Treatment effect of palbociclib plus endocrine therapy by prognostic and intrinsic subtype and biomarker analysis in patients with bone-only disease: a joint analysis of PALOMA-2 and PALOMA-3 clinical trials.

PURPOSE: This analysis evaluated the relationship between treatment-free interval (TFI, in PALOMA-2)/disease-free interval (DFI, in PALOMA-3) and progression-free survival (PFS) and overall survival (OS, in PALOMA-3), treatment effect in patients with bone-only disease, and whether intrinsic subtype affects PFS in patients receiving palbociclib. METHODS: Data were from phase 3, randomized PALOMA-2 and PALOMA-3 clinical studies of hormone receptor‒positive/human epidermal growth factor receptor 2‒negative (HR+ /HER2-) advanced breast cancer (ABC) patients receiving endocrine therapy plus palbociclib or placebo. Subpopulation treatment effect pattern plot (STEPP) analysis evaluated the association between DFI and PFS and OS. PFS by luminal subtype and cyclin-dependent kinase (CDK) 4/6 or endocrine pathway gene expression levels were evaluated in patients with bone-only disease; median PFS and OS were estimated by the Kaplan-Meier method. RESULTS: Median durations of TFI were 37.1 and 30.9 months (PALOMA-2) and DFI were 49.2 and 52.0 months (PALOMA-3) in the palbociclib and placebo groups, respectively. Among the PALOMA-2 biomarker population (n = 454), 23% had bone-only disease; median PFS was longer with palbociclib versus placebo (31.3 vs 11.2 months; hazard ratio, 0.41; 95% CI 0.25‒0.69). The interaction effect of bone-only versus visceral disease subgroups on median PFS with palbociclib was not significant (P = 0.262). Among the PALOMA-3 biomarker population (n = 302), 27% had bone-only disease. STEPP analyses showed that palbociclib PFS benefit was not affected by DFI, and that palbociclib OS effect may be smaller in patients with short DFIs. Among patients who provided metastatic tumor tissues (n = 142), regardless of luminal A (hazard ratio, 0.23; 95% CI 0.11‒0.47; P = 0.0000158) or luminal B (hazard ratio, 0.26; 95% CI 0.12‒0.56; P = 0.000269) subtype, palbociclib improved PFS versus placebo. CONCLUSIONS: These findings support palbociclib plus endocrine therapy as standard of care for HR+ /HER2- ABC patients, regardless of baseline TFI/DFI or intrinsic molecular subtype, including patients with bone-only disease. TRIAL REGISTRATION: Pfizer (clinicaltrials.gov:NCT01740427, NCT01942135).

Cyclin E1 Expression and Palbociclib Efficacy in Previously Treated Hormone Receptor-Positive Metastatic Breast Cancer.

PURPOSE: A large-panel gene expression analysis was conducted to identify biomarkers associated with the effectiveness of adding palbociclib to fulvestrant. METHODS: The PALOMA-3 ( ClinicalTrials.gov identifier: NCT01942135) trial randomly assigned 521 endocrine-pretreated patients with metastatic breast cancer to receive palbociclib plus fulvestrant or placebo plus fulvestrant. Primary analysis was first conducted on 10 genes on the basis of pathway biology and evidence from previous studies followed by a systematic panel-wide search among 2,534 cancer-related genes. The association of gene expression with the effect of palbociclib on progression-free survival (PFS) was evaluated using Cox proportional hazards regression analysis, with gene expression as a continuous variable or dichotomized by median. An independent breast cancer cohort from the Preoperative Palbociclib (POP) Clinical Trial ( ClinicalTrials.gov identifier: NCT02008734) was used for validation, in 61 patients with primary breast cancer treated with 2 weeks of palbociclib. RESULTS: In the PALOMA-3 trial, 302 patients had tumor tissue analyzed (palbociclib arm, 194 patients; placebo arm, 108 patients). Palbociclib efficacy was lower in patients with high versus low cyclin E1 (CCNE1) mRNA expression (median PFS: palbociclib arm, 7.6 v 14.1 months; placebo arm, 4.0 v 4.8 months, respectively; interaction P unadjusted = .00238; false discovery rate-adjusted P = .0238). CCNE1 mRNA was more predictive in metastatic than in archival primary biopsy tissue samples. No significant interaction was found between treatment and expression levels of CDK4, CDK6, cyclin D1, and RB1. Palbociclib was efficacious in both luminal A and luminal B tumors. High CCNE1 mRNA expression was associated with poor antiproliferative activity of palbociclib in the POP trial (P = .005). CONCLUSION: Addition of palbociclib to fulvestrant demonstrated efficacy in all biomarker groups, although high CCNE1 mRNA expression was associated with relative resistance to palbociclib.

Overall Survival with Palbociclib and Fulvestrant in Advanced Breast Cancer.

BACKGROUND: The cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor palbociclib, in combination with fulvestrant therapy, prolongs progression-free survival among patients with hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. We report the results of a prespecified analysis of overall survival. METHODS: We randomly assigned patients with hormone-receptor-positive, HER2-negative advanced breast cancer who had progression or relapse during previous endocrine therapy to receive palbociclib plus fulvestrant or placebo plus fulvestrant. We analyzed overall survival; the effect of palbociclib according to the prespecified stratification factors of presence or absence of sensitivity to endocrine therapy, presence or absence of visceral metastatic disease, and menopausal status; the efficacy of subsequent therapies after disease progression; and safety. RESULTS: Among 521 patients who underwent randomization, the median overall survival was 34.9 months (95% confidence interval [CI], 28.8 to 40.0) in the palbociclib-fulvestrant group and 28.0 months (95% CI, 23.6 to 34.6) in the placebo-fulvestrant group (hazard ratio for death, 0.81; 95% CI, 0.64 to 1.03; P=0.09; absolute difference, 6.9 months). CDK4/6 inhibitor treatment after the completion of the trial regimen occurred in 16% of the patients in the placebo-fulvestrant group. Among 410 patients with sensitivity to previous endocrine therapy, the median overall survival was 39.7 months (95% CI, 34.8 to 45.7) in the palbociclib-fulvestrant group and 29.7 months (95% CI, 23.8 to 37.9) in the placebo-fulvestrant group (hazard ratio, 0.72; 95% CI, 0.55 to 0.94; absolute difference, 10.0 months). The median duration of subsequent therapy was similar in the two groups, and the median time to the receipt of chemotherapy was 17.6 months in the palbociclib-fulvestrant group, as compared with 8.8 months in the placebo-fulvestrant group (hazard ratio, 0.58; 95% CI, 0.47 to 0.73; P<0.001). No new safety signals were observed with 44.8 months of follow-up. CONCLUSIONS: Among patients with hormone-receptor-positive, HER2-negative advanced breast cancer who had sensitivity to previous endocrine therapy, treatment with palbociclib-fulvestrant resulted in longer overall survival than treatment with placebo-fulvestrant. The differences in overall survival in the entire trial group were not significant. (Funded by Pfizer; PALOMA-3 ClinicalTrials.gov number, NCT01942135 .).

Predictors of prolonged benefit from palbociclib plus fulvestrant in women with endocrine-resistant hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer in PALOMA-3.

BACKGROUND: The addition of palbociclib to fulvestrant improved clinical outcomes over placebo-fulvestrant in endocrine-pretreated metastatic breast cancer (MBC) patients in PALOMA-3. Here, we examined factors predictive of long-term benefit. METHODS: Premenopausal-peri/postmenopausal patients with endocrine-resistant, hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative MBC were randomised 2:1 to fulvestrant (500 mg) and either palbociclib (125 mg/d; 3/1 schedule; n = 347) or placebo (n = 174). Baseline characteristics, mutation status and HR expression levels were compared in patients with and without prolonged benefit (treatment duration ≥18 months). RESULTS: By August 2016, 100 patients (29%) on palbociclib-fulvestrant and 26 (15%) on placebo-fulvestrant demonstrated prolonged benefit, with long-term responders in both arms sharing common clinical characteristics. They usually had less disease burden at baseline versus those treated <18 months, such as having one disease site (40% vs 29% on palbociclib-fulvestrant and 69% vs 29% on placebo-fulvestrant), bone-only disease (32% vs 22% and 46% vs 17%) and were less heavily pretreated (69% vs 56% and 73% vs 60% had ≤2 prior therapies). Baseline tumour ESR1 and PIK3CA mutation rates were lower among long-term responders in both arms; median oestrogen receptor H-scores were similar, whereas progesterone receptor H-scores were higher among long-term responders. CONCLUSIONS: This exploratory analysis demonstrates that some patients with endocrine-resistant MBC derive significant and prolonged benefit when treated with palbociclib-fulvestrant, with fewer patients experiencing similar efficacy with placebo-fulvestrant. The current analysis did not identify specific molecular or clinical factors prognostic of long-term benefit with palbociclib-fulvestrant (ClinicalTrials.gov, NCT01942135).

PALOMA-3: Phase III Trial of Fulvestrant With or Without Palbociclib in Premenopausal and Postmenopausal Women With Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer That Progressed on Prior Endocrine Therapy-Safety and Efficacy in Asian Patients.

PURPOSE: To assess efficacy and safety of palbociclib plus fulvestrant in Asians with endocrine therapy-resistant metastatic breast cancer. PATIENTS AND METHODS: The Palbociclib Ongoing Trials in the Management of Breast Cancer 3 (PALOMA-3) trial, a double-blind phase III study, included 521 patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer with disease progression on endocrine therapy. Patient-reported outcomes (PROs) were assessed on study treatment and at the end of treatment. RESULTS: This preplanned subgroup analysis of the PALOMA-3 study included premenopausal and postmenopausal Asians taking palbociclib plus fulvestrant (n = 71) or placebo plus fulvestrant (n = 31). Palbociclib plus fulvestrant improved progression-free survival (PFS) compared with fulvestrant alone. Median PFS was not reached with palbociclib plus fulvestrant (95% CI, 9.2 months to not reached) but was 5.8 months with placebo plus fulvestrant (95% CI, 3.5 to 9.2 months; hazard ratio, 0.485; 95% CI, 0.270 to 0.869; P = .0065). The most common all-cause grade 3 or 4 adverse events in the palbociclib arm were neutropenia (92%) and leukopenia (29%); febrile neutropenia occurred in 4.1% of patients. Within-patient mean trough concentration comparisons across subgroups indicated similar palbociclib exposure between Asians and non-Asians. Global quality of life was maintained; no statistically significant changes from baseline were observed for patient-reported outcome scores with palbociclib plus fulvestrant. CONCLUSION: This is the first report, to our knowledge, showing that palbociclib plus fulvestrant improves PFS in asian patients. Palbociclib plus fulvestrant was well tolerated in this study.

Palbociclib in Hormone-Receptor-Positive Advanced Breast Cancer.

BACKGROUND: Growth of hormone-receptor-positive breast cancer is dependent on cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), which promote progression from the G1 phase to the S phase of the cell cycle. We assessed the efficacy of palbociclib (an inhibitor of CDK4 and CDK6) and fulvestrant in advanced breast cancer. METHODS: This phase 3 study involved 521 patients with advanced hormone-receptor-positive, human epidermal growth factor receptor 2-negative breast cancer that had relapsed or progressed during prior endocrine therapy. We randomly assigned patients in a 2:1 ratio to receive palbociclib and fulvestrant or placebo and fulvestrant. Premenopausal or perimenopausal women also received goserelin. The primary end point was investigator-assessed progression-free survival. Secondary end points included overall survival, objective response, rate of clinical benefit, patient-reported outcomes, and safety. A preplanned interim analysis was performed by an independent data and safety monitoring committee after 195 events of disease progression or death had occurred. RESULTS: The median progression-free survival was 9.2 months (95% confidence interval [CI], 7.5 to not estimable) with palbociclib-fulvestrant and 3.8 months (95% CI, 3.5 to 5.5) with placebo-fulvestrant (hazard ratio for disease progression or death, 0.42; 95% CI, 0.32 to 0.56; P<0.001). The most common grade 3 or 4 adverse events in the palbociclib-fulvestrant group were neutropenia (62.0%, vs. 0.6% in the placebo-fulvestrant group), leukopenia (25.2% vs. 0.6%), anemia (2.6% vs. 1.7%), thrombocytopenia (2.3% vs. 0%), and fatigue (2.0% vs. 1.2%). Febrile neutropenia was reported in 0.6% of palbociclib-treated patients and 0.6% of placebo-treated patients. The rate of discontinuation due to adverse events was 2.6% with palbociclib and 1.7% with placebo. CONCLUSIONS: Among patients with hormone-receptor-positive metastatic breast cancer who had progression of disease during prior endocrine therapy, palbociclib combined with fulvestrant resulted in longer progression-free survival than fulvestrant alone. (Funded by Pfizer; PALOMA3 ClinicalTrials.gov number, NCT01942135.).

Gene expression profiling of sequential metastatic biopsies for biomarker discovery in breast cancer.

The feasibility of longitudinal metastatic biopsies for gene expression profiling in breast cancer is unexplored. Dynamic changes in gene expression can potentially predict efficacy of targeted cancer drugs. Patients enrolled in a phase III trial of metastatic breast cancer with docetaxel monotherapy versus combination of docetaxel + sunitinib were offered to participate in a translational substudy comprising longitudinal fine needle aspiration biopsies and Positron Emission Tomography imaging before (T1) and two weeks after start of treatment (T2). Aspirated tumor material was used for microarray analysis, and treatment-induced changes (T2 versus T1) in gene expression and standardized uptake values (SUV) were investigated and correlated to clinical outcome measures. Gene expression profiling yielded high-quality data at both time points in 14/18 patients. Unsupervised clustering revealed specific patterns of changes caused by monotherapy vs. combination therapy (p = 0.021, Fisher's exact test). A therapy-induced reduction of known proliferation and hypoxia metagene scores was prominent in the combination arm. Changes in a previously reported hypoxia metagene score were strongly correlated to the objective responses seen by conventional radiology assessments after 6 weeks in the combination arm, Spearman's ρ = 1 (p = 0.017) but not in monotherapy, ρ = -0.029 (p = 1). Similarly, the Predictor Analysis of Microarrays 50 (PAM50) proliferation metagene correlated to tumor changes merely in the combination arm at 6 and 12 weeks (ρ = 0.900, p = 0.083 and ρ = 1, p = 0.017 respectively). Reductions in mean SUV were a reliable early predictor of objective response in monotherapy, ρ = 0.833 (p = 0.008), but not in the combination arm ρ = -0.029 (p = 1). Gene expression profiling of longitudinal metastatic aspiration biopsies was feasible, demonstrated biological validity and provided predictive information.

An exploratory study of sunitinib in combination with docetaxel and trastuzumab as first-line therapy for HER2-positive metastatic breast cancer.

BACKGROUND: This exploratory study assessed the safety, pharmacokinetics, and antitumor activity of sunitinib combined with docetaxel and trastuzumab. METHODS: Patients with unresectable, locally recurrent or metastatic human epidermal growth factor receptor 2 (HER2)+ breast cancer received sunitinib plus docetaxel and trastuzumab. Sunitinib was administered at 37.5 mg/day for 2 weeks on treatment followed by 1 week off (Schedule 2/1). The primary endpoint was safety; secondary endpoints included pharmacokinetics and antitumor activity. RESULTS: Twenty-six patients enrolled; 24 received at least one dose of sunitinib plus docetaxel and trastuzumab, and one patient received one dose of docetaxel and trastuzumab only. These 25 treated patients were evaluable for safety. Twenty-three patients discontinued the study, primarily due to disease progression. The planned dose of sunitinib was maintained in 10 patients and reduced at least once to 25 mg/day in 14 patients. The most common grade 3/4 non-hematologic adverse events were fatigue/asthenia (28%), diarrhea (16%), stomatitis (12%), vomiting (8%) and dyspnea (8%). Neutropenia was reported in all 24 evaluable patients; most events were grade 4. Three grade 1-3 cardiac adverse events occurred. Sunitinib and docetaxel levels were consistent with known single-agent levels, suggesting that there were no clinically relevant drug-drug interactions. Of 22 evaluable patients, 16 (73%) experienced an objective response (all confirmed partial responses). CONCLUSIONS: Sunitinib combined with docetaxel and trastuzumab had an acceptable toxicity profile and showed preliminary antitumor activity as first-line treatment for metastatic HER2+ breast cancer.

Incidence-based cost-of-illness model for metastatic breast cancer in the United States.

OBJECTIVES: This study aims to estimate the annual U.S. societal costs associated with treatment of metastatic breast cancer (MBC) patients using an incidence-based cost-of-illness (COI) framework. METHODS: An incidence-based COI model was constructed in which MBC patients were simulated from diagnosis through active treatment, palliative care, and death over 5 years. Key model parameters included: annual incidence of breast cancer in the metastatic stage, utilization of cancer therapies and other medical care resources, treatment-related adverse events, unit costs, work days missed by patient and caregiver, and wage rates. Overall survival was based on SEER data and costs were assigned to living patients monthly, according to their disease management phase. The outcomes measures were total discounted societal costs, cost/year, and cost/patient-year. RESULTS: The annual incidence of MBC in the United States in 2007 was estimated to be 49,674 patients (de novo and progressed from earlier stages). The total discounted cost to society attributable to MBC was $12.2 billion for the incident cohort, or $98,571 per patient-year. The 5-year direct medical cost of this incident cohort was $9.3 billion, or $75,415 per patient-year. Treatment-related costs (active treatment, toxicity management, and medical follow-up) contributed 44 percent of MBC expenditure, followed by palliative/best supportive care costs (31 percent). Lost productivity accounted for approximately 21 percent of the total cost ($2.6 billion over 5 years or $21,153 per patient-year). CONCLUSIONS: The societal burden of MBC in the United States is substantial. Earlier detection and effective treatment could lead to a significant decrease in costs while improving overall disease prognosis.

Clinical and pharmacokinetic study of sunitinib and docetaxel in women with advanced breast cancer.

BACKGROUND: This exploratory study examined the pharmacokinetics, safety, and antitumor activity of sunitinib plus docetaxel in patients with HER-2-negative advanced breast cancer. PATIENTS AND METHODS: Patients with HER-2-negative disease who had received prior adjuvant anthracycline-based therapy received docetaxel (75 mg/m(2)) on day 1 of each 3-week cycle followed by sunitinib (37.5 mg/day for 2 weeks on Schedule 2/1) starting on day 2 (day 3 on cycle 2). RESULTS: Twenty-two patients were enrolled. No clinically significant drug-drug interactions were observed. The most common non-hematologic AE (any grade) was fatigue/asthenia. Grade 4 neutropenia occurred in 20/22 patients (91%; n = 7 had neutropenic fever). The safety profile was similar to each agent given individually. 14/19 (73.7%) evaluable patients had a PR and 5/19 (26.3%) had SD. CONCLUSIONS: Sunitinib plus docetaxel on Schedule 2/1 did not result in any clinically significant drug-drug interactions. This combination was manageable and exhibited antitumor activity.

First-line treatment of advanced breast cancer with sunitinib in combination with docetaxel versus docetaxel alone: results of a prospective, randomized phase III study.

PURPOSE: To investigate whether sunitinib plus docetaxel improves clinical outcomes for patients with human epidermal growth factor receptor 2 (HER2)/neu-negative advanced breast cancer (ABC) versus docetaxel alone. PATIENTS AND METHODS: In this phase III study, patients were randomly assigned to open-label combination therapy (sunitinib 37.5 mg/d, days 2 to 15 every 3 weeks; and docetaxel 75 mg/m(2), day 1 every 3 weeks) or monotherapy (docetaxel 100 mg/m(2) every 3 weeks). Progression-free survival (PFS) was the primary end point. RESULTS: Two hundred ninety-six patients were randomly assigned to combination therapy, and 297 patients were assigned to monotherapy. Median PFS times were 8.6 and 8.3 months with combination therapy and monotherapy, respectively (hazard ratio, 0.92; one-sided P = .265). The objective response rate (ORR) was significantly higher with the combination (55%) than with monotherapy (42%; one-sided P = .001). Duration of response was similar in both arms (7.5 months with the combination v 7.2 months with monotherapy). Median overall survival (OS) times were 24.8 and 25.5 months with combination therapy and monotherapy, respectively (one-sided P = .904). There were 107 deaths with the combination and 91 deaths with monotherapy. The frequency of common adverse events (AEs) was higher with the combination, as were treatment discontinuations caused by AEs. CONCLUSION: The combination of sunitinib plus docetaxel improved ORR but did not prolong either PFS or OS compared with docetaxel alone when given to an unselected HER2/neu-negative cohort as first-line treatment for ABC. Sunitinib combination therapy may also have resulted in AEs that yield an unfavorable risk-benefit ratio. The sunitinib-docetaxel regimen evaluated in this study is not recommended for further use in ABC.