CDK4/6 inhibitors in advanced hormone receptor-positive/HER2-negative breast cancer: a systematic review and meta-analysis of randomized trials

Efficacy and Safety of Abemaciclib in Combination With Endocrine Therapy for HR+/HER2- Advanced or Metastatic Breast Cancer: A Systematic Review and Meta-Analysis

OBJECTIVES

Breast cancer, particularly the hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) subtype, remains a major global health concern. Abemaciclib, a CDK4/6 inhibitor, has shown promising results in treating advanced cases. This study comprehensively assesses the efficacy and safety of abemaciclib in combination with endocrine therapy for HR+/HER2- advanced or metastatic breast cancer.

METHODS

Following PRISMA guidelines, a systematic review and meta-analysis was conducted. A thorough literature search was conducted on PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov til December 2023. Inclusion criteria encompassed randomized controlled trials and retrospective cohort studies reporting on abemaciclib in approved doses, either as monotherapy or in combination. Outcome assessments included progression-free survival (PFS), overall response rate (ORR), side effects/adverse effects (SE/AE), and overall survival (OS). Quality assessment utilized Cochrane's revised risk of bias tool and Newcastle-Ottawa scale.

RESULTS

Pooled results of 22 studies involving 14,010 patients revealed that abemaciclib significantly improved PFS (hazard ratio=0.53; 95% CI: 0.48-0.59; P=0.00; I2=0%), ORR (risk ratio=2.31; 95% CI: 1.93-2.75; P=0.00; I2=0%), and OS (risk ratio=0.76 (95% CI: 0.65-0.87; P=0.001; I2=0%). However, abemaciclib increased the risk of adverse events in the fulvestrant and nonsteroidal aromatase inhibitor (NSAI) combinations, respectively.

CONCLUSIONS

Abemaciclib, particularly in combination with fulvestrant, emerges as an effective therapeutic option for HR+/HER2- advanced or metastatic breast cancer, improving PFS and OS. The higher toxicity profile warrants cautious use, especially in treatment-naive patients.

Confirming the efficacy and safety of CDK4/6 inhibitors in the first-line treatment of HR+ advanced breast cancer: a systematic review and meta-analysis

Objective: Cyclin-dependent kinase (CDK) 4 and 6 inhibitors (abemaciclib, palbociclib and ribociclib) have been recommended in the first-line treatment of hormone receptor-positive (HR+) breast cancer in China. Our study aims to evaluate the efficacy and safety of CDK4/6 inhibitors by processing survival data using fractional polynomial modeling methods. Methods: Phase II or III randomized controlled trials in treatment-naive HR + patients with advanced breast cancer were systematically searched through the preset search strategy. The fractional polynomial (FP) model was used to relax the proportional hazard assumption and obtain time-varying hazard ratio (HR). Progression-free life years (PFLYs) and life years (LYs) were calculated from the area under curve (AUC) of the predicted progression-free survival (PFS) and overall survival (OS) curves to evaluate the long-term efficacy benefit. Odds ratio (OR) of grade≥3 adverse events were analyzed for safety outcomes. Results: 6 randomized controlled trials with 2,638 patients were included. The first-order FP model (p = -1) and the first-order FP model (p = 1) were used to calculate the time-varying HR of PFS and OS, respectively. Extrapolating to 240 months, abemaciclib obtained a PFS benefit of 3.059 PFLYs and 6.275 LYs by calculating the AUC of the PFS and OS curves. Palbociclib obtained 2.302 PFLYs and 6.351 LYs. Ribociclib obtained 2.636 PFLYs and 6.543 LYs. In terms of safety, the use of CDK4/6 inhibitors resulted in a higher risk of adverse events (OR = 9.84, 95% CI: 8.13-11.95), especially for palbociclib (OR = 14.04, 95% CI: 10.52-18.90). Conclusion: The use of CDK4/6 inhibitors in treatment-naive patients with HR + advanced breast cancer significantly improves survival, but also increases the risk of adverse events. Abemaciclib and ribociclib may be the best options for prolonging PFS and OS in treatment-naïve patients, respectively.

Efficacy of CDK4/6 inhibitors combined with endocrine therapy in HR+/HER2- breast cancer: an umbrella review

BACKGROUND

The use of Cyclin-Dependent kinase 4 and 6 (CDK4/6) inhibitors has profoundly changed the challenge of endocrine therapy (ET) resistance in hormone receptor-positive (HR+)/HER2-negative (HER2-) breast cancer. However, there is currently no comprehensive evaluation of the evidence for the efficacy of CDK4/6 inhibitors. We conducted an umbrella review to explore the impact of CDK4/6 inhibitor combined with ET on breast cancer by summarizing and assessing the meta-analysis (MA) and systematic review (SR) evidence.

METHODS

Cochrane, PubMed, Embase, and Web of Science databases were searched from inception to August 1st, 2022. Eligible studies were assessed for methodological quality, report quality, and evidence quality using the AMSTAR-2 scale, PRISMA 2020, and GRADE grading systems, respectively. We summarized all efficacy outcomes of CDK4/6 inhibitors for breast cancer and reported them in narrative form.

RESULTS

Our study included 24 MAs and SRs. The strongest evidence demonstrated that CDK4/6 inhibitor combined with ET significantly improved progression-free survival (PFS), overall survival (OS) in advanced breast cancer (ABC). A large body of moderate to high evidence showed a significant association between combination therapy and objective response rate (ORR), and clinical benefit response (CBR) benefit in ABC. Low evidence suggested some degree of benefit from combination therapy in second progression-free survival (PFS2) and time to subsequent chemotherapy (TTC) outcomes in ABC and invasive disease-free survival (IDFS) outcomes in early breast cancer.

CONCLUSIONS

Based on current evidence, CDK4/6 inhibitors combined with ET have great confidence in improving PFS, OS, ORR, and CBR outcomes in patients with ABC, which provides more rational and valid evidence-based medicine for CDK4/6 inhibitor promotion and clinical decision support.

The adverse events of CDK4/6 inhibitors for HR+/ HER2- breast cancer: an umbrella review of meta-analyses of randomized controlled trials

Background: The clinical selection of three CDK4/6 inhibitors presents a challenging issue, owing to the absence of distinct clinical case characteristics, biomarkers, and their comparable clinical benefits in progression-free survival and overall survival To inform clinical treatment decisions, we conducted a comprehensive evaluation of the adverse events associated with CDK4/6 inhibitors in combination with endocrine therapy for hazard ratio+/HER2-breast cancer. Methods: We searched Cochrane, PubMed, Embase, and Web of Science databases from their inception until 1 August 2022. The results were summarized narratively, and we assessed the methodological quality, reporting quality, and evidence quality of AEs by AMSTAR-2, PRISMA, and GRADE. Results: Our analysis included 24 meta-analyses systematic reviews that evaluated the quality of AEs in 13 cases of early breast cancer (EBC) and 158 cases of advanced breast cancer The addition of CDK4/6 inhibitors was found to significantly increase AEs of any grade and AEs of grade 3 or higher in early breast cancer, along with a significant increase in the risk of treatment discontinuation. In advanced breast cancer, high and moderate-quality evidence indicated that CDK4/6 inhibitors significantly increased AEs across all grades, including grade 3/4 AEs, leucopenia, grade 3/4 leucopenia, neutropenia, grade 3/4 neutropenia, anemia, grade 3/4 anemia, nausea, grade 3/4 constipation, fatigue, pyrexia, venous thromboembolism abdominal pain, and cough. However, they did not significantly elevate the incidence of grade 3/4 diarrhea. Subgroup analysis revealed that palbociclib primarily increased hematologic toxicity, particularly grade 3/4 neutropenia, anemia, and thrombocytopenia. Ribociclib was mainly associated with grade 3/4 neutropenia, prolonged QT interval, and alopecia. Abemaciclib was closely linked with diarrhea and elevated blood creatinine levels. Conclusion: The AEs associated with CDK4/6 inhibitors vary, necessitating individualized and precise clinical selection for optimal management. This approach should be based on the patient's medical history and the distinct characteristics of different CDK4/6 inhibitors to improve the patient's quality of life. Systematic Review Registration: [https://systematicreview.gov/], identifier [CRD42022350167].

Retrospective cohort study of CDK4/6-inhibitor-induced alopecia in breast cancer patients

PURPOSE

Dermatologic adverse events commonly result in the interruption of oncologic treatment, and targeted therapies are the most frequently interrupted class of anticancer agents. Alopecia is a common cutaneous adverse event reported with CK4/6i therapy. Though the clinical characteristics and therapeutic response of EIA have been well documented, few studies have characterized alopecia in patients treated with CDK4/6i.

METHODS

This study analyzed a retrospective cohort of 28 breast cancer patients diagnosed with endocrine-induced alopecia (EIA) or CDKiA. Comparative analysis of the clinical characteristics of alopecia and therapeutic response to minoxidil was conducted. Therapeutic response to minoxidil (LDOM or topical [5%] solution or foam) was assessed by both Dean Scale and qualitative clinical improvement by comparison of pretreatment and posttreatment clinical images by single-blinded, board-certified academic dermatologists (ST and BD).

RESULTS

CDKiA was clinically similar to androgenetic alopecia and specific vertex involvement was more common in patients treated with CDK4/6i + ET than endocrine monotherapy (n = 7 [70.0%] vs n = 4 [36.4%]; p = 0.04), respectively. After 4-6 months of minoxidil, there was a moderate to significant qualitative alopecia improvement in 80% of CDKiA patients versus 94.4% of EIA patients. Additionally, superior improvement of mean Dean Score grade was observed in EIA (with change from pre- to posttreatment - 0.44; p = 0.0002).

CONCLUSION

Compared to endocrine monotherapy, patients on combination CDK4/6i + ET had greater extent of vertex involvement and were more recalcitrant to minoxidil. The preferential vertex involvement observed in CDKiA suggests that combination therapy with minoxidil and topical antiandrogens with poor systemic absorption should be studied in this setting.

Observational study of HR+/HER2- metastatic breast cancer patients treated with abemaciclib in Spain in the Named Patient Use Program (AbemusS)

INTRODUCTION/OBJECTIVES

To describe abemaciclib use in patients with hormone receptor-positive, human epidermal growth factor receptor-negative (HR+/HER2-) metastatic breast cancer (mBC) who participated in the Named Patient Use program (NPU) in Spain.

MATERIAL AND METHODS

This retrospective study was based on medical record review of patients across 20 centers during 2018/2019. Patients were followed up until death, enrolment in a clinical trial, loss of follow-up or study end. Clinical and demographic characteristics, treatment patterns and abemaciclib effectiveness were analyzed; time-to-event and median times were estimated using the Kaplan-Meier (KM) method.

RESULTS

The study included 69 female patients with mBC (mean age 60.4 ± 12.4 years), 86% of whom had an initial diagnosis of early BC and 20% had an ECOG ≥ 2. Median follow-up was 23 months (range 16-28). Metastases were frequently observed in bone (79%) and visceral tissue (65%), with 47% having metastases in > 2 sites. Median number of treatment lines before abemaciclib was 6 (range 1-10). Abemaciclib monotherapy was received by 72% of patients and combination therapy with endocrine therapy by 28% of patients; 54% of patients required dose adjustments, with a median time to first adjustment of 1.8 months. Abemaciclib was discontinued in 86% of patients after a median of 7.7 months (13.2 months for combination therapy and 7.0 months for monotherapy) mainly due to disease progression (69%).

CONCLUSION

These results suggest that abemaciclib is effective, as monotherapy and in combination, for patients with heavily pretreated mBC, consistent with clinical trial results.

Efficacy and safety of cyclin-dependent kinase 4/6 inhibitor in patients with advanced breast cancer: A real-world experience

BACKGROUND

Cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) have been shown to improve progression-free survival (PFS) in patients with metastatic breast cancer (MBC) in randomized control trials. This study aimed to evaluate the efficacy and safety of CDK4/6i in patients with advanced breast cancer (ABC) in a clinical setting.

METHODS

Consecutive patients with ABC were treated between October 2019 and March 2023 at Taipei Tzu Chi Hospital, Taiwan. Patients who had received at least one dose of CDK4/6i were included in this retrospective study. The main outcome of this study was efficacy based on the treating physicians' assessments in terms of PFS, and overall survival (OS), as well as the factors associated with patient outcome. The secondary outcome was safety.

RESULTS

A total of 85 patients were included in the analysis, with a mean age of 66.8 years. After a median follow-up of 16.1 months, the median PFS was 28.4 months (95% CI: 22.5-33.6) and the median OS could not yet be estimated. The most common adverse events (AE) were fatigue (50.8%), anorexia (45.9%), and leukopenia (44.7%). In multivariable analysis, treatment with CDK4/6i with any grade AE or response to treatment effect (CR/PR) was an independent predictor for longer PFS (hazard ratio [HR] = 0.27, 95% CI: 0.11-0.68; HR = 0.21, 95% CI: 0.06-0.67; p < 0.05).

CONCLUSION

CDK4/6i administered in a real-world setting exhibits a similar survival benefit with the clinical trials.

Treatment of De-Differentiated Liposarcoma in the Era of Immunotherapy

Well-differentiated/de-differentiated liposarcoma (WDLPS/DDLPS) is one of the most common histologic subtypes of soft tissue sarcoma (STS); however, treatment options remain limited. WDLPS and DDLPS both exhibit the characteristic amplification of chromosome region 12q13-15, which contains the genes CDK4 and MDM2. DDLPS exhibits higher amplification ratios of these two and carries additional genomic lesions, including the amplification of chromosome region 1p32 and chromosome region 6q23, which may explain the more aggressive biology of DDLPS. WDLPS does not respond to systemic chemotherapy and is primarily managed with local therapy, including multiple resections and debulking procedures whenever clinically feasible. In contrast, DDLPS can respond to chemotherapy drugs and drug combinations, including doxorubicin (or doxorubicin in combination with ifosfamide), gemcitabine (or gemcitabine in combination with docetaxel), trabectedin, eribulin, and pazopanib. However, the response rate is generally low, and the response duration is usually short. This review highlights the clinical trials with developmental therapeutics that have been completed or are ongoing, including CDK4/6 inhibitors, MDM2 inhibitors, and immune checkpoint inhibitors. This review will also discuss the current landscape in assessing biomarkers for identifying tumors sensitive to immune checkpoint inhibitors.

Research Status of Systemic Adjuvant Therapy for Early Breast Cancer

Breast cancer has surpassed lung cancer as the most common cause of cancer deaths, worldwide. Early breast cancers are treatment sensitive and patients under standardized treatment have prolonged. Breast cancer treatment has significantly evolved from the conventional surgical approach and radiotherapy to local and systemic adjuvant therapies. Though localized breast cancers are clinically manageable, distant recurrence is a cause of morbid concern. Adjuvant systemic therapy is effective in both distant and local recurrences and hence gained significant attention. Early breast cancer prognosis has greatly improved in the past 3 decades with reduced mortality rates due to the widespread use of adjuvant therapy. It can markedly increase the cure rate of breast cancers, and postoperative adjuvant therapy became a part of comprehensive breast cancer treatment. Further research to understand the early breast cancer characteristics could expand the treatment modalities that can improve the outcomes and survival benefits of breast cancer patients.

Endocrine Therapy-Based Strategies for Metastatic Breast Cancer with Different Endocrine Sensitivity Statuses: A Systematic Review and Network Meta-Analysis

BACKGROUND

Novel endocrine therapies (ETs) and targeted therapeutic regimens have been developed to dramatically improve the outcome of hormone receptor-positive (HR+)/HER2-negative (HER2-) metastatic breast cancer (mBC).

METHODS

We performed a systematic search with a predefined search strategy in PubMed, Embase and Cochrane CENTRAL databases to perform a network meta-analysis and evaluate the relative efficacies of ET-based treatment regimens in HR+/HER2- mBC patients with different endocrine sensitivity statuses. The study was registered in the PROSPERO database (CRD42021235570).

RESULTS

A total of 47 trials (20,267 patients) were included. Analysis of progression-free survival (PFS) in endocrine therapy-sensitive (ETS) patients revealed cyclin-dependent kinases 4/6 inhibitors (CDK4/6i) + fulvestrant 500 mg (Ful 500) (random effect (RE): hazard ratio (HR), 0.46; 95% credibility interval (CrI), 0.27-0.78; surface under the cumulative ranking curve (SUCRA), 0.93; fixed effect (FE): HR, 0.48; 95% CrI, 0.40-0.58; SUCRA, 0.99) to be the best therapy followed by CDK4/6i + aromatase inhibitors (AIs) (RE: HR, 0.53; 95% CrI, 0.40-0.72; SUCRA, 0.86; FE: HR, 0.54; 95% CrI, 0.48-0.61; SUCRA, 0.91). Chemotherapy followed by CDK4/6i + Ful 500 appears to be the most effective option for the endocrine therapy-resistant (ETR) group. Analysis of overall survival revealed CDK4/6i + Ful 500 (SUCRA: 0.99) and AKTi + Ful 500 (SUCRA: 0.87) to be the first-rank regimen for the ETS group and ETR groups, respectively.

CONCLUSION

Our comprehensive analysis suggests that CDK4/6i combined with ETs may be the best treatment option in terms of PFS for ETS patients and chemotherapy for ETR patients with HR+/HER2- mBC. Different endocrine sensitivity statuses required various optimal treatment strategies, which may provide guidance for clinical practice.

Brazilian breast cancer patient-reported outcomes: What really matters for these women

Introduction

Patient-Reported Outcomes (PRO) are directly reported by the patient without interpretation of the patient's response by a clinician or anyone else and pertains to the patient's health, quality of life, or functional status associated with health care or treatment. It can provide patients’ perspectives regarding treatment benefit and harm beyond survival and are often the outcomes of most importance to patients. This study aims to describe and analyze outcomes reported by Brazilian women diagnosed with breast cancer and rank the most important attributes for these patients.

Methods

Observational descriptive study composed of exploratory interviews followed by online questionnaires applied to a convenience sample of women diagnosed with breast cancer.

Results

Twelve women were interviewed to explore the main outcomes and preferences about their treatments, such as the most common side effects and the most impacted aspects of life after diagnosis and BC treatment. Psychological, emotional, and sexual impacts were frequently described as impacted aspects. Fifty-three women, from all the five Brazilian regions, answered the online questionnaire. Following an order of importance ranking, the following outcomes were chosen, respectively: overall survival, progression-free survival; and quality of life. The treatment effects that were considered less important, among this sample, were pain and adverse events.

Conclusions

Thinking about expanding the therapeutic quality of users, it is essential to take into account the experiences of patients. PRO is a trend in current research to achieve this goal, in order to influence the decisions of HTA agencies about the importance of valuing outcomes that affect patients' lives.

Infectious complications of cyclin-dependent kinases 4 and 6 inhibitors in patients with hormone-receptor-positive metastatic breast cancer: a systematic review and meta-analysis

AIM

The combination of cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors plus endocrine therapy (ET) improved the survival outcomes and became the standard of care in the treatment of metastatic hormone-positive breast cancer. However, these combinations increased the risk of neutropenia compared with ET alone. While the infection-related mortalities did not seem to be increased, the exact risk of infections with CDK 4/6 inhibitor and ET combinations is relatively understudied. Therefore, we performed a meta-analysis of CDK 4/6 inhibitor clinical trials to assess the infection risk of adding CDK4/6 inhibitors to ET.

MATERIAL AND METHOD

We systemically searched the PubMed database for relevant clinical trials. For each study, all grade and grade 3 or higher infections, upper respiratory tract infections (URTI), urinary tract infections (UTI), pneumonia, and febrile neutropenia rates were recorded whenever available. The hazard ratios (HR) with a 95% confidence interval (CI) of infection risk were calculated via the generic inverse-variance method with a random-effects model.

RESULTS

Nine eligible studies were included in the analyses (MONALEESA-2,3,7, MONARCH-2,3, MONARCH plus, PALOMA-1,2,3). In the meta-analysis of these studies, CDK 4/6 inhibitors plus ET arms were associated with increased all grade infections (HR 1.77, 95% CI 1.56-2.01, p < 0.00001), grade 3 or higher infections, (HR 1.77, 95% CI 1.28-2.43, p = 0.0005), UTIs (HR 1.59, 95% CI 1.19-2.12, p = 0.002), and febrile neutropenia (HR 4.28, 95% CI 1.73-10.62, p = 0.002).

CONCLUSION

In this meta-analysis, we observed that adding CDK4/6 inhibitors to ET significantly increased the risk of all grade, grade 3 or higher infections, and urinary tract infections. We propose that closer follow-up for infections should be considered for metastatic breast cancer patients using CDK 4/6 inhibitors. This may help clinicians to recognize infections earlier which prevents early death from infection.

Therapeutic potential of CDK4/6 inhibitors in renal cell carcinoma

The treatment of advanced and metastatic kidney cancer has entered a golden era with the addition of more therapeutic options, improved survival and new targeted therapies. Tyrosine kinase inhibitors, mammalian target of rapamycin (mTOR) inhibitors and immune checkpoint blockade have all been shown to be promising strategies in the treatment of renal cell carcinoma (RCC). However, little is known about the best therapeutic approach for individual patients with RCC and how to combat therapeutic resistance. Cancers, including RCC, rely on sustained replicative potential. The cyclin-dependent kinases CDK4 and CDK6 are involved in cell-cycle regulation with additional roles in metabolism, immunogenicity and antitumour immune response. Inhibitors of CDK4 and CDK6 are now commonly used as approved and investigative treatments in breast cancer, as well as several other tumours. Furthermore, CDK4/6 inhibitors have been shown to work synergistically with other kinase inhibitors, including mTOR inhibitors, as well as with immune checkpoint inhibitors in preclinical cancer models. The effect of CDK4/6 inhibitors in kidney cancer is relatively understudied compared with other cancers, but the preclinical studies available are promising. Collectively, growing evidence suggests that targeting CDK4 and CDK6 in kidney cancer, alone and in combination with current therapeutics including mTOR and immune checkpoint inhibitors, might have therapeutic benefit and should be further explored.

Cyclin-dependent kinase 4 and 6 inhibitors in combination with neoadjuvant endocrine therapy in estrogen receptor-positive early breast cancer: a systematic review and meta-analysis

The combination of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors and endocrine treatment has benefited patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER + /HER2-) metastatic breast cancer; however, its effects in the neoadjuvant setting for ER + /HER2- early breast cancer (EBC) are unclear. Systematic searches were performed in PubMed, Embase, Cochrane Library, and major oncological meetings for trials of CDK4/6 inhibitors plus neoadjuvant endocrine treatment (NET) vs. NET/neoadjuvant chemotherapy (NACT) alone up to January 30, 2021. We assessed the efficacy of CDK4/6 inhibitors plus NET vs. NET/NACT alone in ER + /HER2- EBC. Six studies that included 803 patients treated with CDK4/6 inhibitors plus NET vs. NET/NACT alone were used. Compared with NET/NACT alone, CDK4/6 inhibitors plus NET increased the complete cell cycle arrest (CCCA) rate (OR, 9.00; 95% CI, 5.42-14.96; P < 0.001). Nonsignificant differences between CDK4/6 inhibitors and NET/NACT alone occurred in the preoperative endocrine prognostic index (PEPI)-0 rate (OR, 1.13; 95% CI, 0.59-2.18; P = 0.71), pathological complete response (pCR) rate (OR, 0.75; 95% CI, 0.13-4.29; P = 0.74), objective response rate (ORR) (OR, 0.70; 95% CI, 0.21-2.29; P = 0.55), and disease control rate (DCR) (OR, 1.16; 95% CI, 0.47-2.89; P = 0.74). CDK4/6 inhibitors plus NET indicated a high risk of neutropenia (OR, 56.43; 95% CI, 15.76-202.11; P < 0.001) as an adverse effect (AE) and elevated alanine aminotransferase (ALT) level (OR, 15.30; 95% CI, 2.02-115.98; P = 0.008) as grade 3/4 AEs. Compared with NET/NACT alone, CDK4/6 inhibitors plus NET increased CCCA rate in ER + /HER2- EBC patients. CDK4/6 inhibitors plus NET did not substantially improve the PEPI-0 rate, pCR rate, ORR, or DCR. The combination increased the risk of neutropenia and elevated ALT levels. In the neoadjuvant setting, addition of CDK4/6 inhibitors to NET may be an option for treating ER + /HER2- EBC.

Expanding the Clinical Use of CDK4/6 Inhibitors in the Treatment of Hormone Receptor-Positive, HER2-Negative Breast Cancer from Metastatic Setting to Adjuvant Setting

More than two-thirds of patients with breast cancer present with hormone receptor (HR)-positive, human epidermal growth factor receptor-2 (HER2)-negative disease at their initial diagnosis. HR-positive breast cancer’s growth depends on Cyclin D1, a direct transcriptional target of estrogen receptors (ER). The recent introduction of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors (palbociclib, ribociclib, and abemaciclib) has revolutionized the treatment of metastatic HR-positive, HER2-negative breast cancer in both endocrine-sensitive and endocrine-resistant settings and in both pre-and post-menopausal women. Multiple large randomized clinical trials had demonstrated improvement in progression-free survival (PFS) and, more recently, in overall survival (OS). Adjuvant endocrine therapy (ET) significantly reduces the risk of recurrence and death among patients with HR-positive early-stage breast cancer (EBC). However, up to 20% of these patients will experience local, regional or distal recurrences in the first ten years. Such resistance to ET motivated researchers to try CDK4/6 inhibitors in EBC, both in adjuvant and neoadjuvant settings. While many clinical trials are still ongoing, at least one study and two meta-analyses had shown beneficial results, based on which the US Food and Drug Administration had recently approved the use of one of these agents, abemaciclib, in combination with ET for the adjuvant therapy of patients with high-risk EBC. In this paper, we review the recently published and ongoing landmark clinical trials attempting to expand the use of CDK4/6 inhibitors, in combination with ET, in the adjuvant setting of EBC.

Pharmacoeconomic evaluations of CDK4/6 inhibitors plus endocrine therapy for advanced hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2-) breast cancer: a systematic review

Background

Hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2−) breast cancer is the most common molecular subtype of breast cancer in many countries, and endocrine therapy remains a mainstay in its treatment. Cyclin-dependent kinase (CDK) 4/6 inhibitors are a new class of targeted agents administered orally that are recommended being used in combination with endocrine therapy as first and second line treatments for advanced HR+/HER2− breast cancer. However, their high prices largely hinder using these drugs in real world settings. To offer a new basis for future research, we investigated the cost-effectiveness of combinations of CDK4/6 inhibitors with endocrine therapy in the treatment of advanced HR+/HER2− breast cancer.

Methods

We systematically searched several frequently used databases and identified economic evaluations published from February 2015 to April 2021. The systematic review was performed after retrieving the literatures and extracting data based on inclusion and exclusion criteria. The quality of each selected economic evaluation was assessed by the Consolidated Health Economic Evaluation Reporting Standards (CHEERS).

Results

The literature search yielded 161 articles, among which fourteen studies (15 articles) with CHEER scores ranging from 58.33% to 87.50% entered the final analysis. Markov models were used in most studies. Based on the currently available data, CDK4/6 inhibitors plus endocrine therapy were less cost-effective in first- or second-line treatment of patients with HR+/HER2− advanced breast cancer. However, ribociclib plus letrozole was more cost-effective than palbociclib plus letrozole in the first-line treatment of postmenopausal women. The economic impacts of CDK4/6 inhibitors plus endocrine therapy in non-postmenopausal patients or second-line therapy cannot be fully evaluated due to the limited number of studies. The three most common factors affecting economic outcomes were the prices of CDK4/6 inhibitors, hazard ratios for progression-free survival and overall survival, and health status utility values.

Discussion

CDK4/6 inhibitors plus endocrine therapy have shown significantly improved efficacy outcomes in HR+/HER2− metastatic breast cancer (mBC)/advancer breast cancer (ABC) first-line and second-line treatment for endocrine-sensitive and endocrine-resistant populations, while more potential fields including neoadjuvant and adjuvant settings are being identified to benefit a wider range of breast cancer patients. Meanwhile, risk of severe adverse events that more likely to happen in patients treated with CDK4/6 inhibitors can lead to reduced life quality and higher medical costs patients need to afford. The adverse drug reaction related cost in several economic burden studies were explored to be primarily driven by hospitalizations and outpatient, and assessment of cost associated with CDK4/6 inhibitors adverse events is worth further developing. Drug wastage costs were found higher in palbociclib regimen than ribociclib regimen due to different dosing patterns. Moreover, current economic evaluations showed that ribociclib plus letrozole had better economic benefits than palbociclib plus letrozole for first-line treatment of postmenopausal women with HR+/HER2− ABC.

Vitiligo-Like Lesions in a Patient with Metastatic Breast Cancer Treated with Cyclin-Dependent Kinase (CDK) 4/6 Inhibitor: A Case Report and Literature Review

Background

Cyclin-dependent kinase (CDK) 4/6 inhibitors have revolutionized the treatment landscape of hormone receptor-positive (HR⁺), human epidermal growth factor receptor 2-negative (HER2⁻) metastatic breast cancer, with an impressive efficacy and safety profile. Cytopenia is the main adverse event, which is both predictable and manageable. Here, we report a case of CDK4/6 inhibitor-induced vitiligo-like lesions. Vitiligo or vitiligo-like lesions are a rare adverse event; only a few cases are reported in the literature.

Case Presentation

A 71-year-old female patient was diagnosed initially with early-stage right breast cancer (HR⁺/HER2⁻) and was treated with breast-conserving surgery followed by chemotherapy, radiotherapy, and hormonal therapy. A few years later, she developed metastatic disease to the hilar lymph nodes, and to multiple skeletal sites, including the left scapula, left shoulder, left iliac bone, and dorsal vertebrae, for which she was treated with ribociclib and letrozole. While on treatment, she developed hypopigmented lesions involving both hands, feet, and face, which were described as vitiligo-like lesions.

Conclusion

CDK4/6 inhibitor-induced vitiligo is a rare and unpredictable adverse event. This case report highlights the rarity of this adverse event, the dilemma related to the optimal treatment, and decisions related to continuation, holding, or switching CDK4/6 inhibitors.

Barriers and facilitators to taking CDK4/6 inhibitors among patients with metastatic breast cancer: a qualitative study

PURPOSE

Most studies of adherence to treatment for breast cancer have focused on early-stage patients. Findings from these studies may not generalize to patients with metastatic breast cancer (MBC). The objective of this study was to identify barriers and facilitators of adherence to cyclin-dependent kinase 4/6 (CDK4/6) inhibitors among patients with MBC, guided by the social ecologic model (SEM).

METHODS

Patients with MBC (N = 25), their caregivers (N = 9), and oncology providers (N = 13) completed semi-structured qualitative interviews exploring their experiences with CDK4/6 inhibitors. Interviews were audio-recorded, transcribed verbatim, and analyzed by three raters using a combined deductive and inductive approach.

RESULTS

Qualitative analysis identified barriers and facilitators of adherence at each SEM level. Intrapersonal and interpersonal factors were most frequently discussed. Intrapersonal factors included knowledge/beliefs about CDK4/6 inhibitors, side effects, and establishing a routine. Interpersonal factors included effective communication with/coordination by the care team, support from family and friends, and information from other patients with MBC. Although less frequently discussed, policy factors (i.e., cost of CDK4/6 inhibitors) were of great concern to patients, caregivers, and providers.

CONCLUSION

Barriers to adherence to CDK4/6 inhibitors exist at multiple levels. Our results underscore the potential value of a multilevel intervention (e.g., patient education, evidence-based strategies for symptom management, tips for open and assertive communication with providers, information about financial resources/support available, and so on) to support adherence in this population.

Advances in Analyzing the Breast Cancer Lipidome and Its Relevance to Disease Progression and Treatment

Abnormal lipid metabolism is common in breast cancer with the three main subtypes, hormone receptor (HR) positive, human epidermal growth factor 2 (HER2) positive, and triple negative, showing common and distinct lipid dependencies. A growing body of studies identify altered lipid metabolism as impacting breast cancer cell growth and survival, plasticity, drug resistance, and metastasis. Lipids are a class of nonpolar or polar (amphipathic) biomolecules that can be produced in cells via de novo synthesis or acquired from the microenvironment. The three main functions of cellular lipids are as essential components of membranes, signaling molecules, and nutrient storage. The use of mass spectrometry-based lipidomics to analyze the global cellular lipidome has become more prevalent in breast cancer research. In this review, we discuss current lipidomic methodologies, highlight recent breast cancer lipidomic studies and how these findings connect to disease progression and therapeutic development, and the potential use of lipidomics as a diagnostic tool in breast cancer. A better understanding of the breast cancer lipidome and how it changes during drug resistance and tumor progression will allow informed development of diagnostics and novel targeted therapies.

Predictors for development of palbociclib-induced neutropenia in breast cancer patients as determined by ordered logistic regression analysis

This retrospective study aimed to identify predictors for the development of palbociclib-induced neutropenia. This study retrospectively analysed 78 breast cancer patients who had received palbociclib at our hospital between January 2018 and May 2020. For the regression analysis of factors associated with palbociclib-induced neutropenia, variables were extracted manually from medical charts. The level of palbociclib-induced neutropenia was evaluated using the National Cancer Institute’s Common Terminology Criteria for Adverse Events (version 5). Multivariate ordered logistic regression analysis was performed to identify predictors for the development of neutropenia. Optimal cut-off thresholds were determined using receiver operating characteristic (ROC) analysis. Values of P < 0.05 (2-tailed) were considered significant. Significant factors identified included concomitant use of statin (odds ratio [OR] = 0.104, 95% confidence interval [CI] = 0.018–0.598; P = 0.011) and body mass index (BMI) (OR = 1.118, 95% CI = 1.007–1.241; P = 0.037). ROC analysis revealed that neutropenia (grade 4) was more likely to occur with a BMI ≥ 22.3 kg/m². In conclusion, no concomitant use of statins and high BMI were identified as significant predictors for the development of palbociclib-induced neutropenia.

Endocrine Treatment and Targeted Therapy for Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: ASCO Guideline Update

PURPOSE

To update recommendations of the ASCO systemic therapy for hormone receptor (HR)-positive metastatic breast cancer (MBC) guideline.

METHODS

An Expert Panel conducted a systematic review to identify new, potentially practice-changing data.

RESULTS

Fifty-one articles met eligibility criteria and form the evidentiary basis for the recommendations.

RECOMMENDATIONS

Alpelisib in combination with endocrine therapy (ET) should be offered to postmenopausal patients, and to male patients, with HR-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated, ABC, or MBC following prior endocrine therapy with or without a cyclin-dependent kinase (CDK) 4/6 inhibitor. Clinicians should use next-generation sequencing in tumor tissue or cell-free DNA in plasma to detect PIK3CA mutations. If no mutation is found in cell-free DNA, testing in tumor tissue, if available, should be used as this will detect a small number of additional patients with PIK3CA mutations. There are insufficient data at present to recommend routine testing for ESR1 mutations to guide therapy for HR-positive, HER2-negative MBC. For BRCA1 or BRCA2 mutation carriers with metastatic HER2-negative breast cancer, olaparib or talazoparib should be offered in the 1st-line through 3rd-line setting. A nonsteroidal aromatase inhibitor (AI) and a CDK4/6 inhibitor should be offered to postmenopausal women with treatment-naïve HR-positive MBC. Fulvestrant and a CDK4/6 inhibitor should be offered to patients with progressive disease during treatment with AIs (or who develop a recurrence within 1 year of adjuvant AI therapy) with or without one line of prior chemotherapy for metastatic disease, or as first-line therapy. Treatment should be limited to those without prior exposure to CDK4/6 inhibitors in the metastatic setting.Additional information can be found at www.asco.org/breast-cancer-guidelines.

Efficacy and Safety of CDK4/6 Inhibitors Combined with Endocrine Therapy in HR+/HER-2- ABC Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the efficacy and safety of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors combined with endocrine therapy (ET) for hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER-2-) advanced breast cancer (ABC) patients.

METHODS

We searched clinical trials of CDK4/6 inhibitors combined with ET and calculated the clinical outcomes.

RESULTS

HR+/HER-2- ABC patients treated with CDK4/6 inhibitors combined with ET had significantly prolonged progression-free survival (PFS) and improved objective response rate (ORR) and clinical benefit rate (CBR).

CONCLUSIONS

CDK4/6 inhibitors combined with ET can bring more clinical benefits to ABC patients, and the safety profile is acceptable.

Treatment Experiences with CDK4&6 Inhibitors Among Women with Metastatic Breast Cancer: A Qualitative Study

PURPOSE

To describe patients' perspectives on the use of and potential challenges and barriers with adherence/persistence to cyclin-dependent kinase 4 and 6 inhibitors (CDK4&6i's) to treat metastatic breast cancer (MBC).

METHODS

This qualitative study consisted of 60-minute semi-structured telephone interviews with patients with MBC in the US who were either current or recent CDK4&6i users, identified from administrative claims of survey-eligible commercial and Medicare Advantage patients in the HealthCore Integrated Research Database between November 1, 2018 and November 1, 2019. Patients were recruited by email and/or mailed letter. The 60-minute telephone interviews were conducted by a trained facilitator using a study-developed interview discussion guide that included topics impacting treatment choice and adherence/persistence. Interviews were audio-recorded, transcribed, and thematically analyzed.

RESULTS

All 462 eligible patients were sent a recruitment email and/or letter to which 36 patients responded, consented to participate, and met study inclusion criteria; 25 patients scheduled interviews, and 24 completed them. Study participants were predominately white, non-Hispanic (96%) with a mean age of 59.5 years. Participants reported a largely positive experience and mentioned very few adherence/persistence issues. They further reported appreciating the ease and convenience of oral oncolytics, coped with side effects, had strong medical and social support, and experienced few cost issues.

CONCLUSION

The few adherence/persistence issues reported by participants contrasts with other findings of suboptimal oral oncolytic use. Interview themes indicated several factors that likely contributed to the lack of adherence/persistence issues: trusted relationship with oncologist, belief in importance of medication, positive medication views, strong medical and social support, and minimal personal drug cost. Future research should focus on whether and how much these factors impact adherence/persistence in more diverse populations. If adherence/persistence issues are identified in these populations, then it would be appropriate to study the development of interventions that target factors associated with better adherence/persistence.

A population-based comparison of treatment patterns, resource utilization, and costs by cancer stage for Ontario patients with hormone receptor-positive/HER2-negative breast cancer

PURPOSE

To update and expand on data related to treatment, resource utilization, and costs by cancer stage in Canadian patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer (BC).

METHODS

We analyzed data for adult women diagnosed with invasive HR+/HER2- BC between 2012 and 2016 utilizing the publicly funded health care system in Ontario. Baseline characteristics, treatment received, and health care use were descriptively compared by cancer stage (I-III vs. IV). Resource use was multiplied by unit costs for publicly funded health care services to calculate costs.

RESULTS

Our study included 21,360 patients with stage I-III plus 813 with stage IV HR+/HER2- BC. Surgery was performed on 20,510 patients with stage I-III disease (96.0%), with the majority having a lumpectomy, and radiation was received by 15,934 (74.6%). Few (n = 1601, 7.8%) received neoadjuvant and most (n = 15,655, 76.3%) received adjuvant systemic treatment. Seven hundred and fifty eight patients with metastatic disease (93.2%) received systemic therapy; 542 (66.7%) received endocrine therapy. Annual per patient health care costs were three times higher in the stage IV vs. stage I-III cohort with inpatient hospital services representing nearly 40% of total costs.

CONCLUSION

The costs associated with metastatic HR+/HER2- BC reflect a significant disease burden. Low endocrine treatment rates captured by the publicly funded system suggest guideline non-adherence or that a fair portion of Ontarian patients may be incurring out-of-pocket drug costs.

Comparison of healthcare resource utilization and costs of patients with HR+/HER2- advanced breast cancer treated with ribociclib versus other CDK4/6 inhibitors

AIMS

To assess healthcare resource utilization (HRU) and healthcare costs among women with hormone receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer (HR+/HER2- aBC) treated with cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors.

METHODS

Women with HR+/HER2- aBC, initiating CDK4/6 inhibitor treatment were identified using IBM MarketScan Commercial and Medicare Supplemental databases (Q1/2000-Q3/2018). Based on the first CDK4/6 inhibitor patients received (index therapy), three cohorts were identified: abemaciclib, palbociclib, and ribociclib. The baseline period (six months preceding treatment initiation) was used to describe patient characteristics. All-cause HRU and direct total healthcare costs (medical and pharmacy) from treatment initiation until the earliest of the end of index therapy, continuous health plan enrollment, or data availability, were compared for the ribociclib cohort versus the abemaciclib and palbociclib cohorts, separately, using weighted regression analyses balanced on baseline covariates.

RESULTS

Average age at treatment initiation was ∼60 years and the majority of patients were postmenopausal (abemaciclib: 92%; palbociclib: 92%; ribociclib: 79%). Average follow-up duration was 3.9, 8.8, and 5.9 months for the abemaciclib, palbociclib, and ribociclib cohorts, respectively. After reweighting, HRU was not statistically different between the ribociclib and abemaciclib cohorts, however, the ribociclib cohort incurred significantly lower total healthcare costs (-$5,452; 95% CI: -$8,726; -$1,139, p = .01). Medical costs (driven by outpatient costs) and pharmacy costs (driven by CDK4/6 inhibitor costs) were significantly lower for the ribociclib cohort. Among the reweighted ribociclib and palbociclib cohorts, HRU and total healthcare costs were not statistically different, although the ribociclib cohort had lower outpatient costs per-patient-per-month (-$1,245, 95% CI: -$2,349; -$37, p = .04).

LIMITATIONS

Due to the retrospective, observational design, treatment cohorts were not randomly assigned.

CONCLUSIONS

During CDK4/6 inhibitor therapy, ribociclib patients tended to incur lower medical and pharmacy costs than abemaciclib patients. Among ribociclib and palbociclib patients, HRU and healthcare costs were similar.

CDK4/6 inhibitors in breast cancer: differences in toxicity profiles and impact on agent choice. A systematic review and meta-analysis

Introduction: CDK4/6 inhibitor approval for hormone-responsive breast tumors has significantly changed therapeutic algorithms, with three drugs currently approved.Areas covered: Here, we analyze the toxicity profiles of palbociclib, ribociclib, and abemaciclib through a systematic review and meta-analysis. Palbociclib and ribociclib showed high rates of hematological toxicity, primarily neutropenia, and were associated with a low rate of severe infections. Abemaciclib was associated with a high rate of gastrointestinal toxicities, primarily diarrhea, of grade 1-2 in most cases. Ribociclib was associated with a high rate of hepatic, and respiratory toxicity and with QTc prolongation. The toxicity rate of ribociclib was higher in metastatic patients than non-metastatic patients, with approximately 33% more grade 3-4 toxicities and 21% more grade 3-4 neutropenic events. A 5% higher risk of diarrhea was observed in postmenopausal patients. Pre-treated patients did not show a higher toxicity rate for palbociclib/ribociclib than previously untreated patients, while a 26% higher risk of any grade neutropenia and 6% higher risk of grade 3-4 diarrhea were observed with abemaciclib.Expert opinion: Considering the similar efficacies and indications of palbociclib, ribociclib, and abemaciclib, the evaluation of their toxicity profiles may facilitate treatment choice.

Cancer stem cells: Culprits in endocrine resistance and racial disparities in breast cancer outcomes

Breast cancer stem cells (BCSCs) promote endocrine therapy (ET) resistance, also known as endocrine resistance in hormone receptor (HR) positive breast cancer. Endocrine resistance occurs via mechanisms that are not yet fully understood. In vitro, in vivo and clinical data suggest that signaling cascades such as Notch, hypoxia inducible factor (HIF), and integrin/Akt promote BCSC-mediated endocrine resistance. Once HR positive breast cancer patients relapse on ET, targeted therapy agents such as cyclin dependent kinase inhibitors are frequently implemented, though secondary resistance remains a threat. Here, we discuss Notch, HIF, and integrin/Akt pathway regulation of BCSC activity and potential strategies to target these pathways to counteract endocrine resistance. We also discuss a plausible link between elevated BCSC-regulatory gene levels and reduced survival observed among African American women with basal-like breast cancer which lacks HR expression. Should future studies reveal a similar link for patients with luminal breast cancer, then the use of agents that impede BCSC activity could prove highly effective in improving clinical outcomes among African American breast cancer patients.

Real life efficacy of palbociclib and endocrine therapy in HR positive, HER2 negative advanced breast cancer

BACKGROUND

Palbociclib is indicated for the treatment of hormone receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC), in combination with endocrine therapy. Emerging real-life data suggest that the efficacy of a palbociclib-based therapy is highly conserved. We report the Institut Curie hospital experience.

PATIENTS AND METHODS

We retrospectively reviewed all patients with HR + HER2- ABC treated with a palbociclib-based therapy as first or second line for ABC, with an initial prescription from November 2016 to December 2018. Clinical, laboratory and imaging data were retrieved from electronic records. Data lock was December 31st, 2019. Descriptive analyses, univariate and multivariate Cox regression analyses were performed.

RESULTS

We included 310 consecutive patients. Median age was 61.8 years old. Palbociclib was prescribed in first line in 225 patients (72.6%). Before palbociclib-based therapy initiation, 122 patients (39.3%) were endocrine naive, 96 (31.0%) endocrine sensitive and 92 (29.7%) endocrine resistant. Median follow-up was 20.7 months. Median progression free survival (PFS) was 23.4 months (95%CI: 21.6-NR) in endocrine naive patients, 22.7 months (95%CI: 14.7-NR) in endocrine sensitive, and 13.4 months (95%CI: 10.7-20.8) in endocrine resistant. At 12 months from the initiation of palbociclib, 94.5% of patients were alive. By multivariate analysis, poor prognosis factors for PFS were identified in the endocrine naive/sensitive population: initial ECOG status 2, previous endocrine therapy for ABC, 3 metastatic sites or more. Toxicity profile was similar to previously published data.

CONCLUSION

In a non-selected population of patients with HR + HER2- ABC, the efficacy and safety data are strikingly similar to those previously reported.

Tumor suppression, dose-limiting toxicity and wellbeing with the fetal estrogen estetrol in patients with advanced breast cancer

Purpose

The aim of this study (the ABCE4 study) was to assess dose-limiting toxicity (DLT), safety, tolerability and preliminary efficacy of high doses of the fetal estrogen estetrol (E4) in postmenopausal patients with heavily pretreated, locally advanced and/or metastatic ER+/HER2−breast cancer, resistant to anti-estrogens.

Methods

This was a multicenter, open-label, phase IB/IIA, dose-escalation study with a 3 + 3 cohort design, whereby successive cohorts of three patients received 20 mg, 40 mg or 60 mg E4 per day for 12 weeks by oral administration. DLTs, safety and wellbeing were evaluated after 4, 8 and 12 weeks of treatment. Anti-tumor effects were investigated by computer tomography scanning and evaluated according to RECIST criteria before and after 12 weeks of treatment. Wellbeing was judged weekly by the investigator and by quality-of-life questionnaires by the patients. In view of the small number of patients, no statistical testing was performed.

Results

All 12 patients enrolled had progressive, heavily pre-treated advanced breast cancer. No treatment-related serious adverse events or DLTs occurred during the first 4 weeks of E4 treatment allowing the investigation of all three doses. Five of nine patients completing 12 weeks of E4 treatment showed objective anti-tumor effects and six of nine patients reported improved wellbeing.

Conclusion

High doses of estetrol seem to be safe and are well tolerated during 12 weeks of treatment without dose-limiting toxicity and with anti-tumor effects in five of nine heavily treated patients with progressive, anti-estrogen resistant, advanced breast cancer.

Efficacy and safety of cyclin dependent kinases 4/6 inhibitors in the treatment of metastatic breast cancer: a real-world experience

BACKGROUND

Randomized trials have shown survival gains for patients with metastatic breast cancer (BC) treated with CDK4/6 inhibitors (CDK4/6i) in combination with endocrine agents. It is not unlikely that there may be discrepancies between the generally fit clinical study population and the real-world setting that could affect adherence to treatment guidelines, tolerance to treatment and outcome.

MATERIAL AND METHODS

Consecutive patients with metastatic or locally advanced and unresectable BC that were treated between July 2017 and January 2020 at Karolinska University Hospital, Stockholm, Sweden and that had received at least one dose of CDK4/6i were included in this retrospective study. The primary endpoint was safety, including toxicity according to CTCAE 5 and rates of treatment interruptions, dose reductions and discontinuations. The secondary endpoint was efficacy based on the treating physicians' assessments in terms of progression free (PFS) and overall survival (OS), as well as the factors associated with patient outcome.

RESULTS

Eighty-eight patients were included in the analysis, with a median age of 67.2 years. Grade 4 neutropenia occurred in 9.1% of patients and one episode of neutropenic infection was observed. Dose reductions were made in 38.6% of patients, while 11.4% discontinued treatment due to toxicity, most commonly non-hematologic. After a median follow-up of 18.33 months, median PFS was 13.30 months (95% CI, 11.39-15.21) and median OS could yet not be estimated. In multivariable analysis, number of prior chemotherapy lines was an independent predictor for shorter PFS (HR = 3.28, 95% CI 1.50-7.16, p = .003).

CONCLUSIONS

CDK4/6i administered in a real-world setting exhibits a similar toxicity profile but higher incidence of treatment discontinuation compared to randomized trials. Efficacy of CDK4/6i among patients pretreated with multiple therapy lines is markedly reduced.

Comparative Overall Survival of CDK4/6 Inhibitors Plus Endocrine Therapy vs. Endocrine Therapy Alone for Hormone receptor-positive, HER2-negative metastatic breast cancer

Background: The combination of CDK4/6 inhibitors and endocrine therapy has greatly improved progression-free survival (PFS) in patients with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer in many randomized controlled trials (RCTs). However, the key issue was the extent to which the benefit in PFS could translate into a prolongation of OS.

Methods: We performed a systematical literature search of PubMed, Web of Science, Cochrane Central Register of Clinical Trials and Embase, as well as meeting online archives up to February 2020. The primary outcome was OS, and we performed indirect treatment comparisons depend on a meta-analysis.

Results: Six RCTs were eligible including 3421 breast cancer patients. Compared to the endocrine therapy alone group, adding CDK4/6 inhibitors to endocrine therapy had significantly improved OS (HR=0.76, 95% CI=0.68-0.85, P<0.001). Moreover, the OS advantage was consistent in patients with different combined endocrine therapy, endocrine sensitivity status, sites of distant metastasis, menopausal status and age. Nevertheless, more adverse events were observed in patients treated with CDK4/6 inhibitors. The most common grade 3-4 adverse events were neutropenia (risk ratio [RR]=37.15, 95% CI=15.33-90.04), leucopenia (RR=25.58, 95% CI=13.23-49.46) and anaemia (RR=2.24, 95% CI=1.38-3.85).

Conclusions: Our meta-analysis suggested that compared with endocrine therapy alone, the addition of CDK4/6 inhibitors significantly improved OS in patients with hormone receptor-positive, HER2-negative metastatic breast cancer. However, the addition of CDK4/6 inhibitors also increased the incidences of grade 3-4 adverse events.

Association of Cyclin-Dependent Kinases 4 and 6 Inhibitors With Survival in Patients With Hormone Receptor-Positive Metastatic Breast Cancer: A Systematic Review and Meta-analysis

IMPORTANCE

One of the most recent treatment regimens used for hormone receptor (HR)-positive, ERBB2 (formerly HER2)-negative metastatic breast cancer is treatment with the cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors and endocrine therapy (ET).

OBJECTIVE

To assess overall survival (OS), progression-free survival (PFS), objective response rate, and adverse events, especially grades 3 and 4 adverse events, among patients with HR-positive, ERBB2-negative metastatic breast cancer who were treated with CDK4/6 inhibitors plus ET vs ET alone.

DATA SOURCES

A systematic search of PubMed, Embase, the main oncology conference of the European Society of Medical Oncology, and the American Society of Clinical Oncology and the San Antonio Breast Cancer Symposium databases for randomized clinical trials of CDK4/6 inhibitors plus ET vs ET for HR-positive, ERBB2-negative metastatic breast cancer. Searches were performed up to March 30, 2020.

STUDY SELECTION

A total of 472 records were assessed in PubMed and Embase by 2 authors, including studies, international meeting reports, and reviews. Inclusion criteria were English-language phase 2 or 3 randomized clinical trials of HR-positive, ERBB2-negative metastatic breast cancer, with patients randomly assigned to receive CDK4/6 inhibitors plus ET or ET alone, and having OS or PFS outcomes. The exclusion criteria were phase 1 trials, retrospective studies, or studies without survival outcomes. Excluding the references, 16 articles were relevant. After excluding studies based on exclusion criteria, 9 studies were considered eligible for this meta-analysis.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently extracted data and assessed potential bias. Data assessment followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline. The results were pooled using a fixed-effect model.

MAIN OUTCOMES AND MEASURES

Study heterogeneity was assessed using the I2 statistic. Hazard ratios (HRs) and 95% CIs were used to evaluate PFS, OS, and subgroup analyses. Overall response and 95% CIs were used to evaluate the objective response rate and grade 3 or 4 adverse events. The primary outcome was OS.

RESULTS

In total, 9 studies that included a total of 5043 patients with metastatic breast cancer were assessed in this meta-analysis. Overall, the addition of CDK4/6 inhibitors to ET was associated with a statistically significant benefit to OS (HR, 1.33; 95% CI, 1.19-1.48; P < .001). Compared with ET alone, treatment with CDK4/6 inhibitors plus ET was associated with improved OS for the following subgroups: first-line therapy (HR, 1.35; 95% CI, 1.18-1.54; P < .001), second-line therapy (HR, 1.30; 95% CI, 1.09-1.54; P < .001), premenopausal women (HR, 1.32; 95% CI, 1.04-1.66; P < .001), postmenopausal women (HR, 1.34; 95% CI, 1.18-1.52; P < .001), visceral metastasis (HR, 1.31; 95% CI, 1.12-1.53; P < .001), bone-only metastasis (HR, 1.22; 95% CI, 0.88-1.68; P < .001), age younger than 65 years (HR, 1.25; 95% CI, 1.06-1.49; P < .001), and age 65 years or older (HR, 1.38; 95% CI, 1.11-1.72; P < .001). The addition of CDK4/6 inhibitors to ET was also associated with significant PFS benefit (HR, 1.84; 95% CI, 1.70-1.98; P < .001) and objective response rate benefit (odds ratio, 2.02; 95% CI, 1.61-2.53; P < .001). However, the use of CDK4/6 inhibitors in combination with ET was associated with significantly increased risk of grade 3 or 4 adverse events compared with ET alone, including neutropenia (HR, 57.05; 95% CI, 38.26-85.05; P < .001), leukopenia (HR, 36.36; 95% CI, 19.35-68.34; P < .001), and diarrhea (HR, 4.97; 95% CI, 2.84-8.69; P < .001).

CONCLUSIONS AND RELEVANCE

This meta-analysis indicated that, compared with ET alone, treatment with CDK4/6 inhibitors plus ET was associated with significantly improved OS, PFS, and objective response rate among patients with HR-positive, ERBB2-negative metastatic breast cancer.

Progression-Free Survival and Overall Survival of CDK 4/6 Inhibitors Plus Endocrine Therapy in Metastatic Breast Cancer: A Systematic Review and Meta-Analysis

The introduction of CDK4/6 inhibitors in combination with endocrine therapy (ET) represents the most relevant advance in the management of hormone receptor (HR) positive, HER2-negative metastatic breast cancer over the last few years. This meta-analysis of randomized controlled trials (RCTs) is aimed to better characterize the efficacy of CDK4/6 inhibitors in some relevant subgroups and to test heterogeneity between different compounds with a particular focus on their ability to improve overall survival (OS). Pooled estimates of hazard ratios (HRs) were computed for progression-free survival (PFS), OS, and objective response rate (ORR) analysis in predefined subgroups to better understand treatment effect concerning specific patients’ characteristics. To estimate the absolute benefit in terms of PFS, pooled survival curves were generated by pooling the data of all trials. A total of eight RCTs were included. Adding a CDK4/6 inhibitor to ET is beneficial in terms of PFS, irrespective of the presence or not of visceral metastases, the number of metastatic sites, and the length of the treatment-free interval (TFI). The addition of CDK4/6 inhibitors produces a significant OS improvement, both in aromatase inhibitor (AI)-sensitive (HR 0.75, 95% CI) and AI-resistant patients (HR 0.77, 95% CI [0.67–0.89]). Pooled data from each single drug show that palbociclib remains the only class member not showing a statistically significant HR for OS (HR 0.83, 95% CI [0.68–1.02]).

Efficacy and safety of selective cyclin-dependent kinases 4/6 inhibitors in hormone-receptor-positive, HER2-negative advanced breast cancer - results from a real-world setting

BACKGROUND

Selective cyclin-dependent kinases 4/6 inhibitors (CDKi) have become the standard of care in patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer (ABC). We performed retrospective analysis in patients treated with CDKi in the first year of their routine clinical use in Slovenia.

METHODS

The primary goals were time-to-treatment failure (TTF) and overall survival (OS), analysed via Kaplan-Meier method, the secondary goals were clinical benefit rate (CBR) and safety.

RESULTS

Overall, 218 patients' data were evaluated. The median age was 61.8 years (30.6-84.6). The median number of previous ET lines for ABC was 2 (range 0-5). At the time of inclusion, 128 patients (58.7%) had visceral metastases, 45 patients (20.6%) had bone-only disease. At the median follow-up of 15.2 months, disease progressed in 74 patients and 60 patients died. The median TTF was 8.3 months for the whole group, 19.3, 10.3 and 5.5 months for patients treated in the first-, second- and further lines of systemic therapy, respectively. The median OS from the start of CDKi treatment was not reached in any of the groups. CBR was 59.6% for the whole group, 42.7% for further lines of therapy. The most common grade 3/4 adverse event was neutropaenia in 108 patients (49.5%), followed by an increase of hepatic aminotransferases in 13 patients (6.0%).

CONCLUSIONS

Even in the diverse real-world population treatment with CDKi in combination with ET showed clinical benefit, most prominently in the first- and second lines of systemic therapy.

Phase 1 study of TTC-352 in patients with metastatic breast cancer progressing on endocrine and CDK4/6 inhibitor therapy

PURPOSE

TTC-352 is a selective human estrogen receptor (ER) partial agonist developed for treatment of hormone-refractory ER + breast cancer.

METHODS

This was an accelerated dose escalation study with the primary endpoint of maximum tolerated dose that evaluated five dose levels of TTC-352 in breast cancer progressing after at least two lines of hormonal therapy including one in combination with a CDK4/6 inhibitor. The secondary objectives were to determine treatment tolerability, pharmacokinetics of TTC-352, best response, progression-free survival (PFS), and PKCα expression in tumors.

RESULTS

The study enrolled 15 patients. No dose-limiting toxicity was observed. Patients experienced the following grade 3 toxicities: asymptomatic pulmonary embolism, diarrhea, aspartate transaminase elevation, and myalgia, and one grade 4 toxicity of gamma glutamyltransferase elevation. Pharmacokinetic half-life was 7.6-14.3 h. The intra- and inter-individual variability for AUC₀-∞ hampered assessment of the relationship between dose and AUC₀-∞. Median PFS was 58 days (95% CI = 28,112). Higher PKCα expression in tumor stroma was associated with a trend toward longer PFS.

CONCLUSIONS

TTC-352 demonstrates safety and early clinical evidence of antitumor activity against heavily pretreated hormone-refractory breast cancer. Based upon TTC-352 plasma concentrations and tolerability, the 180 mg twice a day is recommended for further testing. (ClinicalTrials.gov Identifier: NCT03201913).

Metronomic chemotherapy combined with endocrine therapy: are we challenging some dogmas?

INTRODUCTION

Metronomic chemotherapy exerts its effects via inhibition of angiogenesis, immune modulation of the tumoral stroma, induction of senescence and apoptosis of tumor cells. Due to its favorable toxicity profile and its oral administration, metronomic chemotherapy arises as a promising alternative to be combined with endocrine therapy for the treatment of patients with luminal breast cancer.

AREAS COVERED

The present manuscript reviews the rationale supporting the combination of metronomic chemotherapy and endocrine therapy, discussing the studies that evaluated this regimen in the treatment of early-stage and metastatic breast cancer patients. Finally, we conclude by providing an expert opinion on the current role and perspectives for the combination of metronomic chemotherapy and endocrine therapy in the management of patients with luminal breast cancer.

EXPERT OPINION

Retrospective series and early-phase clinical trials have shown promising signs of activity and a favorable toxicity profile with this regimen, which warrants further investigation as a treatment option for luminal breast cancer patients.

Current Therapeutic Progress of CDK4/6 Inhibitors in Breast Cancer

The clinical use of selective cyclin-dependent kinase (CDK) 4/6 inhibitors has significantly improved the prognosis of patients with hormone receptor (HR)-positive human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer (ABC/mBC), which almost achieved the double progression-free survival (PFS) in combination with endocrine therapy (ET) compared with ET alone. To date, there are 3 CDK4/6 inhibitors (palbociclib, ribocilcib and abemaciclib) approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) to treat patients with HR+/HER2-ABC/mBC in the first and later lines. The aim of this review is to summarize the current clinical use and ongoing clinical trials of CDK4/6 inhibitors, the published overall survival data, and the potential biomarkers and resistance to CDK4/6 inhibitors.

Cyclin‑dependent kinase 4/6 inhibitors in combination with fulvestrant for previously treated metastatic hormone receptor‑positive breast cancer patients: A systematic review and meta‑analysis of randomized clinical trials

PURPOSE

To compare the efficacy and safety profile of the combination of cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors and fulvestrant versus fulvestrant alone in previously treated patients with advanced hormone-receptor positive breast cancer.

METHODS

Phase III randomized clinical trials (RCTs) were retrieved from a systematic review of electronic databases. A random-effect model was employed to determine the pooled hazard ratio (HR) for Progression-Free Survival (PFS) and Overall Survival (OS) using the inverse-variance method. The Mantel Haenszel method was used to calculate the pooled odds ratio (OR) for treatment-related side effects. Heterogeneity was measured using the tau-squared and I2 statistics.

RESULTS

Three phase III RCTs (n = 1916) were included in the systematic review. Use of abemaciclib, palbociclib, or ribociclib in combination with fulvestrant was significantly associated with longer PFS compared to use of fulvestrant alone (HR: 0.53; 95%CI: 0.47-0.60; p<0.00001), with no significant heterogeneity found among trials. Similarly, OS was significantly longer for patients who received combination therapy in comparison with those allocated to receive fulvestrant alone (HR: 0.77; 95%CI: 0.67-0.89; p<0.0004). The overall odds ratio of serious adverse events (AE) was not significantly increased with the use of the combination therapy (OR: 1.51; 95%CI: 0.74-3.08), with significant heterogeneity found among trials (tau2=0.34; I2=86%; p = 0.0006).

CONCLUSION

The addition of CDK 4/6 inhibitors (either abemaciclib, palbociclib, or ribociclib) to fulvestrant significantly improved PFS and OS in comparison with fulvestrant alone in patients previously treated with endocrine therapy for advanced breast cancer. No significant heterogeneity was found among CDK 4/6 inhibitors.

Cyclin-dependent kinase 4/6 inhibitors for the management of advanced or metastatic breast cancer in women

PURPOSE

The pharmacology, clinical activity, safety, and place in therapy of the cyclin-dependent kinase (CDK) inhibitors palbociclib, ribociclib, and abemaciclib are reviewed.

SUMMARY

CDK 4 and CDK 6 are downstream agents in the estrogen signaling pathway that control entry into the cell cycle. CDK4/6 inhibition may prevent tumor cell progression in the cell cycle. Three CDK4/6 inhibitors (palbociclib, ribociclib, and abemaciclib) are available for women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. These medications' indications in the treatment of HR+/HER2- advanced breast cancer include use with an aromatase inhibitor (AI) as initial therapy in postmenopausal women and with fulvestrant in women whose disease progressed during endocrine therapy. Ribociclib is also indicated as initial therapy with an AI in premenopausal or perimenopausal women and as initial therapy with fulvestrant in postmenopausal women. Abemaciclib is also indicated as monotherapy in women with disease progression after endocrine therapy and prior chemotherapy. A significant increase in progression-free survival (PFS) was seen with use of all 3 agents as initial therapy with an AI in controlled trials. Each agent also was demonstrated to produce a significant increase in PFS when used with fulvestrant in women whose disease progressed with prior endocrine therapy. Neutropenia is a dose-limiting adverse effect of palbociclib and ribociclib. Fatigue is more common with use of palbociclib and abemaciclib, and gastrointestinal effects are more common with abemaciclib use.

CONCLUSION

CDK4/6 inhibitors have significant demonstrated clinical activity in combination with AIs or fulvestrant in women with HR+/HER2- advanced or metastatic breast cancer and are becoming a standard of care in these patients.

POSEIDON Trial Phase 1b Results: Safety, Efficacy and Circulating Tumor DNA Response of the Beta Isoform-Sparing PI3K Inhibitor Taselisib (GDC-0032) Combined with Tamoxifen in Hormone Receptor Positive Metastatic Breast Cancer Patients

PURPOSE

The strategy of combining endocrine therapy with PI3K-mTOR inhibition has shown promise in estrogen receptor (ER)-positive breast cancer, but new agents and combinations with a better therapeutic index are urgently needed. Taselisib is a potent, selective, beta-isoform-sparing PI3 kinase inhibitor.

PATIENTS AND METHODS

30 patients with ER-positive, metastatic breast cancer who had failed prior endocrine therapy were treated with escalating doses of taselisib (2 or 4 mg in an intermittent or continuous schedule) combined with tamoxifen 20 mg once daily in this phase 1b study using a "rolling six" design.

RESULTS

Taselisib combined with tamoxifen was generally well tolerated, with treatment-emergent adverse events as expected for this class of drugs, including diarrhea (13 patients, 43%), mucositis (10 patients, 33%), and hyperglycemia (8 patients, 27%). No dose-limiting toxicities were observed. Objective responses were seen in 6 of 25 patients with RECIST-measurable disease (ORR 24%). Median time to disease progression was 3.7 months. Twelve of 30 patients (40%) had disease control for 6 months or more. Circulating tumor (ct)DNA studies using next-generation tagged amplicon sequencing identified early indications of treatment response and mechanistically relevant correlates of clinical drug resistance (e.g., mutations in KRAS, ERBB2) in some patients.

CONCLUSIONS

Taselisib can be safely combined with tamoxifen at the recommended phase 2 dose of 4 mg given once daily on a continuous schedule. Preliminary evidence of antitumor activity was seen in both PIK3CA mutant and wild-type cancers. The randomized phase 2 part of POSEIDON (testing tamoxifen plus taselisib or placebo) is currently recruiting.

Cyclin-Dependent Kinases 4/6 Inhibitors in Breast Cancer: Current Status, Resistance, and Combination Strategies

Dysregulated activation of the cyclin-dependent kinases (CDKs) 4/6, leading to uncontrolled cell division, is hallmark of cancers. Further study of the cell cycle will advance the cancer treatment. As powerful and effective drugs, inhibitors of CDK 4/6 have been widely used in clinical practice for several malignancies, particularly against breast cancers driven by the estrogen receptor (ER). Three CDK4/6 inhibitors, including palbociclib (PD0332991), ribociclib (LEE011) and abemaciclib (LY2835219), have been approved by the US Food and Drug Administration (FDA) for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced or metastatic breast cancer. However, CDK4/6 inhibitors act downstream of many mitogenic signaling pathways, and this has implications for resistance. It is worth to note that the mechanisms of resistance are not very clear. Up to now, a small number of preclinical and clinical studies have explored potential mechanisms of CDK4/6 inhibitors resistance in breast cancer. On this basis, rational and effective combination therapy is under development. Here we review the current knowledge about the mechanisms and efficacy of CDK4/6 inhibitors, and summarize data on resistance mechanisms to make future combination therapies more accurate and reasonable.

Hydrogen Bonds in Protein-Ligand Complexes

Fast and reliable evaluation of the hydrogen bond potential energy has a significant impact in the drug design and development since it allows the assessment of large databases of organic molecules in virtual screening projects focused on a protein of interest. Semi-empirical force fields implemented in molecular docking programs make it possible the evaluation of protein-ligand binding affinity where the hydrogen bond potential is a common term used in the calculation. In this chapter, we describe the concepts behind the programs used to predict hydrogen bond potential energy employing semi-empirical force fields as the ones available in the programs AMBER, AutoDock4, TreeDock, and ReplicOpter. We described here the 12-10 potential and applied it to evaluate the binding affinity for an ensemble of crystallographic structures for which experimental data about binding affinity are available.

Hepatic arterial therapy with oxaliplatin and systemic capecitabine for patients with liver metastases from breast cancer

OBJECTIVES

Hepatic arterial treatment (HAT) for liver metastases in patients with metastatic breast cancer (MBC) has only been investigated in few studies.

MATERIALS AND METHODS

Two phase II trials were initiated simultaneously to evaluate capecitabine in combination with oxaliplatin in patients with MBC and liver metastases. These two trials are reported together. Continuous capecitabine (1300 mg/m2) was combined with oxaliplatin (85 mg/m2) alternating between systemic treatment and HAT followed by degradable starch microspheres with EmboCept^® S every second week. Four patients participated in a pharmacokinetic analysis of oxaliplatin. Each patient had samples taken when receiving oxaliplatin systemically and as HAT with and without EmboCept^® S.

RESULTS

Totally, 52 patients received HAT: 14 with liver metastases only and 38 patients with additional limited metastatic disease. The patients had previously received a median of 2 (range 0-6) chemotherapeutic regimens for MBC. The response rate was 42.3% (95% confidence interval (CI) 28.7-56.8%) with 7.7% complete and 34.6% partial responses. Median progression free survival was 10.8 months (95% CI 6.9-14.7 months) and median overall survival 27.6 months (95% CI 20.4-34.8 months). The toxicity was moderate with hand-foot syndrome (15.4%), neuropathy (9.6%), fatigue (9.6%), and abdominal pain (9.6%) being the most common grade 3 adverse events. There was no clear difference between systemic blood concentrations of oxaliplatin when given systemic or as HAT.

CONCLUSION

HAT oxaliplatin in combination with capecitabine is safe and efficient in patients with MBC. The results are promising with high response rates and a long median progression free and overall survival.