Real-world use patterns, effectiveness, and tolerability of sacituzumab govitecan for second-line and later-line treatment of metastatic triple-negative breast cancer in the United States.

PURPOSE: Patients with metastatic triple-negative breast cancer (mTNBC) have poor prognosis and limited treatment options. Sacituzumab govitecan (SG), a Trop-2-directed antibody-drug conjugate, is approved for patients with mTNBC who have received ≥ 2 systemic therapies (≥ 1 in the metastatic setting) based on the ASCENT study (NCT02574455). The current study describes real-world SG use and outcomes in patients with mTNBC in the United States. METHODS: This retrospective, observational study included adult patients with mTNBC from the ConcertAI Patient360™ database who received SG in the second line (2L) and later from April 2020 to May 2022. SG use patterns, effectiveness, and tolerability are described. RESULTS: This analysis included 230 patients (median age 60 years, 26% Black, 17% with ECOG performance status ≥ 2, 66% in community settings; median of 2 prior lines of treatment in the metastatic setting); median follow-up was 7.2 months. Median (95% CI) real-world overall survival was 10.0 (8.3-11.1) months for all patients and 13.9 (9.8-not estimable) months in the 2L subgroup (n = 77). Granulocyte-colony stimulating factor (G-CSF) was administered concomitantly with SG in 134 (58%) patients; 35 (15%) received G-CSF for the first time. Median (IQR) time from SG start to G-CSF use was 8.5 (8.0-29.0) days. Seventeen (7%) patients discontinued SG due to toxicity. CONCLUSIONS: Using a real-world, ethnically diverse population of patients with mTNBC presenting with poor prognosis, these data reinforced the findings from ASCENT. In routine clinical practice, SG is an effective treatment in the 2L setting, consistent with treatment guidelines.

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.

Clinical Implications and Treatment Strategies for ESR1 Fusions in Hormone Receptor-Positive Metastatic Breast Cancer: A Case Series.

In hormone receptor-positive metastatic breast cancer (HR+ MBC), endocrine resistance is commonly due to genetic alterations of ESR1, the gene encoding estrogen receptor alpha (ERα). While ESR1 point mutations (ESR1-MUT) cause acquired resistance to aromatase inhibition (AI) through constitutive activation, far less is known about the molecular functions and clinical consequences of ESR1 fusions (ESR1-FUS). This case series discusses 4 patients with HR+ MBC with ESR1-FUS in the context of the existing ESR1-FUS literature. We consider therapeutic strategies and raise the hypothesis that CDK4/6 inhibition (CDK4/6i) may be effective against ESR1-FUS with functional ligand-binding domain swaps. These cases highlight the importance of screening for ESR1-FUS in patients with HR+ MBC while continuing investigation of precision treatments for these genomic rearrangements.

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.

Endocrine Therapy for Surgeons: Practical Pearls for Managing Menopausal, Bone Loss and Sexual Adverse Effects.

Breast cancer patients are living longer than ever before and as such the population of breast cancer survivors continues to grow. Approximately 80% of breast cancers are hormone receptor-positive (HR+) and most patients will receive neoadjuvant or adjuvant estrogen blockade, referred to as endocrine therapy. Although endocrine therapy reduces HR+ breast cancer recurrence by 30-50%, significant adverse effects pose a threat to treatment adherence. These adverse effects include vasomotor symptoms, colloquially referred to as hot flashes, bone loss, joint arthralgias, genitourinary syndrome of menopause (GSM), previously referred to as vaginal atrophy, and low libido. This review will present the evidence-based treatments available for each of these adverse effects, including clear treatment algorithms for GSM, which is often experienced by patients but overlooked by providers. The most important takeaway is to ask open-ended questions, encourage reporting of these symptoms, and refer patients to specialty providers as needed. Surgeons may be the first to encounter these symptoms, therefore it is critical to remain informed of the treatment options.

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.

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.

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.

ESR1 mutation as an emerging clinical biomarker in metastatic hormone receptor-positive breast cancer.

In metastatic hormone receptor-positive breast cancer, ESR1 mutations are a common cause of acquired resistance to the backbone of therapy, estrogen deprivation by aromatase inhibition. How these mutations affect tumor sensitivity to established and novel therapies are active areas of research. These therapies include estrogen receptor-targeting agents, such as selective estrogen receptor modulators, covalent antagonists, and degraders (including tamoxifen, fulvestrant, and novel agents), and combination therapies, such as endocrine therapy plus CDK4/6, PI3K, or mTORC1 inhibition. In this review, we summarize existing knowledge surrounding the mechanisms of action of ESR1 mutations and roles in resistance to aromatase inhibition. We then analyze the recent literature on how ESR1 mutations affect outcomes in estrogen receptor-targeting and combination therapies. For estrogen receptor-targeting therapies such as tamoxifen and fulvestrant, ESR1 mutations cause relative resistance in vitro but do not clearly lead to resistance in patients, making novel agents in this category promising. Regarding combination therapies, ESR1 mutations nullify any aromatase inhibitor component of the combination. Thus, combinations using endocrine alternatives to aromatase inhibition, or combinations where the non-endocrine component is efficacious as monotherapy, are still effective against ESR1 mutations. These results emphasize the importance of investigating combinatorial resistance, challenging as these efforts are. We also discuss future directions and open questions, such as studying the differences among distinct ESR1 mutations, asking how to adjust clinical decisions based on molecular surveillance testing, and developing novel therapies that are effective against ESR1 mutations.

Cyclin-dependent kinase 4 and 6 inhibitors for hormone receptor-positive breast cancer: past, present, and future.

The development and approval of cyclin-dependent kinase (CDK) 4 and 6 inhibitors for hormone receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer represents a major milestone in cancer therapeutics. Three different oral CDK4/6 inhibitors, palbociclib, ribociclib, and abemaciclib, have significantly improved progression-free survival by a number of months when combined with endocrine therapy. More recently, improvement in overall survival has been reported with ribociclib and abemaciclib. The toxicity profile of all three drugs is well described and generally easily manageable with dose reductions when indicated. More myelotoxicity is observed with palbociclib and ribociclib, but more gastrointestinal toxicity is observed with abemaciclib. Emerging data is shedding light on the resistance mechanisms associated with CDK4/6 inhibitors, including cell cycle alterations and activation of upstream tyrosine kinase receptors. A number of clinical trials are exploring several important questions regarding treatment sequencing, combinatorial strategies, and the use of CDK4/6 inhibitors in the adjuvant and neoadjuvant settings, thereby further expanding and refining the clinical application of CDK4/6 inhibitors for patients with breast cancer.

Sacituzumab Govitecan for Metastatic Triple-Negative Breast Cancer: Clinical Overview and Management of Potential Toxicities.

Patients with metastatic triple-negative breast cancer have a poor prognosis. Sacituzumab govitecan (IMMU-132) is an antibody-drug conjugate that contains the irinotecan active metabolite, SN-38, linked to a humanized monoclonal antibody targeting trophoblast cell surface antigen 2, which is overexpressed in many solid tumors. In a basket design phase I/II study, sacituzumab govitecan demonstrated promising single-agent therapeutic activity in multiple cancer cohorts, leading to accelerated approval by the U.S. Food and Drug Administration of sacituzumab govitecan-hziy (TRODELVY) for the treatment of patients with metastatic triple-negative breast cancer who had received at least two prior therapies in the metastatic setting. Recently, results of the phase III trial, ASCENT, were confirmatory. There is limited available information on the adverse event management with sacituzumab govitecan needed to maximize the dose and duration of effective therapy while maintaining patient quality of life. This review summarizes the clinical development and the practical management of patients receiving sacituzumab govitecan. Sacituzumab govitecan has a well-defined and manageable toxicity profile, and rapid recognition and appropriate early and proactive management will allow clinicians to optimize sacituzumab govitecan treatment for patients. IMPLICATIONS FOR PRACTICE: Sacituzumab govitecan (TRODELVY) is a novel antibody-drug conjugate composed of the active metabolite of irinotecan (SN-38) conjugated to a monoclonal antibody targeting trophoblast cell surface antigen 2, an epithelial cell surface antigen overexpressed in many cancers. Because of the rapid approval of sacituzumab govitecan, there is limited available information on adverse event (AE) management with this agent. As such, this article reviews the clinical development of the drug, the AE profile, and provides recommendations regarding AE management to help optimize therapy with sacituzumab govitecan.

Locally Recurrent Secretory Carcinoma of the Breast with NTRK3 Gene Fusion.

Enhanced understanding of the molecular events underlying oncogenesis has led to the development of "tumor-agnostic" treatment strategies, which aim to target a tumor's genomic profile regardless of its anatomic site of origin. A classic example is the translocation resulting in an ETV6-NTRK3 gene fusion, a characteristic driver of a histologically diverse array of cancers. The chimeric ETV6-NTRK3 fusion protein elicits constitutive activation of the tropomyosin receptor kinase (TRK) C protein, leading to increased cell survival, growth, and proliferation. Two TRK inhibitors, larotrectinib and entrectinib, are currently approved for use in the metastatic setting for the treatment of advanced solid tumors harboring NTRK fusions. Here we report a rare case of recurrent secretory carcinoma of the breast (SCB) with NTRK3 gene fusion. Whereas most cases of SCB represent slow-growing tumors with favorable outcomes, the case detailed here is the first to the authors' knowledge of recurrence within 1 year of surgery. We review the molecular findings and potential clinical significance. KEY POINTS: The translocation resulting in the ETV6-NTRK3 gene fusion is a known oncogenic driver characteristic of secretory carcinoma of the breast (SCB). Whereas most cases of SCB represent slow-growing tumors with favorable outcomes, the case here with ETV6-NTRK3 gene fusion had local recurrence within 1 year of surgery. Two tropomyosin receptor kinase (TRK) inhibitors, larotrectinib and entrectinib, are approved to treat NTRK fusion-positive tumors, demonstrating sustained high overall response rates in the metastatic setting. Approval of TRK inhibitors necessitates optimization of NTRK fusion detection assays, including detection with liquid biopsies.

Management and outcomes of men diagnosed with primary breast cancer.

BACKGROUND: Fewer than 1% of all breast cancers occur in men. As a result, a distinct lack of data exists regarding the management and outcomes in this cohort. METHODS: Any male patient with pathologically confirmed breast cancer diagnosed between August 2000 and October 2017 at either Massachusetts General Hospital or Brigham and Women's Hospital/Dana-Farber Cancer Institute and their affiliate satellite locations were included. Primary chart review was used to assess clinical and pathologic characteristics. Patient and treatment variables were reported via descriptive statistics. Local-regional failure (LRF), overall survival (OS), breast cancer-specific survival (BCSS), and disease-free survival (DFS) were estimated using the Kaplan-Meier method. RESULTS: 100 patients were included in this study. Median follow-up was 112 months (range 1-220 months). Approximately 1/3 of patients experienced at least a 3-month delay to presentation. 83 patients ultimately underwent mastectomy as definitive surgical treatment. 46 patients received adjuvant radiation therapy, and 37 patients received chemotherapy. Of 82 hormone receptor-positive patients with invasive cancer, 94% (n = 77) received endocrine therapy. Of the fifty-eight patients who underwent genetic testing, 15 (26%) tested positive. The 5-year OS, BCSS, DFS, and LRF rates were 91.5%, 96.2%, 86%, and 4.8%, respectively. Delay to presentation was not associated with worse survival. CONCLUSIONS: Male breast cancer remains a rare diagnosis. Despite this, the majority of patients in this study received standard of care therapy and experienced excellent oncologic outcomes. Penetration for genetic testing improved over time.

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.

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 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.

Pathologic evaluation of response to neoadjuvant therapy drives treatment changes and improves long-term outcomes for breast cancer patients.

Systemic therapy for breast cancer may be given before (neoadjuvant) or after (adjuvant) surgery. When neoadjuvant systemic therapy is given, response to treatment can be evaluated. However, some prognostic information (for example, pathologic tumor size pretreatment) is then lost and pathologic evaluation of breast specimens after neoadjuvant therapy is more difficult. Pathologic complete response (pCR), defined as no invasive disease in the breast (ypT0/is or ypT0) and no disease in all sampled lymph nodes (ypN0), identifies patients with a lower risk of recurrence or death compared to those with residual disease. Multidisciplinary collaboration, marking of the tumor site and any lymph node involvement pretreatment, and access to specimen imaging to facilitate correlation of gross and microscopic findings are critical for accurate determination of pCR. For HER2-positive and triple negative tumors requiring systemic therapy, giving the treatment before surgery identifies a high-risk group of patients that can receive additional adjuvant therapy after surgery if a pCR is not achieved. Recent clinical trials have demonstrated that this approach reduced recurrence risk. More than ever, pathologic evaluation of response to neoadjuvant systemic therapy directs treatment received after surgery. Using a single standardized protocol for sampling of the post-neoadjuvant surgical specimen allows pathologists to ensure accurate determination of pCR or residual disease and quantify residual disease. Residual cancer burden (RCB) and AJCC stage provide complementary quantitative information about residual disease and prognosis.

CDK 4/6 Inhibitors in Breast Cancer: Current Controversies and Future Directions.

PURPOSE OF REVIEW: To describe the clinical role of CDK 4/6 inhibitors in hormone receptor-positive (HR+) metastatic breast cancer (HR+ MBC) as well as current controversies and evolving areas of research. RECENT FINDINGS: Palbociclib, ribociclib, and abemaciclib are each approved in combination with an aromatase inhibitor or fulvestrant for HR+ MBC. Abemaciclib is also approved as monotherapy for pre-treated patients. Key questions in the field include whether all patients with HR+ MBC should receive a CDK 4/6 inhibitor up front versus later line, impact on overall survival, role of continued CDK 4/6 blockade, mechanism of clinical resistance, and treatment sequencing. The development of CDK 4/6 inhibitors has changed the therapeutic management of HR+ MBC. Additional research is needed to determine optimal treatment sequencing, understand mechanisms governing resistance, and develop novel therapeutic strategies to circumvent or overcome clinical resistance and further improve the outcomes of patients with MBC.

Effectiveness and tolerability of neoadjuvant pertuzumab-containing regimens for HER2-positive localized breast cancer.

PURPOSE: Based on improvement in pathologic complete response (pCR) in the NeoSphere and TRYPHAENA studies, the FDA approved neoadjuvant pertuzumab for HER2+ localized breast cancer. These studies demonstrated high pCR rates with THP (docetaxel + HP), FEC (5-fluorouracil, epirubicin, and cyclophosphamide)-THP, and TCHP (docetaxel, carboplatin + HP). However, in the United States, doxorubicin/cyclophosphamide (AC) is favored over FEC despite no data comparing neoadjuvant AC-THP with AC-TH or TCHP. Here we report outcomes for patients with localized HER2+ breast cancer treated with pertuzumab-containing neoadjuvant regimens and AC-TH. METHODS: We reviewed clinicopathological characteristics of patients with HER2+ breast cancer (Stage I-III) treated with either a neoadjuvant pertuzumab-containing regimen or dose-dense (dd) AC-TH, from 2011 to 2016 at a large academic medical institution and two affiliated community sites. pCR was defined as ypT0/is ypN0. Fisher's exact test and logistic regression analysis were used for statistical analysis. RESULTS: In this study (N = 121), pCR was numerically higher with pertuzumab-based regimens, including ddAC-THP (60%), TCHP (63%), THP (55%), as compared with ddAC-TH (46%). THP resulted in significantly less cycle delays due to toxicity compared to the other regimens (p = 0.02). THP also resulted in the least dose reductions, lowest rate of hospitalization, and lowest rate of treatment discontinuation. CONCLUSIONS: Pertuzumab-based regimens, including THP, resulted in higher pCR rates as compared to ddAC-TH, with the THP regimen associated with the best tolerability among patients with localized HER2+ breast cancer. Given the various neoadjuvant regimens, additional studies are needed to determine optimal treatment sequencing and escalation/de-escalation strategies to personalize neoadjuvant regimens for localized HER2+ breast cancer.