Overall survival in patients with hormone receptor-positive, HER2-negative, advanced or metastatic breast cancer treated with a cyclin-dependent kinase 4/6 inhibitor plus fulvestrant: a US Food and Drug Administration pooled analysis.

BACKGROUND: Cyclin-dependent kinase 4/6 inhibitors (CDKIs) are oral targeted agents approved for use in combination with endocrine therapy as first-line or second-line treatment of patients with hormone receptor-positive, HER2-negative, advanced or metastatic breast cancer. We previously reported the pooled analyses of progression-free survival in patients in specific clinicopathological subgroups, all of whom received consistent benefit from the addition of a CDKI to hormonal therapy. Here, we report the pooled overall survival results in patients treated with a CDKI and fulvestrant. METHODS: In this exploratory analysis, we pooled individual patient data from three phase 3 randomised trials of CDKI or placebo in combination with fulvestrant in patients with breast cancer submitted to the US Food and Drug Administration and approved before Aug 1, 2020, in support of marketing applications. All analysed patients were aged at least 18 years, had an Eastern Cooperative Oncology Group performance status of 0-1, had hormone receptor-positive, HER2-negative advanced or metastatic breast cancer, and received at least one dose of CDKI or placebo in combination with fulvestrant. The median overall survival was estimated using Kaplan-Meier methods, and hazard ratios (HRs) with corresponding 95% CIs were estimated using Cox regression models. Patients were analysed collectively, by number of previous lines of systemic endocrine therapy in any disease setting (first-line or endocrine naive vs second-line and later), and in various clinicopathological subgroups of interest. The estimated median overall survival was not reported by group when the pooled population included patients treated across lines of therapy because of potential patient heterogeneity. All results presented are considered exploratory and hypothesis generating. FINDINGS: Across the three pooled trials, 1960 patients were randomly assigned between Oct 7, 2013, and June 10, 2016 (12 patients were not treated and 1296 [66%] patients were randomly assigned to CDKI and 652 [33%] to placebo). In all treated patients (n=1948), the estimated HR for overall survival was 0·77 (95% CI 0·68-0·88), with a median follow-up of 43·7 months (IQR 37·8-47·7) and deaths in 935 (48%) of the 1948 patients. The difference in estimated median overall survival was 7·1 months, favouring CDKIs. In patients who received CDKIs or placebo in combination with fulvestrant as first-line systemic endocrine therapy (two trials; n=396), the estimated HR for overall survival was 0·74 (95% CI 0·52-1·07), with a median follow-up of 39·4 months (IQR 37·0-42·2). 123 (31%) of these patients died. The difference in estimated median overall survival could not be calculated because median overall survival was not estimable (95% CI 50·9-not estimable) in the CDKI group and was 45·7 months (95% CI 41·7-not estimable) in the placebo group. In patients who received CDKIs or placebo in combination with fulvestrant as second-line or later systemic endocrine therapy (three trials; n=1552), the estimated HR for overall survival was 0·77 (95% CI 0·67-0·89), with a median follow-up of 45·1 months (95% CI 39·2-48·5). 812 (52%) of these patients died. The difference in estimated median overall survival was 7·0 months, favouring CDKIs. INTERPRETATION: The addition of CDKIs to fulvestrant resulted in a consistent overall survival benefit in all pooled patients and within most clinicopathological subgroups of interest. These findings support the existing standard of care of CDKIs plus fulvestrant for the treatment of patients with hormone receptor-positive, HER2-negative, advanced breast cancer. FUNDING: None.

CDK4/6 inhibitor treatment for patients with hormone receptor-positive, HER2-negative, advanced or metastatic breast cancer: a US Food and Drug Administration pooled analysis.

BACKGROUND: Cyclin-dependent kinase 4/6 inhibitors (CDKIs) are indicated with endocrine therapy as first-line or second-line treatment for hormone receptor-positive, HER2-negative, advanced or metastatic breast cancer. We aimed to investigate the benefit of adding CDKIs to endocrine therapy in patients whose tumours might have differing degrees of endocrine sensitivity. METHODS: We pooled individual patient data from all phase 3 randomised breast cancer trials of CDKIs plus endocrine therapy submitted to the US Food and Drug Administration before Jan 1, 2019, in support of marketing applications. Our pooled analysis included all randomly assigned patients in these trials who received at least one dose of CDKI or placebo with endocrine therapy (an aromatase inhibitor [letrozole or anastrazole] or fulvestrant). We did prespecified subgroup analyses in patients with progesterone receptor-negative disease; patients with a disease-free interval of 12 months or less; patients with de-novo metastases, lobular histology, and bone-only disease; patients with visceral metastases; and patients aged up to 40 years. Patients who were not treated, who received tamoxifen as endocrine therapy, or who were treated with an aromatase inhibitor but who had received previous chemotherapy in the metastatic setting (not first-line) were excluded from our pooled analyses. All studies had a primary endpoint of investigator-assessed progression-free survival, defined as time from date of randomisation to the initial date of documented cancer progression or death, whichever occurred first. Median progression-free survival was estimated with Kaplan-Meier methods. Hazard ratios (HR) with 95% CIs for progression-free survival were estimated by means of Cox regression models. FINDINGS: The seven studies meeting this study's inclusion criteria were done between Feb 22, 2013, and Nov 3, 2017, with a median duration of follow-up of 19·7 months (IQR 15·9-25·9). 4200 patients were included in the pooled analysis, of whom 1320 received an aromatase inhibitor plus a CDKI, 932 received placebo plus an aromatase inhibitor, 1296 received fulvestrant plus a CDKI, and 652 received fulvestrant plus placebo. Across all seven pooled trials, the difference in estimated median progression-free survival was 8·8 months in favour of CDKI plus endocrine therapy over placebo plus endocrine therapy (range across the trials 6·8-13·3 months; HR 0·59, 95% CI 0·54-0·64). Progression-free survival results favoured the CDKI group in all prespecified clinicopathological subgroups analysed, with similar HRs to that for the broader intended-use population. In first-line aromatase inhibitor-treated patients (n=2252), the median progression-free survival in the CDKI plus aromatase inhibitor group was 28·0 months (95% CI 25·3-29·1) versus 14·9 months (14·0-16·7) in the placebo plus aromatase inhibitor group (difference 13·1 months; range across the trials 13·0-13·3 months; HR 0·55, 95% CI 0·49-0·62). In first-line fulvestrant-treated patients (n=396), the median progression-free survival was 18·6 months (95% CI 14·8-23·5) in the placebo plus fulvestrant group and not estimable (22·4 to not estimable) in the CDKI plus fulvestrant group (difference not estimable; HR 0·58, 95% CI 0·42-0·80). In the patients treated with fulvestrant in the second-line setting and beyond (n=1552), the difference in estimated median progression-free survival between the CDKI plus fulvestrant group and the placebo plus fulvestrant group was 6·9 months in favour of the CDKI group (range across the trials 5·5-7·3 months; HR 0·56, 95% CI 0·49-0·64). INTERPRETATION: Since the addition of CDKI to endocrine therapy seemed to benefit all clinicopathological subgroups of interest in this pooled analysis, further research is needed to identify patient subgroups for whom endocrine therapy alone might be appropriate for first-line or second-line treatment of hormone receptor-positive, HER2-negative metastatic breast cancer. FUNDING: None.

National Cancer Institute Breast Cancer Steering Committee Working Group Report on Meaningful and Appropriate End Points for Clinical Trials in Metastatic Breast Cancer.

PURPOSE: To provide evidence-based consensus recommendations on choice of end points for clinical trials in metastatic breast cancer, with a focus on biologic subtype and line of therapy. METHODS: The National Cancer Institute Breast Cancer Steering Committee convened a working group of breast medical oncologists, patient advocates, biostatisticians, and liaisons from the Food and Drug Administration to conduct a detailed curated systematic review of the literature, including original reports, reviews, and meta-analyses, to determine the current landscape of therapeutic options, recent clinical trial data, and natural history of four biologic subtypes of breast cancer. Ongoing clinical trials for metastatic breast cancer in each subtype also were reviewed from ClinicalTrials.gov for planned primary end points. External input was obtained from the pharmaceutic/biotechnology industry, real-world clinical data specialists, experts in quality of life and patient-reported outcomes, and combined metrics for assessing magnitude of clinical benefit. RESULTS: The literature search yielded 146 publications to inform the recommendations from the working group. CONCLUSION: Recommendations for appropriate end points for metastatic breast cancer clinical trials focus on biologic subtype and line of therapy and the magnitude of absolute and relative gains that would represent meaningful clinical benefit.

US Food and Drug Administration Pooled Analysis to Assess the Impact of Bone-Only Metastatic Breast Cancer on Clinical Trial Outcomes and Radiographic Assessments.

Purpose The outcome and proportion of patients with bone-only (BO) metastatic breast cancer (MBC) has not been well described. We sought to describe the differential outcomes of patients with BO MBC in clinical trials and explore whether there was a discrepancy in radiographic reads between investigator and blinded independent central review. Methods We pooled and analyzed data on 10,521 patients from 13 prospective trials submitted for MBC treatment in initial or supplemental New Drug or Biologics License Applications from 2005. Three subsets were evaluated: BO, bone with other metastases (BWO), and no bone metastases (NBM). Early discordance rate and late discordance rate were calculated from 3,733 and 2,813 patients subject to a blinded independent central review, respectively. Results Bone metastases were identified in 49% (range: 42% to 73%) of patients across trials. BO disease was present in 12.5% (range: 4% to 26%), dependent on subtype. Investigator-assessed progression-free survival (PFS) and overall survival (OS) for the pooled trials demonstrated improved outcomes for the BO subgroup compared with other subgroups (BO v BWO PFS hazard ratio [HR], 0.64; 95% CI, 0.591 to 0.696; BO v NBM PFS HR, 0.70; 95% CI, 0.65 to 0.76; BO v BWO OS HR, 0.56; 95% CI, 0.50 to 0.61; BO v NBM OS HR, 0.68; 95% CI, 0.61 to 0.76). The BO subgroup has a higher early discordance rate and lower late discordance rate than the BWO and NBM subgroups. Conclusion To our knowledge, this review is the largest analysis to date of the BO subgroup of MBC and suggests this subgroup may have a distinct natural history. There also seems to be a difference in how the local investigators assessed progression events in the BO subgroup when compared with the other two groups.

Inflammatory breast cancer: dynamic contrast-enhanced MR in patients receiving bevacizumab--initial experience.

PURPOSE: To retrospectively compare three dynamic contrast material-enhanced magnetic resonance (MR) imaging (dynamic MR imaging) analytic methods to determine the parameter or combination of parameters most strongly associated with changes in tumor microvasculature during treatment with bevacizumab alone and bevacizumab plus chemotherapy in patients with inflammatory or locally advanced breast cancer. MATERIALS AND METHODS: This study was conducted in accordance with the institutional review board of the National Cancer Institute and was compliant with the Privacy Act of 1974. Informed consent was obtained from all patients. Patients with inflammatory or locally advanced breast cancer were treated with one cycle of bevacizumab alone (cycle 1) followed by six cycles of combination bevacizumab and chemotherapy (cycles 2-7). Serial dynamic MR images were obtained, and the kinetic parameters measured by using three dynamic analytic MR methods (heuristic, Brix, and general kinetic models) and two region-of-interest strategies were compared by using two-sided statistical tests. A P value of .01 was required for significance. RESULTS: In 19 patients, with use of a whole-tumor region of interest, the authors observed a significant decrease in the median values of three parameters measured from baseline to cycle 1: forward transfer rate constant (Ktrans) (-34% relative change, P=.003), backflow compartmental rate constant extravascular and extracellular to plasma (Kep) (-15% relative change, P<.001), and integrated area under the gadolinium concentration curve (IAUGC) at 180 seconds (-23% relative change, P=.009). A trend toward differences in the heuristic slope of the washout curve between responders and nonresponders to therapy was observed after cycle 1 (bevacizumab alone, P=.02). The median relative change in slope of the wash-in curve from baseline to cycle 4 was significantly different between responders and nonresponders (P=.009). CONCLUSION: The dynamic contrast-enhanced MR parameters Ktrans, Kep, and IAUGC at 180 seconds appear to have the strongest association with early physiologic response to bevacizumab. Clinical trial registration no. NCT00016549

Phase II clinical trial of ixabepilone (BMS-247550), an epothilone B analog, in metastatic and locally advanced breast cancer.

PURPOSE: Ixabepilone (BMS-247550) is an epothilone B analog that stabilizes microtubules and has antitumor activity in taxane-refractory patients in phase I studies. In a phase II trial, we evaluated the efficacy and safety of ixabepilone in women with metastatic and locally advanced breast cancer. PATIENTS AND METHODS: Breast cancer patients with measurable disease who had paclitaxel and/or docetaxel as prior neoadjuvant, adjuvant, or metastatic therapy were treated with ixabepilone at 6 mg/m2/d intravenously on days 1 through 5 every 3 weeks. Levels of glutamate (glu) -terminated and acetylated alpha-tubulin, markers of microtubule stabilization, were detected by Western blot and by immunohistochemistry in a subset of matched pre- and post-treatment tumor biopsies. RESULTS: Thirty-seven patients received 153 cycles of ixabepilone. The best responses were a complete response in one patient (3%), partial responses in seven patients (19%), and stable disease in 13 patients (35%). Grade 3 and 4 toxicities included neutropenia (35%), febrile neutropenia (14%), fatigue (14%), diarrhea (11%), nausea/vomiting (5%), myalgia/arthralgia (3%), and sensory neuropathy (3%). Two patients were removed from study because of prolonged grade 2 or 3 neurotoxicity, and three patients were removed from study for other grade 3 and 4 nonhematologic toxicities. Compared with baseline levels, levels of both glu-terminated and acetylated alpha-tubulin were increased in tumor biopsies performed after ixabepilone therapy. CONCLUSION: An objective response was seen in 22% of the patients in a population who had been previously treated with a taxane. Sensory neuropathy was mild with grade 3 neurotoxicity rarely seen. Microtubule stabilization occurred in tumor biopsies after treatment with ixabepilone.