Clinical trials in older patients with cancer - typical challenges, possible solutions, and a paradigm of study design in breast cancer.

BACKGROUND AND PURPOSE: While the prevalence of older breast cancer patients is rapidly increasing, these patients are greatly underrepresented in clinical trials. We discuss barriers to recruitment of older patients to clinical trials and propose solutions on how to mitigate these challenges and design optimal clinical trials through the paradigm of IMPORTANT trial. PATIENTS AND METHODS: This is a narrative review of the current literature evaluating barriers to including older breast cancer patients in clinical trials and how mitigating strategies can be implemented in a pragmatic clinical trial. RESULTS: The recognized barriers can be roughly divided into trial design-related (e.g. the adoption of strict inclusion criteria, the lack of pre-specified age-specific analysis), patient-related (e.g. lack of knowledge, valuation of the quality-of-life instead of survival, transportation issues), or physician-related (e.g. concern for toxicity). Several strategies to mitigate barriers have been identified and should be considered when designing a clinical trial dedicated to older patients with cancer. The pragmatic, de-centralized IMPORTANT trial focusing on dose optimization of CDK4/6 -inhibitors in older breast cancer patients is a paradigm of a study design where different mitigating strategies have been adopted. INTERPRETATION: Because of the existing barriers, older adults in clinical trials are considerably healthier than the average older patients treated in clinical practice. Thus, the study results cannot be generalized to the older population seen in daily clinical practice. Broader inclusion/exclusion criteria, offering telehealth visits, and inclusion of patient-reported, instead of physician-reported outcomes may increase older patient participation in clinical trials.

Circulating tumor cells and palbociclib treatment in patients with ER-positive, HER2-negative advanced breast cancer: results from a translational sub-study of the TREnd trial.

BACKGROUND: Circulating tumor cells (CTCs) are prognostic in patients with advanced breast cancer (ABC). However, no data exist about their use in patients treated with palbociclib. We analyzed the prognostic role of CTC counts in patients enrolled in the cTREnd study, a pre-planned translational sub-study of TREnd (NCT02549430), that randomized patients with ABC to palbociclib alone or palbociclib plus the endocrine therapy received in the prior line of treatment. Moreover, we evaluated RB1 gene expression on CTCs and explored its prognostic role within the cTREnd subpopulation. METHODS: Forty-six patients with ER-positive, HER2-negative ABC were analyzed. Blood samples were collected before starting palbociclib treatment (timepoint T0), after the first cycle of treatment (timepoint T1), and at disease progression (timepoint T2). CTCs were isolated and counted by CellSearch® System using the CellSearch™Epithelial Cell kit. Progression-free survival (PFS), clinical benefit (CB) during study treatment, and time to treatment failure (TTF) after study treatment were correlated with CTC counts. Samples with ≥ 5 CTCs were sorted by DEPArray system® (DA). RB1 and GAPDH gene expression levels were measured by ddPCR. RESULTS: All 46 patients were suitable for CTCs analysis. CTC count at T0 did not show significant prognostic value in terms of PFS and CB. Patients with at least one detectable CTC at T1 (n = 26) had a worse PFS than those with 0 CTCs (n = 16) (p = 0.02). At T1, patients with an increase of at least three CTCs showed reduced PFS compared to those with no increase (mPFS = 3 versus 9 months, (p = 0.004). Finally, patients with ≥ 5 CTCs at T2 (n = 6/23) who received chemotherapy as post-study treatment had a shorter TTF (p = 0.02). Gene expression data for RB1 were obtained from 19 patients. CTCs showed heterogeneous RB1 expression. Patients with detectable expression of RB1 at any timepoint showed better, but not statistically significant, outcomes than those with undetectable levels. CONCLUSIONS: CTC count seems to be a promising modality in monitoring palbociclib response. Moreover, CTC count at the time of progression could predict clinical outcome post-palbociclib. RB1 expression analysis on CTCs is feasible and may provide additional prognostic information. Results should be interpreted with caution given the small studied sample size.

Precision Oncology via NMR-Based Metabolomics: A Review on Breast Cancer.

Precision oncology is an emerging approach in cancer care. It aims at selecting the optimal therapy for the right patient by considering each patient's unique disease and individual health status. In the last years, it has become evident that breast cancer is an extremely heterogeneous disease, and therefore, patients need to be appropriately stratified to maximize survival and quality of life. Gene-expression tools have already positively assisted clinical decision making by estimating the risk of recurrence and the potential benefit from adjuvant chemotherapy. However, these approaches need refinement to further reduce the proportion of patients potentially exposed to unnecessary chemotherapy. Nuclear magnetic resonance (NMR) metabolomics has demonstrated to be an optimal approach for cancer research and has provided significant results in BC, in particular for prognostic and stratification purposes. In this review, we give an update on the status of NMR-based metabolomic studies for the biochemical characterization and stratification of breast cancer patients using different biospecimens (breast tissue, blood serum/plasma, and urine).

EFFECT: a randomized phase II study of efficacy and impact on function of two doses of nab-paclitaxel as first-line treatment in older women with advanced breast cancer.

BACKGROUND: Limited data are available regarding the use of nab-paclitaxel in older patients with breast cancer. A weekly schedule is recommended, but there is a paucity of evidence regarding the optimal dose. We evaluated the efficacy of two different doses of weekly nab-paclitaxel, with a specific focus on their corresponding impact on patient function, in order to address the lack of data specifically relating to the older population. METHODS: EFFECT is an open-label, phase II trial wherein 160 women with advanced breast cancer aged ≥ 65 years were enrolled from 15 institutions within Italy. Patients were randomly assigned 1:1 to receive nab-paclitaxel 100 mg/m2 (arm A) or 125 mg/m2 (arm B) on days 1, 8, and 15 on a 28-day cycle, as first-line treatment for advanced disease. The primary endpoint was event-free survival (EFS), wherein an event was defined as disease progression (PD), functional decline (FD), or death. In each arm, the null hypothesis that the median EFS would be ≤ 7 months was tested against a one-sided alternative according to the Brookmeyer Crowley test. Secondary endpoints included objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS), overall survival (OS), and safety. RESULTS: After a median follow-up of 32.6 months, 140 events were observed in 158 evaluable patients. Median EFS was 8.2 months (90% CI, 5.9-8.9; p = 0.188) in arm A vs 8.3 months (90% CI, 6.2-9.7, p = 0.078) in arm B. Progression-free survival, overall survival, and response rates were similar in both groups. A higher percentage of dose reductions and discontinuations due to adverse events (AEs) was noted in arm B. The most frequently reported non-haematological AEs were fatigue (grade [G] 2-3 toxicity occurrence in arm A vs B, 43% and 51%, respectively) and peripheral neuropathy (G2-3 arm A vs B, 19% and 38%, respectively). CONCLUSION: Pre-specified outcomes were similar in both treatment arms. However, 100 mg/m2 was significantly better tolerated with fewer neurotoxicity-related events, representing a more feasible dose to be recommended for older patients with advanced disease. TRIAL REGISTRATION: EudraCT, 2012-002707-18 . Registered on June 4, 2012. NIH ClinicalTrials.gov, NCT02783222 . Retrospectively registered on May 26, 2016.

Clinical outcomes after palbociclib with or without endocrine therapy in postmenopausal women with hormone receptor positive and HER2-negative metastatic breast cancer enrolled in the TREnd trial.

Currently, there is limited data regarding the effectiveness of standard subsequent line therapies such as endocrine therapy, chemotherapy, or targeted agents after progression on CDK4/6 inhibitor-based regimens. This paper describes time-to-treatment failure beyond progression on palbociclib or palbociclib+endocrine therapy in patients enrolled in the phase II, multicenter TREnd trial. Our results indicate that there is limited benefit from post-palbociclib treatment, regardless of the type of therapy received. A small population of long responders were identified who demonstrated ongoing benefit from a subsequent line of endocrine therapy after progression to palbociclib-based regimens. A translational research program is ongoing on this population of outliers.

A gene expression signature of Retinoblastoma loss-of-function predicts resistance to neoadjuvant chemotherapy in ER-positive/HER2-positive breast cancer patients.

PURPOSE: HER2-positive (HER2+) breast cancers show heterogeneous response to chemotherapy, with the ER-positive (ER+) subgroup deriving less benefit. Loss of retinoblastoma tumor suppressor gene (RB1) function has been suggested as a cardinal feature of breast cancers that are more sensitive to chemotherapy and conversely resistant to CDK4/6 inhibitors. We performed a retrospective analysis exploring RBsig, a gene signature of RB loss, as a potential predictive marker of response to neoadjuvant chemotherapy in ER+/HER2+ breast cancer patients. METHODS: We selected clinical trials of neoadjuvant chemotherapy ± anti-HER2 therapy in HER2+ breast cancer patients with available information on gene expression data, hormone receptor status, and pathological complete response (pCR) rates. RBsig expression was computed in silico and correlated with pCR. RESULTS: Ten studies fulfilled the inclusion criteria and were included in the analysis (514 patients). Overall, of 211 ER+/HER2+ breast cancer patients, 49 achieved pCR (23%). The pCR rate following chemotherapy ± anti-HER2 drugs in patients with RBsig low expression was significantly lower compared to patients with RBsig high expression (16% vs. 30%, respectively; Fisher's exact test p = 0.015). The area under the ROC curve (AUC) was 0.62 (p = 0.005). In the 303 ER-negative (ER-)/HER2+ patients treated with chemotherapy ± anti-HER2 drugs, the pCR rate was 43%. No correlation was found between RBsig expression and pCR rate in this group. CONCLUSIONS: Low expression of RBsig identifies a subset of ER+/HER2+ patients with low pCR rates following neoadjuvant chemotherapy ± anti-HER2 therapy. These patients may potentially be spared chemotherapy in favor of anti-HER2, endocrine therapy, and CDK 4/6 inhibitor combinations.

Using CTCs for pharmacogenomic analysis.

In the era of precision medicine in oncology, pharmacogenomic assessment is a vital step in delivering personalized care. Increasing evidence points towards the importance of assessing molecular features of the advanced disease, rather than relying on the primary tumor sample, in order to appreciate the evolution of the tumor and to target relevant features. Circulating tumor cells (CTCs) represent a novel method of tumor sampling, as they offer a contemporaneous picture of the current disease state without the need for invasive needle biopsy. As they may derive from any number of metastatic sites, the potential to capture the heterogeneity of the disease is increased. Improvements in CTC capture, enrichment and isolation technology now allow sophisticated interrogation of these cells, such that pharmacogenomic assessment of CTCs is now possible, and the clinical potential is being explored. We review current and potential uses for CTCs for pharmacogenomic analysis.

Patterns of Care and Clinical Outcomes of First-Line Trastuzumab-Based Therapy in HER2-Positive Metastatic Breast Cancer Patients Relapsing After (Neo)Adjuvant Trastuzumab: An Italian Multicenter Retrospective Cohort Study.

BACKGROUND: We evaluated the patterns of care and clinical outcomes of metastatic breast cancer patients treated with first-line trastuzumab-based therapy after previous (neo)adjuvant trastuzumab. MATERIALS AND METHODS: A total of 416 consecutive, HER2-positive metastatic breast cancer patients who had received first-line trastuzumab-based therapy were identified at 14 Italian centers. A total of 113 patients had presented with de novo stage IV disease and were analyzed separately. Dichotomous clinical outcomes were analyzed using logistic regression and time-to-event outcomes using Cox proportional hazards models. RESULTS: In the 202 trastuzumab-naïve patients and 101 patients with previous trastuzumab exposure, we observed the following outcomes, respectively: overall response rate, 69.9% versus 61.3% (adjusted odds ratio [OR], 0.62; p = .131), clinical benefit rate, 79.1% versus 72.5% (adjusted OR, 0.73; p = .370), median progression-free survival (PFS), 16.1 months versus 12.0 months (adjusted hazards ratio [HR], 1.33; p = .045), and median overall survival (OS), 52.2 months versus 48.2 months (adjusted HR, 1.18; p = .404). Patients with a trastuzumab-free interval (TFI) <6 months, visceral involvement, and hormone receptor-negative disease showed a worse OS compared with patients with a TFI of ≥6 months (29.5 vs. 48.3 months; p = .331), nonvisceral involvement (48.0 vs. 60.3 months; p = .270), and hormone receptor-positive disease (39.8 vs. 58.6 months; p = .003), respectively. CONCLUSION: Despite the inferior median PFS, trastuzumab-based therapy was an effective first-line treatment for patients relapsing after (neo)adjuvant trastuzumab. Previous trastuzumab exposure and the respective TFI, type of first site of disease relapse, and hormone receptor status should be considered in the choice of the best first-line treatment option for HER2-positive metastatic breast cancer patients.

Mutational Analysis of Circulating Tumor DNA in Patients With Estrogen Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer Receiving Palbociclib: Results From the TREnd Trial.

PURPOSE: To identify prognostic circulating biomarkers to cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i), we performed a mutational analysis on circulating tumor DNA (ctDNA) samples from patients included in the TREnd trial, which randomly assigned patients to receive the CDK4/6i palbociclib alone or with the endocrine treatment (ET) to which they had progressed. METHODS: Forty-six patients were enrolled in this substudy. Plasma was collected before treatment (T0), after the first cycle of therapy (T1), and at the time of progression (T2). ctDNA hybridization and capture were performed using the Illumina TruSight Tumor 170 Kit. Acquired mutations were confirmed by digital polymerase chain reaction. Progression-free survival analysis was estimated using the Kaplan-Meier method and compared with the log-rank test. RESULTS: The most frequently mutated genes at T0 were ESR1 (23%), PIK3CA (17%), AR, FGFR2, and TP53 (10%). Mutations in ESR1 at T0 conferred higher risk of progression in the entire population (P = .02) and in patients treated with palbociclib + ET (P = .04). ESR1 mutation effect remained significant after correction for clinical variables (P = .03). PIK3CA mutations at T0 were not prognostic, but higher risk of progression was observed when a broader analysis of PI3K pathway was performed (P = .04). At T2, we observed the emergence of nine new mutations in seven genes. CONCLUSION: Mutations in ESR1 and in PI3K pathway genes at T0 were associated with worse prognosis in palbociclib-treated patients. We describe the emergence of newly acquired mutations in palbociclib-treated patients, which might potentially affect subsequent treatment.

Multimodality treatment of gynecomastia in patients receiving antiandrogen therapy for prostate cancer in the era of abiraterone acetate and new antiandrogen molecules.

Gynecomastia is a pathological enlargement of male breasts due to hormonal imbalance and elevation of estrogens at the expense of testosterone. It is very important to diagnose this disease precociously because it can be the expression of different underlying pathologies. Besides genetic, chromosomal or chronic diseases, drugs often represent the principal cause of this hormonal disequilibrium. In the elderly population, antiandrogen therapy for prostate cancer frequently induces gynecomastia, thus negatively affecting the patients' compliance to treatment because of physical and psychological discomfort deriving from this condition; gynecomastia can in fact be associated with severe breast pain, and it can modify how patients see their own body. During the past decades and even today, many different surgical, radiotherapeutic or clinical approaches have been proposed to prevent or treat this hypertrophy. This article focuses on gynecomastia associated with antiandrogen-based hormonal treatment and shortly reviews the currently most often used therapeutic options for preventing and treating this pathology.

Risk assessment of disease recurrence in early breast cancer: A serum metabolomic study focused on elderly patients.

BACKGROUND: We previously showed that metabolomics predicts relapse in early breast cancer (eBC) patients, unselected by age. This study aims to identify a "metabolic signature" that differentiates eBC from advanced breast cancer (aBC) patients, and to investigate its potential prognostic role in an elderly population. METHODS: Serum samples from elderly breast cancer (BC) patients enrolled in 3 onco-geriatric trials, were retrospectively analyzed via proton nuclear magnetic resonance (1H NMR) spectroscopy. Three nuclear magnetic resonance (NMR) spectra were acquired for each serum sample: NOESY1D, CPMG, Diffusion-edited. Random Forest (RF) models to predict BC relapse were built on NMR spectra, and resulting RF risk scores were evaluated by Kaplan-Meier curves. RESULTS: Serum samples from 140 eBC patients and 27 aBC were retrieved. In the eBC cohort, median age was 76 years; 77% of patients had luminal, 10% HER2-positive and 13% triple negative (TN) BC. Forty-two percent of patients had tumors >2 cm, 43% had positive axillary nodes. Using NOESY1D spectra, the RF classifier discriminated free-from-recurrence eBC from aBC with sensitivity, specificity and accuracy of 81%, 67% and 70% respectively. We tested the NOESY1D spectra of each eBC patient on the RF models already calculated. We found that patients classified as "high risk" had higher risk of disease recurrence (hazard ratio (HR) 3.42, 95% confidence interval (CI) 1.58-7.37) than patients at low-risk. CONCLUSIONS: This analysis suggests that a "metabolic signature", identified employing NMR fingerprinting, is able to predict the risk of disease recurrence in elderly patients with eBC independently from standard clinicopathological features.

Adjuvant capecitabine in triple negative breast cancer patients with residual disease after neoadjuvant treatment: real-world evidence from CaRe, a multicentric, observational study.

Background: In triple negative breast cancer patients treated with neoadjuvant chemotherapy, residual disease at surgery is the most relevant unfavorable prognostic factor. Current guidelines consider the use of adjuvant capecitabine, based on the results of the randomized CREATE-X study, carried out in Asian patients and including a small subset of triple negative tumors. Thus far, evidence on Caucasian patients is limited, and no real-world data are available. Methods: We carried out a multicenter, observational study, involving 44 oncologic centres. Triple negative breast cancer patients with residual disease, treated with adjuvant capecitabine from January 2017 through June 2021, were recruited. We primarily focused on treatment tolerability, with toxicity being reported as potential cause of treatment discontinuation. Secondarily, we assessed effectiveness in the overall study population and in a subset having a minimum follow-up of 2 years. Results: Overall, 270 patients were retrospectively identified. The 50.4% of the patients had residual node positive disease, 7.8% and 81.9% had large or G3 residual tumor, respectively, and 80.4% a Ki-67 >20%. Toxicity-related treatment discontinuation was observed only in 10.4% of the patients. In the whole population, at a median follow-up of 15 months, 2-year disease-free survival was 62%, 2 and 3-year overall survival 84.0% and 76.2%, respectively. In 129 patients with a median follow-up of 25 months, 2-year disease-free survival was 43.4%, 2 and 3-year overall survival 78.0% and 70.8%, respectively. Six or more cycles of capecitabine were associated with more favourable outcomes compared with less than six cycles. Conclusion: The CaRe study shows an unexpectedly good tolerance of adjuvant capecitabine in a real-world setting, although effectiveness appears to be lower than that observed in the CREATE-X study. Methodological differences between the two studies impose significant limits to comparability concerning effectiveness, and strongly invite further research.

PIK3CA co-occurring mutations and copy-number gain in hormone receptor positive and HER2 negative breast cancer.

We aim to elucidate the prognostic value of PIK3CA mutations and copy number (CN) gain (PIK3CA-mut/gain) in hormone receptor-positive and HER2-negative (HR + /HER2-) breast cancer (BC). We analyzed primary HR + /HER2- BC from three publicly available datasets comprising over 2000 samples and assessed the associations with tumoral and clinical characteristics and outcome. Clinical benefit (CB) in alpelisib-treated patients from two studies including 46 patients was analyzed. About 8-10% of HR + /HER2- primary BC had PIK3CA-mut/gain. In two of the datasets analyzed, among patients with PIK3CA mutant tumors, those with mut/gain had significantly worse outcome compared to those with CN neutral (PIK3CA-mut/neut) and PIK3CA-mut/gain remained an independent prognostic factor. CB of alpelisib-treated patients with PIK3CA-mut/gain and PIK3CA-mut/neut tumors was comparable. PIK3CA CN might help clarifying the prognostic and predictive role of PIK3CA mutations. Further studies are warranted.

PANHER study: a 20-year treatment outcome analysis from a multicentre observational study of HER2-positive advanced breast cancer patients from the real-world setting.

BACKGROUND: The evolution of therapeutic landscape of human epidermal growth factor receptor-2 (HER2)-positive breast cancer (BC) has led to an unprecedented outcome improvement, even if the optimal sequence strategy is still debated. To address this issue and to provide a picture of the advancement of anti-HER2 treatments, we performed a large, multicenter, retrospective study of HER2-positive BC patients. METHODS: The observational PANHER study included 1,328 HER2-positive advanced BC patients treated with HER2 blocking agents since June 2000 throughout July 2020. Endpoints of efficacy were progression-free survival (PFS) and overall survival (OS). RESULTS: Patients who received a first-line pertuzumab-based regimen showed better PFS (p < 0.0001) and OS (p = 0.004) than those receiving other treatments. Median PFS and mOS from second-line starting were 8 and 28 months, without significant differences among various regimens. Pertuzumab-pretreated patients showed a mPFS and a mOS from second-line starting not significantly affected by type of second line, that is, T-DM1 or lapatinib/capecitabine (p = 0.80 and p = 0.45, respectively). Conversely, pertuzumab-naïve patients receiving second-line T-DM1 showed a significantly higher mPFS compared with that of patients treated with lapatinib/capecitabine (p = 0.004). Median OS from metastatic disease diagnosis was higher in patients treated with trastuzumab-based first line followed by second-line T-DM1 in comparison to pertuzumab-based first-line and second-line T-DM1 (p = 0.003), although these data might be partially influenced by more favorable prognostic characteristics of patients in the pre-pertuzumab era. No significant differences emerged when comparing patients treated with 'old' or 'new' drugs (p = 0.43), even though differences in the length of the follow-up between the two cohorts should be taken into account. CONCLUSION: Our results confirmed a relevant impact of first-line pertuzumab-based treatment and showed lower efficacy of second-line T-DM1 in trastuzumab/pertuzumab pretreated, as compared with pertuzumab-naïve patients. Our findings may help delineate a more appropriate therapeutic strategy in HER2-positive metastatic BC. Prospective randomized trials addressing this topic are awaited.

Plasma Thymidine Kinase Activity as a Biomarker in Patients with Luminal Metastatic Breast Cancer Treated with Palbociclib within the TREnd Trial.

PURPOSE: Thymidine kinase 1 (TK1) is downstream to the CDK4/6 pathway, and TK activity (TKa) measured in blood is a dynamic marker of outcome in patients with advanced breast cancer (ABC). This study explores TK1 as a biomarker of palbociclib response, both in vitro and in patients with ABC. EXPERIMENTAL DESIGN: Modulation of TK1 levels and activity by palbociclib were studied in seven estrogen receptor-positive breast cancer cell lines: sensitive (PDS) and with palbociclib acquired resistance (PDR). TKa was assayed in plasma obtained at baseline (T0), after one cycle (T1), and at disease progression on palbociclib (T2) in patients enrolled in the "To Reverse ENDocrine Resistance" (TREnd) trial (n = 46). RESULTS: Among E2F-dependent genes, TK1 was significantly downregulated after short-term palbociclib. Early TKa reduction by palbociclib occurred in PDS but not in PDR cells. In patients, median TKa (mTKa) at T0 was 75 DiviTum units per liter (Du/L), with baseline TKa not proving prognostic. At T1, mTKa decreased to 35 Du/L, with a minority of patients (n = 8) showing an increase-correlating with a worse outcome than those with decreased/stable TKa (n = 33; mPFS 3.0 vs 9.0 months; P = 0.002). At T2, mTKa was 251 Du/L; patients with TKa above the median had worse outcomes on post-study treatment compared with those with lower TKa (2.9 vs 8.7 months; P = 0.05). CONCLUSIONS: TK is a dynamic marker of resistance to palbociclib which may lead to early identification of patients in whom treatment escalation may be feasible. In addition, TKa may stratify prognosis in patients with acquired resistance to palbociclib.

Metabolomic analysis of serum may refine 21-gene expression assay risk recurrence stratification.

Despite recent refinements to the 21-gene g score, allowing a better identification of patients who may derive no benefit from the addition of adjuvant chemotherapy to that of endocrine therapy, patients with early breast cancer still stand to be over-treated in the setting of clinical and/or genomic uncertainty or discordance. Here we describe and demonstrate a potential approach of further refining the OncotypeDX risk score by metabolomic analysis of serum. In a clinical dataset (N = 87), the risk of recurrence was further sub-stratified by metabolomic signature, with an effective splitting of each Oncotype risk classification. A total of seven recurrences were recorded, with metabolomic analysis accurately predicting six of these. Contrastingly, the genomic risk score of the seven recurrences ranged across all three Oncotype classifications (one recurrence occurred in the "low"-risk group, three in the "intermediate" group and three in the "high"-risk group).

Cyclin-Dependent Kinase 4/6 Inhibitors in Neoadjuvant Endocrine Therapy of Hormone Receptor-Positive Breast Cancer.

The landscape of therapeutic options for the treatment of hormone receptor (HR)-positive (HR+) HER2- breast cancer (BC) has been profoundly changed by the introduction of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors into the metastatic setting. Currently all CDK4/6 inhibitors are approved only in the metastatic setting by Food and Drug Administration (FDA) and European Medicine Agency (EMA), whereas their role in the neoadjuvant setting is still at an investigational stage. Exploitation of novel agents such as CDK4/6 inhibitors to improve the efficacy of neoadjuvant endocrine therapy (ET) or to overcome de novo resistance to ET is an area of research under active evaluation. We present a review of the currently available data and ongoing clinical trials that are evaluating the role of CDK4/6 inhibitors in neoadjuvant therapy of HR+ HER2- early BC, and also illustrate translational aspects, such as the potential biomarkers of response to these new therapeutic agents.

The optimal duration of adjuvant endocrine therapy in early luminal breast cancer: A concise review.

Patients with luminal early breast cancer are at risk of relapse, even after five years of adjuvant endocrine therapy. To date, no biomarkers have been clinically validated to identify those patients at risk of late recurrence, who might benefit from extended adjuvant endocrine therapy. In recent decades, multiple clinical trials have tested the role of extending adjuvant endocrine therapies in patients with luminal disease. However, the data currently at our disposal are conflicting. This article reviews all the major trials concerning extended adjuvant endocrine regimens, and formulates some general conclusions and hypotheses of future study.

Mechanisms of Resistance to CDK4/6 Inhibitors: Potential Implications and Biomarkers for Clinical Practice.

The recent arrival of CDK4/6 inhibitor agents, with an approximate doubling of progression-free survival (PFS) associated with their use in hormone receptor-positive, HER2-negative advanced breast cancer (BC), has radically changed the approach to managing this disease. However, resistance to CDK4/6 inhibitors is considered a near-inevitability in most patients. Mechanisms of resistance to these agents are multifactorial, and research in this field is still evolving. Biomarkers with the ability to identify early resistance, or to predict the likelihood of successful treatment using CDK4/6 inhibitors are yet to be identified, and represent an area of unmet clinical need. Here we present selected mechanisms of resistance to CDK4/6 inhibitors, largely focussing on roles of Rb, cyclin E1, and the PIK3CA pathway, with discussion of associated biomarkers which have been investigated and applied in recent pre-clinical and clinical studies. These biological drivers may furthermore influence clinical treatment strategies adopted beyond CDK4/6 resistance.

An RB-1 loss of function gene signature as a tool to predict response to neoadjuvant chemotherapy plus anti-HER2 agents: a substudy of the NeoALTTO trial (BIG 1-06).

BACKGROUND: Chemotherapy added to anti-HER2 agents (H) is the treatment of choice in patients with HER2+ early breast cancer. However, HER2+ tumours are clinically and biologically heterogeneous, and treatment response varies significantly by hormone receptor (HR) status and molecular subtype. Predictive biomarkers are needed in this context. This study assessed whether an RB-1 loss of function gene signature (RBsig) is predictive of response to neoadjuvant chemotherapy in combination with trastuzumab, lapatinib or both, within the NeoALTTO trial. METHODS: We collected RNA-sequencing data from pretreatment biopsies derived from the NeoALTTO trial. RBsig expression was computed retrospectively and correlated with pathological complete response (pCR) using receiver-operating characteristic (ROC) curves. The RBsig was dichotomised as High/Low in correspondence to the 25th percentile. Reported p values resulted from Fisher's exact test. RESULTS: Of 455 NeoALTTO patients, 244 were eligible for this substudy (HR+ n = 129; HR- n = 115). Overall, pCR rate was significantly higher in patients with RBsig High tumours than those with RBsig Low (35% versus 18% respectively; p = 0.01). The area under the ROC curve (AUC) was 0.60 (95% CI 0.52-0.67). A remarkably low pCR rate of 11% was seen in HR+/RBsig Low patients versus 28% in HR+/RBsig High. CONCLUSIONS: These results indicate RBsig may add valuable information to HER2 and HR expression, which may in turn inform treatment choices. HR+/HER2+/RBsig Low breast cancers exhibited the poorest pathological response following chemotherapy plus H. Accordingly, in such patients, endocrine therapy in combination with H and, possibly, a CDK4/6 inhibitor, may potentially prove to be a more effective treatment.