Hormone Receptor-positive Advanced Breast Research Articles

Abstract OT2-02-07: Fulvestrant with additional palbociclib in advanced or metastatic hormone receptor-positive HER2-negative breast cancer after progression to fulvestrant monotherapy: JBCRG- M07 (FUTURE trial)

Abstract Background: Fulvestrant is one of the standard treatments for first- and second-line endocrine therapy for hormone receptor (HR)-positive metastatic breast cancer (MBC). Palbociclib inhibits cyclin dependent kinase (CDK) 4 and CDK6 in vitro, resulting in loss of RB1 phosphorylation. Palbociclib has high activity in HR-positive breast cancer cell lines and is synergistic in combination with endocrine therapies. The PALOMA-3 trial enrolled patients with metastatic estrogen receptor (ER)-positive breast cancer with resistance to aromatase inhibitor. The results demonstrated that palbociclib combined with fulvestrant was associated with significantly longer progression-free survival (PFS) than fulvestrant alone. However, patients in the trial reported higher rates of adverse events, such as neutropenia and alopecia, compared with fulvestrant monotherapy. We investigate in this prospective cohort study that the addition of palbociclib to fulvestrant is effective and safe in HR-positive and HER2-negative advanced breast cancers that progressed during fulvestrant monotherapy. Specific Aims: Primary objective: To observe the PFS in patients with resistance to fulvestrant monotherapy who were treated with fulvestrant plus palbociclib. Secondary Objective: To observe the PFS in patients treated with fulvestrant as the first and second line therapy. We also aim to observe overall survival and safety. A prospective translational research is also planned to assess the correlations between biomarkers and response. Trial Design: Single arm exploratory trial Eligibility Criteria: Eligible patients must have historically confirmed ER-positive and HER2-negative MBC who received fulvestrant as first or second line therapy. Prior chemotherapy in the neoadjuvant and adjuvant settings and up to one line of chemotherapy in MBC is permissible. Patients who received CDK4/6 inhibitor as metastatic therapy are excluded. Statistical Design: We aim to set the lowest limit of the therapeutic effect at a median PFS of 5 months, which is the value reported in the PALOMA-3 study. If we assume that the expected median PFS is 8 months, at least 63 patients are required to reject the null hypothesis (5 months) with a power of 80% under a one-sided alpha at 0.05. The length of the accrual period and follow-up period are set at 12 and 18 months, respectively. Target Accrual: First registration: 200 patients with fulvestrant monotherapy as the first and second line setting. Second registration: 70 patients with combined palbociclib and fulvestrant. (UMIN 000029294) Citation Format: Kokoro Kobayashi, Naoki Niikura, Shigehira Saji, Takayuki Iwamoto, Nobutaka Iwakuma, Yuichiro Kikawa, Norikazu Masuda, Kenichi Watanabe, Takashi Takeshita, Mari Oba, Shinji Ohno. Fulvestrant with additional palbociclib in advanced or metastatic hormone receptor-positive HER2-negative breast cancer after progression to fulvestrant monotherapy: JBCRG- M07 (FUTURE trial) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT2-02-07.

First-line endocrine therapy for postmenopausal patients with hormone receptor-positive, HER2-negative metastatic breast cancer: a systematic review and meta-analysis

BackgroundIn establishing the 2018 Breast Cancer Practice Guidelines of the Japan Breast Cancer Society, we explored the optimal first-line endocrine therapy for advanced postmenopausal hormone receptor-positive breast cancer.MethodsWe performed a systematic review of relevant reports from randomized-controlled studies published prior to November 2016 found using medical journal search engines. The main outcomes which we evaluated were progression-free survival (PFS), objective response rate (ORR), disease control rate (CBR), and toxicity.ResultsFour controlled trials comparing aromatase inhibitors (AI) and cyclin-dependent kinase (CDK)4/6 inhibitor combination therapy to AI monotherapy, and two controlled trials comparing anastrozole to fulvestrant 500 mg were analyzed. AI/CDK4/6 inhibitor combination therapy significantly improved PFS (Risk Ratio: 0.67, 95%CI 0.60–0.73), increased ORR (Risk Difference: 0.11, 95% CI 0.07–0.16), and increased CBR (Risk Difference: 0.11, 95% CI 0.07–0.15), compared with AI monotherapy. Patients who received this combination therapy had a higher grade ≥ 3 adverse event rate more than those who received AI monotherapy (Risk Difference: 43%, 95%CI: 0.39–0.47). Fulvestrant 500 mg alone significantly improved PFS (risk ratio: 0.85, 95%CI 0.72–0.98), but ORR and CBR were similar to those of anastrozole alone.ConclusionIn the first-line treatment for advanced postmenopausal hormone receptor-positive breast cancer, a combination therapy of CDK4/6 inhibitors and AI showed significant improvement of PFS, ORR, and CBR but with significant increased toxicities compared with AI alone. Fulvestrant 500 mg monotherapy significantly prolonged PFS compared with AI monotherapy. We must wait for the results of the studies with longer follow-up period.

Efficacy of Palbociclib and Endocrine Treatment in Heavily Pretreated Hormone Receptor-positive Her2-negative Advanced Breast Cancer: Retrospective Multicenter Trial

Efficacy of Palbociclib and Endocrine Treatment in Heavily Pretreated Hormone Receptor-positive Her2-negative Advanced Breast Cancer: Retrospective Multicenter Trial

Torin2 Exploits Replication and Checkpoint Vulnerabilities to Cause Death of PI3K-Activated Triple-Negative Breast Cancer Cells.

Frequent mutation of PI3K/AKT/mTOR signaling pathway genes in human cancers has stimulated large investments in targeted drugs but clinical successes are rare. As a result, many cancers with high PI3K pathway activity, such as triple-negative breast cancer (TNBC), are treated primarily with chemotherapy. By systematically analyzing responses of TNBC cells to a diverse collection of PI3K pathway inhibitors, we find that one drug, Torin2, is unusually effective because it inhibits both mTOR and other PI3K-like kinases (PIKKs). In contrast to mTOR-selective inhibitors, Torin2 exploits dependencies on several kinases for S-phase progression and cell-cycle checkpoints, thereby causing accumulation of single-stranded DNA and death by replication catastrophe or mitotic failure. Thus, Torin2 and its chemical analogs represent a mechanistically distinct class of PI3K pathway inhibitors that are uniquely cytotoxic to TNBC cells. This insight could be translated therapeutically by further developing Torin2 analogs or combinations of existing mTOR and PIKK inhibitors.

Alpelisib for PIK3CA-Mutated, Hormone Receptor–Positive Advanced Breast Cancer

BackgroundPIK3CA mutations occur in approximately 40% of patients with hormone receptor (HR)–positive, human epidermal growth factor receptor 2 (HER2)–negative breast cancer. The PI3Kα-specific inhibitor alpelisib has shown antitumor activity in early studies.MethodsIn a randomized, phase 3 trial, we compared alpelisib (at a dose of 300 mg per day) plus fulvestrant (at a dose of 500 mg every 28 days and once on day 15) with placebo plus fulvestrant in patients with HR-positive, HER2-negative advanced breast cancer who had received endocrine therapy previously. Patients were enrolled into two cohorts on the basis of tumor-tissue PIK3CA mutation status. The primary end point was progression-free survival, as assessed by the investigator, in the cohort with PIK3CA-mutated cancer; progression-free survival was also analyzed in the cohort without PIK3CA-mutated cancer. Secondary end points included overall response and safety.ResultsA total of 572 patients underwent randomization, including 341 patients with confirmed tumor-tissue PIK3CA mutations. In the cohort of patients with PIK3CA-mutated cancer, progression-free survival at a median follow-up of 20 months was 11.0 months (95% confidence interval [CI], 7.5 to 14.5) in the alpelisib–fulvestrant group, as compared with 5.7 months (95% CI, 3.7 to 7.4) in the placebo–fulvestrant group (hazard ratio for progression or death, 0.65; 95% CI, 0.50 to 0.85; P<0.001); in the cohort without PIK3CA-mutated cancer, the hazard ratio was 0.85 (95% CI, 0.58 to 1.25; posterior probability of hazard ratio <1.00, 79.4%). Overall response among all the patients in the cohort with PIK3CA-mutated cancer was greater with alpelisib–fulvestrant than with placebo–fulvestrant (26.6% vs. 12.8%); among patients with measurable disease in this cohort, the percentages were 35.7% and 16.2%, respectively. In the overall population, the most frequent adverse events of grade 3 or 4 were hyperglycemia (36.6% in the alpelisib–fulvestrant group vs. 0.7% in the placebo–fulvestrant group) and rash (9.9% vs. 0.3%). Diarrhea of grade 3 occurred in 6.7% of patients in the alpelisib–fulvestrant group, as compared with 0.3% of those in the placebo–fulvestrant group; no diarrhea of grade 4 was reported. The percentages of patients who discontinued alpelisib and placebo owing to adverse events were 25.0% and 4.2%, respectively.ConclusionsTreatment with alpelisib–fulvestrant prolonged progression-free survival among patients with PIK3CA-mutated, HR-positive, HER2-negative advanced breast cancer who had received endocrine therapy previously. (Funded by Novartis Pharmaceuticals; SOLAR-1 ClinicalTrials.gov number, NCT02437318.)

Abstract PD2-04: Baseline circulating ESR1 mutation analysis in the randomised phase III EFECT study of fulvestrant versus exemestane in advanced hormone receptor positive breast cancer

Abstract Background. ESR1 mutations are acquired frequently in hormone receptor positive breast cancer after treatment with aromatase inhibitors (AI) in the metastatic setting. In prior analysis of the SoFEA phase III randomised trial, we demonstrated the detection of ESR1 mutations in circulating tumor DNA (ctDNA) predicted for greater benefit of fulvestrant compared to exemestane (Fribbens et al JCO 2016). Methods. The phase III EFECT study randomised 693 patients with ER+ metastatic breast cancer who had progressed on a prior non-steroidal AI, between fulvestrant loading dose and then 250mg q28 days and exemestane (Chia S, et al. J Clin Oncol 2008). Baseline serum samples were available from 227 patients in EFECT, and were analysed for the 8 most common ESR1 mutations by multiplex digital PCR. The association between baseline ESR1 status and time to progression (TTP) was analysed using Kaplan-Meier methods. Results. ESR1 mutations were successfully analysed in 98% (222/227) of patients with baseline serum samples, with ESR1 mutations detected in 23.4% (52/222) samples. Overall, detection of ESR1 mutations at baseline was associated with shorter TTP (hazard ratio [HR] 2.03, 95% CI 1.26-3.29, p=0.004). In patients with ESR1 mutation detected, TTP was 2.0 months (95%CI, 1.7-2.4) on exemestane and 3.5 months (95%CI, 1.9-5.0) on fulvestrant (HR 0.67, 95%CI 0.37-1.19, p=0.17). In patients without ESR1 mutations detected, TTP was 4.5 months (95%CI, 3.7-5.6) on exemestane and 3.7 months (95%CI, 3.3-5.2) on fulvestrant (HR 1.05, 95%CI 0.75-1.45, p=0.78). A meta-analysis of SoFEA and EFECT will be presented at the conference. Conclusions. Historical serum samples may be used for ctDNA analysis, illustrating the potential for future research of sample archives. Patients with ESR1 mutation detected in ctDNA have poor outcome when treated with exemestane, replicating prior results from SoFEA and demonstrating clinical utility for ESR1 mutation ctDNA analysis. Citation Format: Turner N, Swift C, Kilburn L, Garcia-Murillas I, Johnston S, Budzar A, Robertson J, Gradishar W, Piccart M, Schiavon G, Chia S. Baseline circulating ESR1 mutation analysis in the randomised phase III EFECT study of fulvestrant versus exemestane in advanced hormone receptor positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD2-04.

Abstract P2-07-05: A clinical calculator to predict disease outcomes in women with hormone receptor-positive advanced stage breast cancer treated with first-line endocrine therapy

Abstract Purpose: Endocrine based therapy is an effective strategy to manage hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC). However, nearly all patients exhibit/develop either de novo or acquired resistance. While prognostic biomarkers of endocrine responsiveness are well established for the adjuvant treatment in ER+ breast cancer, less is known regarding prognostic and predictive biomarkers of response in the first line ABC setting. We sought to develop a clinical calculator based on clinical criteria for predicting progression-free survival (PFS) and overall survival (OS) of women with HR+/HER2- ABC who will be receiving endocrine monotherapy as first-line treatment for ABC. Methods: The development of the clinical calculator will be based on data from modern clinical trials in women with HR+/HER2- ABC. The studies to be included in the final analyses are given in Table 1. The control arm data from trials1-6 will form the training dataset (N = 1,223) and be used to construct the clinical prediction models. Variables considered include age, race, ECOG status, disease measurability, body mass index, disease-free interval, number of metastatic sites, locations of metastatic sites, prior endocrine therapy, and prior chemotherapy. Missing values will be imputed using single imputation with all variables included in the imputation model. For continuous variables, restricted cubic splines will be used to determine if non-linear effects may be more appropriate. The Lasso regression will be used as a variable selection technique to reduce the dimensionality of covariates; initially all pairwise interactions will be included in the model. Following Lasso regression, the multivariable Cox proportional hazards models will be constructed for PFS and OS including only variables retained in Lasso. The final model will be internally validated for discrimination and calibration using 10-fold cross-validation. External validation will be performed using control arm data from EGF 30008 (N = 536). Results: To date, control arm data from four trials (trials 1-4) have been received. The preliminary results presented here are based on pooled data from C40503 and LEA, for which data elements have been harmonized. Models for predicting PFS and OS have good calibration and are associated with bias-corrected C-indices of 0.61 and 0.65, respectively. These models will be updated using pooled data from trials 1-6. Conclusions: Our preliminary data demonstrate that clinical calculators based on baseline clinical factors can provide accurate prediction of PFS and OS in patients with HR+/HER2- ABC treated with first-line ET. If validated, these tools may be used for risk stratification in future clinical trials and to identify patients who may require more or less aggressive therapy. Table 1:Studies to be includedTrial NumberTrial NameTrial PISample Size in Control Arm1C40503Maura Dickler152 (letrozole)2LEAMiguel Martin179 (letrozole)3FACTJonas Bergh188 (anastrozole)4FALCONJohn Robertson194 (anastrozole)5S0226Rita Mehta345 (anastrozole)6MONARCH 3Matthew Goetz165 (nonsteroidal AI)7EGF 30008Stephen Johnston536 (letrozole) Citation Format: Polley M-YC, Dickler MN, Johnston S, Goetz MP, de la Haba J, Loibl S, Mehta RS, Bergh J, Roberston J, Barlow W, Liu H, Tenner K, Martin M. A clinical calculator to predict disease outcomes in women with hormone receptor-positive advanced stage breast cancer treated with first-line endocrine therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-07-05.

Abstract P6-18-23: Palbociclib and endocrine therapy in fourth line and beyond for hormone receptor-positive HER2-negative advanced breast cancer: The UK compassionate access program experience

Abstract Background Palbociclib is approved in 1st line for hormone receptor (HR)-positive HER2-negative advanced breast cancer (ABC). A Compassionate Access Program (CAP) previously allowed patients to receive it in 4th line. However, Palbociclib has not been specifically tested in this population. We aimed to determine the safety and efficacy profile of Palbociclib within the CAP across ten institutions in the United Kingdom. Methods We retrospectively identified HR-positive HER2-negative ABC patients on the Palbociclib CAP between December 2015 and September 2017. Demographics, disease characteristics, prior treatments, blood tests, toxicities, treatment delays and responses were recorded. Simple statistics, Fisher's exact test, chi-squared method and Cox regression were used as appropriate. Results 118 patients identified had median age of 59 (32-82). 97 (82.20%) were postmenopausal and 109 (92.37%) had ECOG Performance Status 0-1. 96 (81.36%) had visceral involvement, 19 (16.10%) bony only and 15 (12.71%) visceral only disease. Patients received a median 5 (range 3-11) prior lines of treatment and 3 (range 0-8) prior chemotherapy lines. 105 patients (89.74%) developed neutropenia (grade ≥3 in 59 [56.19%]). 6 experienced febrile neutropenia (5.13%). 57 (48.72%) had a dose reduction, down to 100mg in 48 (41.03%) and 75mg in 9 (7.69%) due to hematologic toxicity in 46 (80.70%). Dose delays were in median 7 days long (range: 0-56). Palbociclib was discontinued due to disease progression in 97 (82.91%) and to toxicity in 5 (4.27%). Grade 3 neutropenia occurred in 45 patients (67.16%) who received ≥3 and in 22 (32.84%) who received &amp;lt;3 prior chemotherapies (p 0.351). Palbociclib produced clinical benefit rate (CBR) of 47.52% and overall response rate of 15.84% in 101 patients assessed. CBR was 45.45% with previous endocrine treatment (ET) progression-free survival (PFS) &amp;lt;6 months versus 49.12% if PFS ≥6 months (p 0.714). Overall, median PFS was 4.5 months (95% CI 3.7-5.9). The PFS seen in different subgroups showed no impact in relation to the number of lines of prior chemotherapy (&amp;lt;3 lines: 5.9 months [95% CI 3.7-11.0]; ≥3 lines: 4.3 months [95% CI 3.3-5.5], p 0.159), but was numerically greater in those who had previous benefit from ET (PFS ≥6 months: 5.9 months [95% CI 4.4-8.0]; &amp;lt;6 months: 3.7 months [95% CI 2.8-4.5], p. 0.055) or in those with bone only disease (bone only: 11.0 months [95% CI 2.3-not reached]; other sites involved: 4.4 months [95% CI 3.6-5.5], p 0.024). Median OS was 15.8 months (95% CI 13.3-18.7) for the whole cohort and it was greater in patients who derived longer PFS from prior ET (≥6 months: 18.1 months [95% CI 13.0-NR]; &amp;lt;6 months: 14.4 months [95% CI 7.7-18.3], p. 0.052). Conclusions To date, this is the most extensive analysis of Palbociclib outcomes in ≥4th-line setting. In this heavily pretreated population clinical benefit was confirmed particularly for endocrine-sensitive disease and predominantly involving the bones and in earlier lines of treatment. Grade ≥3 neutropenia rates were similar to PALOMA trials, but the higher incidence of febrile neutropenia need to be carefully considered. Citation Format: Battisti NML, Kingston B, King J, Denton A, Waters S, Sita-Lumsden A, Rehman F, Stavraka C, Kristeleit H, Sawyer E, Houghton D, Davidson N, Howell S, Choy J, Harper P, Roylance R, Fharat R, Mohammed K, Ring A, Johnston S. Palbociclib and endocrine therapy in fourth line and beyond for hormone receptor-positive HER2-negative advanced breast cancer: The UK compassionate access program experience [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-23.

Abstract OT1-12-04: A phase IIIb, open-label, local, multicenter study of the molecular features of postmenopausal women with hormone receptor-positive (HR+) HER2-negative advanced breast cancer on first-line treatment with ribociclib and letrozole (BioItaLEE)

Abstract Background: characterizing the molecular features associated with prolonged benefit from CDK 4/6 inhibitors in HR+ HER2- BC and the acquired genomic alterations following treatment progression remains an unmet need and is crucial for leveraging the efficacy of CDK4/6 inhibitors and for elucidating resistance mechanisms. Identifying pre-treatment or pharmacodynamic predictive markers of treatment benefit, as well as predictive markers of toxicity by correlating pharmacogenomics with adverse events, could help physicians to select patients who may benefit the most from these therapies and improve the clinical management. Trial design: this is an Italian, multicenter, open-label, single-arm trial (NCT03439046) enrolling approximately 350 HR+ HER2- aBC first line patients in 48 sites. Patients are treated with ribociclib and letrozole and eligibility criteria are similar to the MONALEESA-2 trial. Patients will be followed for safety and efficacy outcomes. An extensive prospective collection of biological samples at different time points will be performed as follow: whole blood and plasma at baseline, cycle 1-D15, cycle 2-D1, at first imaging evaluation, at cycle 24-D1, as well as upon progression of disease; newly obtained tissue biopsies at baseline and at progression; a buccal swab for pharmacogenetics at baseline. Efficacy and safety data will be collected for all patients. Aims: the primary objective of this study is to identify circulating tumor DNA (ctDNA) alterations at baseline, to describe their evolution during treatment and to evaluate the association with clinical outcome. An optimized Next Generation Sequencing approach for the detection of low abundance events in ctDNA will be adopted. Single nucleotide variants and copy number alterations in a customized panel of genes relevant for BC will be analyzed. Secondary objectives include the evaluation of: serum thymidine kinase 1 activity over time as blood marker of early response; ctDNA alterations across different patient profiles and clonal evolution of ctDNA alterations under treatment; ctDNA alterations at time of tumor progression; correlation between mutational status detected in ctDNA and matched tissue samples; features of tumor microenvironment before and after treatment; association of pharmacogenomics patterns with adverse events and clinical outcomes. Clinical efficacy and safety of ribociclib + letrozole will be correlated with all biological endpoints. Statistical methods: the study is descriptive in nature and no formal statistical testing is necessary or applicable. Sample size is aligned with other biomarker studies and is based on a feasibility analysis of the trial and relative timelines. Present accrual: The first study patient was screened in Feb 2018, as in June 2018, 126 patients have been screened and 78 patients have been enrolled. Citation Format: De Laurentiis M, Arpino G, Bianchini G, Malorni L, Castelletti D, De Vecchi R, Grasso D. A phase IIIb, open-label, local, multicenter study of the molecular features of postmenopausal women with hormone receptor-positive (HR+) HER2-negative advanced breast cancer on first-line treatment with ribociclib and letrozole (BioItaLEE) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-12-04.

Exploring Biomarkers of Phosphoinositide 3-Kinase Pathway Activation in the Treatment of Hormone Receptor Positive, Human Epidermal Growth Receptor 2 Negative Advanced Breast Cancer.

Resistance to endocrine therapy (ET) is common in patients with hormone receptor positive (HR+) advanced breast cancer (ABC). Consequently, new targeted treatment options are needed in the post-ET setting, with validated biomarkers to inform treatment decisions. Hyperactivation of the phosphoinositide 3-kinase (PI3K) signaling pathway is common in ABC and is implicated in resistance to ET. The most frequent mechanism of PI3K pathway activation is activating mutations or amplification of PIK3CA, which encodes the α-isoform of the catalytic subunit of PI3K. Combining buparlisib, a pan-PI3K-targeted agent, with ET demonstrated modest clinical benefits in patients with aromatase inhibitor-resistant, HR+, human epidermal growth receptor 2 negative (HER2-) ABC in two phase III trials. Importantly, greater efficacy gains were observed in individuals with PIK3CA-mutated disease versus PIK3CA-wild-type tumors. Although the challenging safety profile did not support widespread use of this treatment combination, isoform-selective PI3K inhibitors may improve tolerability. In early clinical trials, promising disease control benefits were demonstrated with the PI3K isoform-selective inhibitors alpelisib and taselisib in patients with PIK3CA-mutated HR+, HER2- ABC. Ongoing biomarker-guided phase II/III studies may provide further opportunities to identify patients most likely to benefit from treatment with PI3K inhibitors and provide insight into optimizing the therapeutic index of PI3K inhibitors. Challenges facing the implementation of routine PIK3CA mutation testing must be addressed promptly so robust and reproducible genotyping can be obtained with liquid and tumor biopsies in a timely and cost-effective manner. IMPLICATIONS FOR PRACTICE: The development of phosphoinositide 3-kinase (PI3K) inhibitors, especially those that selectively target isoforms, may be an effective strategy for overcoming endocrine therapy resistance in hormone receptor positive, human epidermal growth receptor 2 negative advanced breast cancer. Early-phase studies have confirmed that patients with PIK3CA mutations respond best to PI3Kα-isoform inhibition. Ongoing phase III trials will provide further data regarding the efficacy and safety of PI3K inhibitors in patients with different biomarker profiles.

Why upfront use of CDK inhibitors for the treatment of advanced breast cancer may be wasteful, and how we can increase their value

Three Cyclin Dependent Kinase 4/6 (CDK) inhibitors have been approved by the United Stated Food and Drug Administration for front line treatment of advanced hormone receptor positive breast cancer based on improvements in progression free survival against endocrine monotherapy. Two clinical trials have so far reported results on overall survival but both are negative. CDK inhibitors are usually tolerated well but they do add to inconvenience and cost - for example, grade III-IV neutropenia occur at a frequency of over 60% requiring frequent blood work at least during the initial months of treatment. These drugs cost over $ 13,500 for a 4-week cycle in the United States, and are responsible for billions of dollars annually in drug cost alone. Importantly, many women with metastatic breast cancer do well for a long time with endocrine therapy alone and CDK inhibitors do not have a predictive marker. Selective use of these agents in later lines may improve substantially the convenience and cost without compromise in overall outcome. However, with results demonstrating impressive improvements in PFS published in major medical journals coupled with patients' natural desire for “best available” options, the trend among oncologists is to prescribe these drugs as the default front-line treatment. In this commentary I caution readers against over interpretation of results from the CDK inhibitor trials, describe adverse consequences of routine front-line use, and explain why selective use in later line may yield a higher value.

The efficacy and safety of targeted therapy plus fulvestrant in postmenopausal women with hormone-receptor positive advanced breast cancer: A meta-analysis of randomized-control trials.

ObjectiveTo evaluate the efficacy and safety of targeted therapy plus fulvestrant for postmenopausal patients with hormone receptor-positive advanced breast cancer.MethodsPubmed, Embase and Web of Science databases were systematically searched on February 26, 2018. Eligible studies were screened according to selection criteria, and two reviewers independently extracted outcome data which included progression-free survival, overall survival, objective response rate, clinical benefit rate and toxicities. RevMan 5.3 and STATA 11.0 software were used to conduct meta-analysis.ResultsThirteen articles including twelve randomized-control trials fulfilled selection criteria. There was no evidence regarding the existence of publication bias and high-risk bias of quality in the selected studies. In previously endocrine therapy-treated postmenopausal patients with hormone-receptor positive advanced breast cancer, the PFS (HR = 0.77, 95%CI: 0.66–0.91) and ORR (RR = 1.78, 95%CI: 1.35–2.34) of combination therapy group were significantly higher than that from fulvestrant monotherapy group. Besides, a statistically significant difference in PFS was found across the two arms in postmenopausal women with PIK3CA-mutant ctDNA tumor (HR = 0.52, 95% CI: 0.39–0.69). Moreover, the risk of adverse events (RR = 1.09, 95%CI: 1.05–1.13), CTCAE≥3 (RR = 1.97, 95%CI: 1.49–2.60) and discontinuation due to adverse events (RR = 4.91, 95%CI: 3.37–7.15) were also significantly different between two treatment groups. Sensitivity analysis showed PLOMA-3 trial was an important factor of heterogeneity.DiscussionEven though the combination of targeted therapy plus fulvestrant improved PFS and increased ORR in advanced breast cancer patients, the toxicities of combination therapy were also higher than fulvestrant monotherapy. Further studies related to inhibitors targeting the specific signaling pathway or receptors are urgently needed, and more efforts concerning precision medicine of targeted therapy plus endocrine therapy should be taken to improve the clinical benefits.

Clinical benefit of fulvestrant monotherapy in the multimodal treatment of hormone receptor and HER2 positive advanced breast cancer: a case series.

Fulvestrant is a pure estrogen receptor (ER) antagonist approved for the treatment of metastatic ER positive breast cancer in postmenopausal women with disease progression following antiestrogen therapy. The clinical results of fulvestrant demonstrated encouraging activity in tumors in spite of HER2 positivity, but data about its use after progression on anti-HER2 agents are limited. Partial responses and durations of response of 12, 25, and 38 months in three cases with multiple metastases of ER positive and HER2 positive breast cancer were observed; all patients had been treated with 1–4 regimens of an anti-HER2 agent in combination with chemotherapy or an aromatase inhibitor before the initiation of fulvestrant. Fulvestrant is a valuable option with limited toxicity and durable response in metastatic HER2 and ER positive breast cancer after progression on anti-HER2 agents as well. Therapeutic benefit even in extensive skin metastases and (irradiated) brain metastases may be expected. Further investigations are warranted to establish where it fits into the multimodal management of ER and HER positive breast cancer.

Mutational Profile of Metastatic Breast Cancer Tissue in Patients Treated with Exemestane Plus Everolimus.

Background Everolimus has been shown to overcome endocrine resistance in hormone receptor positive advanced breast cancer patients. Predictive biomarkers of everolimus efficacy have been investigated in primary breast cancer tissue without finding univocal results. The goal of this study was to investigate the mutational burden in the metastatic site of endocrine-resistant tumors treated with everolimus plus exemestane. Patients and Methods Mass Array Sequenom platform was used to analyse genetic status of 18 cancer-related genes in 25 archival tumor specimens from metastatic lesions and available primary matched breast cancer tissue of patients treated with everolimus and exemestane for advanced disease. An exploratory analysis of everolimus efficacy in terms of progression free survival benefit and single gene mutation was carried out. Results The overall detection rate of mutation was 30% and 38% from metastatic and primary breast cancer samples, respectively. AKT1E17K was the most frequent mutated gene. No primary breast cancer and matched relapse maintained the same mutation profile. Considering molecular pathways, the most of the genes belong to PI3K pathway (AKT1E17K, PI3KCAE545K, and KITG565R,S709F). In patients with detected mutations in breast and/or recurrence tissue the median PFS was 5,6 months while in the subgroup of patients with no mutations the median PFS was 7,5 months. Conclusions The mutational status of breast cancer recurrence allows the identification of some genes potentially correlating tumor response/resistance to everolimus. The most frequently mutated genes were involved in the PI3K/AKT/mTOR pathway highlighting that the deregulation of this pathway in the relapse plays a crucial role in the mechanisms of everolimus resistance/sensitivity. Owing to the small sample size and the retrospective nature of the study, these correlations need to be validated in a large prospective study.

CDK4/6 inhibitors in breast cancer therapy: Current practice and future opportunities.

Dysregulation of the cyclin dependent kinase pathway in luminal breast cancer creates a new therapeutic opportunity for estrogen receptor positive breast cancer. Initial pan-CDK inhibitors were associated with extensive toxicities but in recent years, the development of potent specific CDK inhibitors with favorable tolerability has driven renewed interests in this class of targeted therapies. Palbociclib, ribociclib and abemaciclib are specific CDK4/6 inhibitors that have been approved by the U.S. Food and Drug Administration for use in combination with endocrine therapy for women with advanced hormone receptor positive breast cancer. These three anticancer therapeutics were approved based on progression free survival benefit seen on phase III trials with the most common grade 3 treatment-related side effects being neutropenia, fatigue, nausea and diarrhea. Except for estrogen receptor positivity, no biomarkers predictive of response to CDK4/6 inhibitors have been identified to date. Based on mechanistic insights here described, CDK4/6 inhibitors are currently being explored in combination with other agents, including targeted therapies, immunotherapy and chemotherapy.

Effect of trastuzumab combined with endocrine therapy on hormone receptor and human epidermal growth factor receptor-2 positive advanced breast cancer

Objective To investigate the effect of trastuzumab combined with endocrine therapy on hormone receptor (HR) and human epidermal growth factor receptor-2 (HER-2) positive advanced breast cancer. Methods From January 2001 to March 2017, 88 patients with HR and HER-2 positive advanced breast cancer were selected.The patients were divided into two groups according to the random number method, with 44 cases in each group.All the patients were treated with routine chemotherapy, radiotherapy and biology therapy.The control group was treated with tamoxifen, and the observation group was treated with trastuzumab on the basis of the control group.All the patients were followed up for 6 months.The changes of serum E2 and quality of life were compared before and after intervention.The clinical effects of the two groups were compared. Results The serum E2 of the observation group was (15.3±0.5)pmol/L, which was lower than that before intervention [(65.4±2.0)pmol/L]and that of the control group after treatment [(36.9±1.9)pmol/L](t=70.109, 0.240, all P<0.05). After the intervention, the quality of life score of the observation group was (35.3±1.1)points, which was higher than that before intervention[(81.5±2.3)points]and that of the control group after treatment [(56.6±1.7)points](t=114.608, 66.530, all P<0.05). The effective rate of the observation group was 31.8%, which was higher than 9.1% of the control group (χ2=5.657, P<0.05). Conclusion Trastuzumab combined with endocrine maintenance therapy can effectively regulate the endocrine level of patients with HR and HER-2 positive advanced breast cancer, improve the quality of life and clinical therapeutic effect. Key words: Breast neoplasms; Receptors, estrogen; Receptor, epidermal growth factor; Trastuzumab

Correlation of expression of TK1 in plasma-derived exosomes with clinical response to CDK4/6 inhibitors in breast cancer.

12037Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) improve PFS in patients with hormone receptor positive (HR+) advanced breast cancer (1). In order to better characterize the respon...

Role of serum thymidine kinase-1 (TK1) activity in patients (pts) with hormone receptor positive (HR+) advanced breast cancer (ABC) treated with endocrine therapy (ET) in the EFECT trial.

12031Background: TK1 plays a critical role in DNA synthesis and cell proliferation. The DiviTum assay measures serum TK1 activity (sTKa), reflecting cancer cell proliferation. Recent studies sugges...

194 (PB-095) - Retrospective analysis of clinico-pathological factors affecting survival in endocrine resistant hormone receptor positive advanced breast cancer patients

194 (PB-095) - Retrospective analysis of clinico-pathological factors affecting survival in endocrine resistant hormone receptor positive advanced breast cancer patients

Abstract P4-12-08: Palbociclib in hormone receptor positive advanced breast cancer: A cost-utility analysis

Abstract Introduction The addition of palbociclib to letrozole improves progression free survival (PFS) and response rates compared to letrozole alone in the 1st line treatment of hormone receptor positive advanced breast cancer. However palbociclib increases toxicity (i.e. neutropenia) and costs more than $6,250 per month in Canada. This study assesses the cost-utility of palbociclib from the Canadian healthcare payer perspective. Methods To evaluate the cost-utility of palbociclib, a probabilistic discrete event simulation model was developed. The model was parameterized with data from the phase 2 and 3 PALOMA 1 and 2 trials and other sources. The incremental cost per quality-adjusted life-month (QALM) gained for palbociclib was calculated. A time horizon of 15 years was used in the base case with costs and effectiveness discounted 5% annually. The time to progression and death were derived from a Weibull and exponential distribution. Expected costs were based on Ontario fees and other sources. Probabilistic sensitivity analyses were conducted to account for parameter uncertainty. Results Compared to letrozole alone, the addition of palbociclib provided an additional 14.7 QALM at an incremental cost of $161,508. The resulting incremental cost-effectiveness ratio was $10,999 per QALM gained. Assuming a willingness to pay (WTP) of $4,167 per QALM, the addition of palbociclib was not cost-effective and the probability of palbociclib to be cost-effective was 0%. Cost-effectiveness acceptability curves derived from a probabilistic sensitivity analysis showed that at a WTP of $11,667 per QALM gained, the probability of palbociclib to be cost-effective was 50%. Conclusion Compared with letrozole alone, the addition of palbociclib is unlikely to be cost-effective for the treatment of advanced breast cancer from a Canadian healthcare perspective with its current price. While advanced breast cancer patients derive a meaningful clinical benefit from palbociclib, considerations should be given to increase the WTP threshold and reduce the drug pricing, to render this strategy more affordable. Citation Format: Raphael J, Helou J, Naimark DM. Palbociclib in hormone receptor positive advanced breast cancer: A cost-utility analysis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-12-08.