early stage invasive breast cancer. For the full version of the NCCN Guidelines for Breast Cancer, visit NCCN.org.

Final results of the double-blind placebo-controlled randomized phase 2 LOTUS trial of first-line ipatasertib plus paclitaxel for inoperable locally advanced/metastatic triple-negative breast cancer.

PURPOSE: In LOTUS (NCT02162719), adding the oral AKT inhibitor ipatasertib to first-line paclitaxel for locally advanced/metastatic triple-negative breast cancer (aTNBC) improved progression-free survival (PFS; primary endpoint), with an enhanced effect in patients with PIK3CA/AKT1/PTEN-altered tumors (FoundationOne next-generation sequencing [NGS] assay). We report final overall survival (OS) results. METHODS: Eligible patients had measurable previously untreated aTNBC. Patients were stratified by prior (neo)adjuvant therapy, chemotherapy-free interval, and tumor immunohistochemistry PTEN status, and were randomized 1:1 to paclitaxel 80 mg/m2 (days 1, 8, 15) plus ipatasertib 400 mg or placebo (days 1-21) every 28 days until disease progression or unacceptable toxicity. OS (intent-to-treat [ITT], immunohistochemistry PTEN-low, and PI3K/AKT pathway-activated [NGS PIK3CA/AKT1/PTEN-altered] populations) was a secondary endpoint. RESULTS: Median follow-up was 19.0 versus 16.0 months in the ipatasertib-paclitaxel versus placebo-paclitaxel arms, respectively. In the ITT population (n = 124), median OS was numerically longer with ipatasertib-paclitaxel than placebo-paclitaxel (hazard ratio 0.80, 95% CI 0.50-1.28; median 25.8 vs 16.9 months, respectively; 1-year OS 83% vs 68%). Likewise, median OS favored ipatasertib-paclitaxel in the PTEN-low (n = 48; 23.1 vs 15.8 months; hazard ratio 0.83) and PIK3CA/AKT1/PTEN-altered (n = 42; 25.8 vs 22.1 months; hazard ratio 1.13) subgroups. The ipatasertib-paclitaxel safety profile was unchanged. CONCLUSIONS: Final OS results show a numerical trend favoring ipatasertib-paclitaxel and median OS exceeding 2 years with ipatasertib-paclitaxel. Overall, results are consistent with the reported PFS benefit; interpretation within biomarker-defined subgroups is complicated by small sample sizes and TNBC heterogeneity.

A phase II study of efficacy, toxicity, and the potential impact of genomic alterations on response to eribulin mesylate in combination with trastuzumab and pertuzumab in women with human epidermal growth factor receptor 2 (HER2)+ metastatic breast cancer.

PURPOSE: There are limited data on trastuzumab-pertuzumab (HP)-based treatments beyond the first-line, HER2+ metastatic breast cancer (MBC) setting. We conducted a phase II study of eribulin mesylate, which extends survival in MBC, with HP in patients with previously treated HER2+ MBC to evaluate efficacy, toxicity, and genomic alterations driving therapeutic response. METHODS: After a run-in phase for eribulin dosing, two cohorts were enrolled (Cohort A-no prior pertuzumab; Cohort B-prior pertuzumab). All patients received eribulin 1.4 mg/m2 on days 1, 8 with standard-dose HP on day 1 (21-day cycles). The primary endpoint was objective response rate (ORR). Genomic characterization via whole exome sequencing (WES) was completed on tumor DNA and matched germline DNA from 19 patients. RESULTS: The six-patient run-in established a dose of eribulin 1.4 mg/m2 with HP. Cohorts A and B enrolled 17 and 7 patients, respectively. Accrual stopped early due to an evolving treatment landscape and slow enrollment. The ORR was 26.3% (95% Confidence Interval [CI] 9.2-51.2%) in Cohort A and 0% in Cohort B (95% CI 0-41.0%). WES revealed more frequent alterations in TP53 (p < 0.05, q > 0.05) in patients without clinical benefit (disease control for < 24 weeks) which was not significant after multiple hypothesis correction. CONCLUSION: Eribulin-HP had manageable toxicity and modest clinical activity in patients without prior pertuzumab exposure. This study provides a preliminary landscape of somatic alterations in this patient cohort. Our data add to the literature on how genomic alterations may predict for therapy response/resistance, as we work to individualize choices in a quickly evolving HER2+ MBC treatment landscape. TRIAL REGISTRATION: www.clinicaltrials.gov , NCT01912963. Registered 24 July 2013.

Phase II trial of veliparib and temozolomide in metastatic breast cancer patients with and without BRCA1/2 mutations.

PURPOSE: We evaluated the efficacy and safety of poly-(adenosine diphosphate-ribose) polymerase (PARP) 1 and 2 inhibitor veliparib and temozolomide in metastatic breast cancer patients with and without germline BRCA1/2 mutations. METHODS: In this single-arm phase II trial, patients with metastatic breast cancer received veliparib 30 to 40 mg twice daily on days 1 to 7 with concurrent temozolomide 150 mg/m2 on days 1 to 5 of a 28-day cycle. The primary cohort was unselected for BRCA mutation status, and an expansion cohort enrolled only BRCA1/2 carriers. The primary endpoint was objective response rate (ORR) in each cohort. Secondary endpoints included progression-free survival (PFS), clinical benefit rate (CBR), and evaluation of safety and tolerability. RESULTS: In the primary cohort of 41 unselected patients, which included 9 BRCA mutation carriers, the ORR was 10% and clinical benefit rate at 4 months (CBR) was 27%. In the expansion cohort of 21 BRCA1/2 carriers, the ORR was 14% and CBR was 43%. Among all 30 BRCA1/2 carriers, the ORR was 23% versus 0% among non-carriers. In the subset of BRCA1/2 carriers, the ORR was 32% among platinum-naïve patients versus 9% among platinum-exposed patients. The median PFS was 3.3 months among BRCA1/2 carriers compared to 1.8 months among non-carriers (HR: 0.48, p = 0.006). A longer median PFS of 6.2 months was observed among BRCA1/2 carriers who had no prior platinum therapy. The most common grade 3 and 4 toxicities were thrombocytopenia (32%) and neutropenia (21%) that generally improved with dose modifications. CONCLUSION: Veliparib and temozolomide demonstrated clinical activity in platinum-naïve BRCA-associated metastatic breast cancer with manageable toxicity at doses of veliparib well below the single-agent active dose. Although the study did not meet its primary endpoint in unselected nor BRCA-associated breast cancer, this regimen was further evaluated in the BROCADE 2 study. TRIAL REGISTRATION: NCT01009788 (ClinicalTrials.gov), November 9, 2009.

Chemotherapy-related amenorrhea (CRA) after adjuvant ado-trastuzumab emtansine (T-DM1) compared to paclitaxel in combination with trastuzumab (TH) (TBCRC033: ATEMPT Trial).

PURPOSE: Chemotherapy-related amenorrhea (CRA) is a surrogate for ovarian toxicity and associated risk of infertility and premature menopause. Here, we compare CRA rate with paclitaxel (T)-trastuzumab (H) to that with ado-trastuzumab emtansine (T-DM1). METHODS: Patients with T1N0 HER2 + early-stage breast cancer (eBC) enrolled on the ATEMPT trial and were randomized 3:1 to T-DM1 3.6 mg/kg IV every (q) 3 weeks (w) × 17 vs. T 80 mg/m2 with H IV qw × 12 (4 mg/kg load → 2 mg/kg), followed by H (6 mg/kg IV q3w × 13). Enrollees who self-reported as premenopausal were asked to complete menstrual surveys at baseline and every 6-12 months for 60 months. 18-month CRA (no periods reported during prior 6 months on 18-month survey) was the primary endpoint of this analysis. RESULTS: Of 512 ATEMPT enrollees, 123 who began protocol therapy and answered baseline and at least one follow-up menstrual survey were premenopausal at enrollment. 76 had menstrual data available at 18 months without having received a gonadotropin-releasing hormone agonist or undergone hysterectomy and/or oophorectomy. Median age was 45 (range 23-53) among 18 who had received TH and 46 (range 34-54) among 58 who had received T-DM1. The 18-month rate of CRA was 50% after TH and 24% after T-DM1 (p = 0.045). CONCLUSION: Amenorrhea at 18 months was less likely in recipients of adjuvant T-DM1 than TH. Future studies are needed to understand how T-DM1 impacts risk of infertility and permanent menopause, and to assess amenorrhea rates when T-DM1 is administered after standard HER2-directed chemotherapy regimens.

Clinical Outcomes With Abemaciclib After Prior CDK4/6 Inhibitor Progression in Breast Cancer: A Multicenter Experience.

BACKGROUND: Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) are widely used as first-line therapy for hormone receptor-positive metastatic breast cancer (HR+ MBC). Although abemaciclib monotherapy is also FDA-approved for treatment of disease progression on endocrine therapy, there is limited insight into the clinical activity of abemaciclib after progression on prior CDK4/6i. PATIENTS AND METHODS: We identified patients with HR+ MBC from 6 cancer centers in the United States who received abemaciclib after disease progression on prior CDK4/6i, and abstracted clinical features, outcomes, toxicity, and predictive biomarkers. RESULTS: In the multicenter cohort, abemaciclib was well tolerated after a prior course of CDK4/6i (palbociclib)-based therapy; a minority of patients discontinued abemaciclib because of toxicity without progression (9.2%). After progression on palbociclib, most patients (71.3%) received nonsequential therapy with abemaciclib (with ≥1 intervening non-CDK4/6i regimens), with most receiving abemaciclib with an antiestrogen agent (fulvestrant, 47.1%; aromatase inhibitor, 27.6%), and the remainder receiving abemaciclib monotherapy (19.5%). Median progression-free survival for abemaciclib in this population was 5.3 months and median overall survival was 17.2 months, notably similar to results obtained in the MONARCH-1 study of abemaciclib monotherapy in heavily pretreated HR+/HER2-negative CDK4/6i-naïve patients. A total of 36.8% of patients received abemaciclib for ≥6 months. There was no relationship between the duration of clinical benefit while on palbociclib and the subsequent duration of treatment with abemaciclib. RB1, ERBB2, and CCNE1 alterations were noted among patients with rapid progression on abemaciclib. CONCLUSIONS: A subset of patients with HR+ MBC continue to derive clinical benefit from abemaciclib after progression on prior palbociclib. These results highlight the need for future studies to confirm molecular predictors of cross-resistance to CDK4/6i therapy and to better characterize the utility of abemaciclib after disease progression on prior CDK4/6i.

NCCN Guidelines® Insights: Breast Cancer, Version 4.2021.

The NCCN Guidelines for Breast Cancer include up-to-date guidelines for clinical management of patients with carcinoma in situ, invasive breast cancer, Paget disease, phyllodes tumor, inflammatory breast cancer, male breast cancer, and breast cancer during pregnancy. These guidelines are developed by a multidisciplinary panel of representatives from NCCN Member Institutions with breast cancer-focused expertise in the fields of medical oncology, surgical oncology, radiation oncology, pathology, reconstructive surgery, and patient advocacy. These NCCN Guidelines Insights focus on the most recent updates to recommendations for adjuvant systemic therapy in patients with nonmetastatic, early-stage, hormone receptor-positive, HER2-negative breast cancer.

Convergent loss of PTEN leads to clinical resistance to a PI(3)Kα inhibitor.

Broad and deep tumour genome sequencing has shed new light on tumour heterogeneity and provided important insights into the evolution of metastases arising from different clones. There is an additional layer of complexity, in that tumour evolution may be influenced by selective pressure provided by therapy, in a similar fashion to that occurring in infectious diseases. Here we studied tumour genomic evolution in a patient (index patient) with metastatic breast cancer bearing an activating PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha, PI(3)Kα) mutation. The patient was treated with the PI(3)Kα inhibitor BYL719, which achieved a lasting clinical response, but the patient eventually became resistant to this drug (emergence of lung metastases) and died shortly thereafter. A rapid autopsy was performed and material from a total of 14 metastatic sites was collected and sequenced. All metastatic lesions, when compared to the pre-treatment tumour, had a copy loss of PTEN (phosphatase and tensin homolog) and those lesions that became refractory to BYL719 had additional and different PTEN genetic alterations, resulting in the loss of PTEN expression. To put these results in context, we examined six other patients also treated with BYL719. Acquired bi-allelic loss of PTEN was found in one of these patients, whereas in two others PIK3CA mutations present in the primary tumour were no longer detected at the time of progression. To characterize our findings functionally, we examined the effects of PTEN knockdown in several preclinical models (both in cell lines intrinsically sensitive to BYL719 and in PTEN-null xenografts derived from our index patient), which we found resulted in resistance to BYL719, whereas simultaneous PI(3)K p110ß blockade reverted this resistance phenotype. We conclude that parallel genetic evolution of separate metastatic sites with different PTEN genomic alterations leads to a convergent PTEN-null phenotype resistant to PI(3)Kα inhibition.

The adjuvant use of capecitabine for residual disease following pre-operative chemotherapy for breast cancer: Challenges applying CREATE-X to a US population.

INTRODUCTION: The CREATE-X study, conducted in Japan and South Korea, established capecitabine as an adjuvant treatment option for patients with triple negative breast cancer (TNBC) who have residual disease (RD) following neoadjuvant anthracycline or taxane-based chemotherapy. However, there are no reports on the tolerability and outcomes of adjuvant capecitabine in the US setting following publication of the CREATE-X data. METHODS: We retrospectively collected treatment and tolerability data from the medical records of the first 23 TNBC patients who received adjuvant capecitabine for RD post neoadjuvant chemotherapy at our institution. Disease-free survival was assessed using the Kaplan-Meier method. RESULTS: The median starting dosage of capecitabine was 1871 mg/m2/day, most commonly divided into two daily doses on days 1-14 of each 21 day cycle. 34.8% of patients completed the treatment as prescribed. Side effects associated with treatment were common with 69.6% of patients experiencing hand-foot syndrome, 39.1% of patients experiencing diarrhea, and 13.0% of patients requiring hospitalization for side effects. Of 23 patients treated with adjuvant capecitabine, 34.8% completed the planned dose, 30.4% completed with dose reduction, and 34.8% discontinued early. At a median follow-up time of 14 months, the median disease-free survival was 22 months, with 30.4% of patients experiencing recurrence. CONCLUSION: Tolerability was poor overall compared to the CREATE-X cohort. Administering adjuvant capecitabine for TNBC patients with residual disease in the United States is challenging given differences in tolerability. More research is needed to understand how poor tolerability will affect the efficacy of this approach in the US population.

A Phase II Trial of Cabozantinib in Hormone Receptor-Positive Breast Cancer with Bone Metastases.

BACKGROUND: We assessed the antitumor activity of cabozantinib, a potent multireceptor oral tyrosine kinase inhibitor, in patients with hormone receptor-positive breast cancer with bone metastases. PATIENTS AND METHODS: In this single-arm multicenter phase II study, patients received an initial starting dose of 100 mg, later reduced to 60 mg, per day. The primary endpoint was the bone scan response rate. Secondary endpoints included objective response rate by RECIST, progression-free survival (PFS), and overall survival (OS). RESULTS: Of 52 women enrolled, 20 (38%) experienced a partial response on bone scan and 6 (12%) had stable disease. Prior to the first repeat bone scan at 12 weeks, 19 (35%) patients discontinued study treatment because of early clinical progression or unacceptable toxicity. RECIST evaluation based on best overall response by computed tomography revealed stable disease in extraosseous tissues in 26 patients (50%) but no complete or partial responses. In 25 patients with disease control on bone scan at 12 weeks, only 3 (12%) patients developed extraosseous progression. The median PFS was 4.3 months, and median OS was 19.6 months. The most common grade 3 or 4 toxicities were hypertension (10%), anorexia (6%), diarrhea (6%), fatigue (4%), and hypophosphatemia (4%). CONCLUSION: Bone scans improved in 38% of patients with metastatic hormone receptor-positive breast cancer and remained stable in an additional 12% for a minimum duration of 12 weeks on cabozantinib. Further investigations should assess the activity of cabozantinib in combination with other hormonal and other breast cancer therapies and determine whether bone scan responses correlate with meaningful antitumor effects. ClinicalTrials.gov identifier. NCT01441947 IMPLICATIONS FOR PRACTICE: Most patients with metastatic hormone receptor-positive (HR+) breast cancer have bone involvement, and many have bone-only disease, which is difficult to evaluate for response. This phase II single-arm study evaluated the clinical activity of the small molecule MET/RET/VEGFR2 inhibitor cabozantinib in patients with metastatic HR+ breast cancer with bone metastases. This study met its primary endpoint, and cabozantinib treatment resulted in a significant bone scan response rate correlating with improved survival. This is the first study to use bone scan response as a primary endpoint in breast cancer. The results support further study of cabozantinib in HR+ breast cancer.

A system for risk stratification and prioritization of breast cancer surgeries delayed by the COVID-19 pandemic: preparing for re-entry.

PURPOSE: During the COVID-19 pandemic, most breast surgery for benign and malignant conditions has been postponed, creating a backlog of patients who will need surgery. A fair and transparent system for assessing the risk of further delaying surgery for individual patients to prioritize surgical scheduling is needed. METHODS: Factors related to risk of delaying surgery for breast patients were identified. Scores were assigned to each factor, with higher scores indicating a greater risk from delaying surgery. REDCap and Microsoft Excel tools were designed to track and score delayed patients. RESULTS: Published data and multidisciplinary clinical judgement were used to assign risk scores based on patient and tumor factors, length of delay, and tumor response to preoperative therapy. Patients completing neoadjuvant chemotherapy were assigned the highest scores as their options for delaying surgery are most limited. Among patients receiving neoadjuvant endocrine therapy or no medical therapy, higher scores were assigned for low-estrogen receptor or high-genomic risk scores, higher grade, larger tumors, younger age and longer delay. High priority scores were assigned for progression during preoperative therapy. Low scores were assigned for re-excisions, atypical lesions and other benign indications. There was good agreement of the tool's ranking of sample patients with rankings by experienced clinicians. The tool generates risk-stratified patient lists by surgeon or institution to facilitate assignment of surgery dates. CONCLUSIONS: This tool generates a clinically consistent, risk-stratified priority list of breast surgical procedures delayed by the COVID-19 pandemic. This systematic approach may facilitate surgical scheduling as conditions normalize.