Systematic review and meta-analysis of post-progression outcomes in ER+/HER2- metastatic breast cancer after CDK4/6 inhibitors within randomized clinical trials

Background

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and endocrine therapy (ET) deeply transformed the treatment landscape of hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2−) advanced breast cancer. Randomized clinical trials suggest that second progression-free survival (PFS2) was not compromised and time to subsequent chemotherapy (TTC) may be delayed. We carried out a meta-analysis to assess the benefit on PFS2 and on delaying the TTC.

Methods

We conducted a systematic literature search of randomized clinical trials with CDK4/6 inhibitors and ET reporting PFS2 or TTC of HR+/HER2− pre- or postmenopausal metastatic breast cancer. We also reviewed abstracts and presentations from all major conference proceedings. We calculated the pooled hazard ratios (HR) for PFS2 and TTC using random-effects models with 95% confidence intervals (CI). I² was used to quantify heterogeneity between results of the studies.

Results

Eight studies (MONALEESA-2/3/7, MONARCH-2/3, PALOMA-1/2/3) were included in this analysis (N = 4580 patients). PFS2 benefit was observed in patients who received CDK4/6 inhibitors plus ET (pooled HR = 0.68, 95% CI = 0.62-0.74, I² = 0%) and also a delay in subsequent TTC (pooled HR = 0.65, 95% CI = 0.60-0.71, I² = 0%). A benefit in terms of PFS (pooled HR = 0.55, 95% CI = 0.51-0.59, I² = 0%) and overall survival (pooled HR = 0.76, 95% CI = 0.69-0.84, I² = 0%) was also observed.

Conclusions

CDK4/6 inhibitors plus ET compared with ET alone improve PFS2 and TTC. The delay of chemotherapy may postpone the start of a more toxic treatment option, delaying related toxicities and potentially maintaining a better quality of life for patients, for a longer time. The benefit in PFS2 may postpone the onset of endocrine resistance and help further validate this treatment approach.

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Eight RCTs (MONALEESA-2/3/7, MONARCH-2/3, PALOMA-1/2/3) were included in this analysis on pooled HR for PFS2 and TTC.

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Patients who received CDK4/6 inhibitors plus ET had a clear PFS2 benefit and a delay in subsequent TTC.

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CDK4/6 inhibitors plus ET compared with ET alone improve PFS2 and TTC.

A clinical validation study of MammaPrint in hormone receptor-positive breast cancer from the Austrian Breast and Colorectal Cancer Study Group 8 (ABCSG-8) biomarker cohort

Background

MammaPrint is a prognostic assay based on gene expression in tumors from patients with early breast cancer. MammaPrint has been extensively validated and Food and Drug Administration cleared in fresh and formalin-fixed and paraffin-embedded (FFPE) tissue. We aimed to assess its prognostic performance in the biomarker cohort of the Austrian Breast and Colorectal Cancer Study Group 8 (ABCSG-8) patient population, and to obtain a higher level of evidence with regard to its clinical validity after RNA extraction from FFPE biobank tissue.

Patients and methods

A prespecified retrospective analysis to test the prognostic performance of the MammaPrint test to predict distant recurrence-free survival at 5 and 10 years as primary end point was carried out. MammaPrint risk, clinicopathological factors (after central pathological review), and clinical risk (using a modified version of Adjuvant! Online) were evaluated by Cox regression analyses.

Results

From 1347 available samples, 607 (45%) failed quality control after RNA extraction. In total, 658 (49%) patients were included in survival analyses: MammaPrint low risk versus high risk is a significant prognostic factor for distant recurrence-free survival at 5 years (94.0% versus 91.6%) with a significant risk reduction of 6.5% at 10 years (log-rank P value = 0.017, low risk 91.3% versus high risk 84.8%). The multivariable models suggest that hazard ratio (HR) is primarily driven by tumor stage (5-year HR 3.89; confidence interval 1.97-7.71) and nodal status (5-year HR 1.73; confidence interval 0.91-3.21). After adjustment for clinical risk groups, MammaPrint HRs remain stable with values just below 2.0 after the first 3 years.

Conclusions

The MammaPrint test showed significant prognostic performance at 5 and 10 years of follow-up. In the particular cohort of ABCSG-8, the statistical independence from clinically assessed covariates remains unclear, and no conclusions concerning the clinical validity of the test can be drawn.

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MammaPrint is a prognostic assay based on gene expression in tumors from patients with early breast cancer.

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MammaPrint has been extensively and successfully validated- but mostly in fresh tissue.

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We aimed to assess its prognostic performance in FFPE tissue from the ABCSG 8 biomarker cohort.

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The MammaPrint test showed significant prognostic performance at 5 and 10 years of follow-up.

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The statistical independence from clinically assessed covariates is unclear- the clinical validity in ABCSG 8 uncertain.

Adjuvant endocrine treatment for estrogen receptor (ER)-positive/HER2-negative breast cancer

Approximately 70% of women with breast cancer worldwide receive a diagnosis of ER-positive/ HER2-negative disease. Recurrence-free survival of the node-negative population of these women is approximately 85%, and most are treated with endocrine chemotherapy. Endocrine treatment for ERpositive/HER2-negative early breast cancer is a major treatment strategy. Breast cancer clinicians have gained much experience with this issue, but new data regarding adjuvant endocrine therapy have recently been accumulated. In the integrated analyses of the Suppression of Ovarian Function Trial (SOFT) and Tamoxifen and Exemestane Trial (TEXT) trials, the addition of ovarian function suppression (OFS) to tamoxifen showed a significant improvement in both 8-year disease-free survival [hazard ratio (HR) 0.76, 95% confidence interval (CI): 0.62-0.93] and overall survival (HR 0.67, 95% CI: 0.48-0.92) compared with tamoxifen alone for premenopausal patients with breast cancer, with the assumption of 5 years as an appropriate duration for OFS. The ATLAS trial showed that, compared with 5 years of tamoxifen, 10 years of tamoxifen provided further benefit to women with HR-positive early breast cancer in recurrence [5-9 years: rate ratio (RR) 0.90, 95% CI: 0.79-1.07; ≥10 years: RR 0.75, 95% CI: 0.62-0.90; and all years: log-rank P=0.002] and breast cancer mortality (5-9 years: RR 0.97, 95% CI: 0.79-1.18; ≥10 years: RR 0.71, 95% CI: 0.58-0.88; and all years: log-rank P=0.01), particularly after reaching 10 years, which is considered a "carry over" benefit. In this review, adjuvant endocrine treatment for ER-positive/HER2-negative early breast cancer is discussed. Particular areas of focus are premenopausal patients, especially regarding the addition of OFS, postmenopausal patients, the duration of adjuvant endocrine therapy, the treatment implications of multigene expression assays, and adjuvant endocrine therapy for ductal carcinoma in situ. Some of this evidence supports the clinical management of breast cancer patients as well as clinical studies in the future.

Fibroblast growth factor receptor-1 protein expression is associated with prognosis in estrogen receptor-positive/human epidermal growth factor receptor-2-negative primary breast cancer

Recently, research into the development of new targeted therapies has focused on specific genetic alterations to create advanced, more personalized treatment. One of the target genes, fibroblast growth factor receptor‐1 (FGFR1), has been reported to be amplified in estrogen receptor (ER)‐positive subtype breast cancer, and is considered one possible mechanism of endocrine resistance through cross‐talk between ER and growth factor receptor signaling. We performed a comprehensive analysis of FGFR1 at the levels of gene copy number, transcript and protein expression, and examined the relationships between FGFR1 status and clinicopathological parameters, including prognosis in 307 ER‐positive/HER2‐negative primary breast cancer patients treated with standard care at our institute. Most notably, a high level of FGFR1 protein expression was observed in 85 patients (27.7%), and was positively associated with invasive tumor size (P = 0.039). Furthermore, univariate analysis revealed that high FGFR1 protein expression was significantly correlated with poor relapse‐free survival rate (P = 0.0019, HR: 2.63, 95% confidence interval: 1.17–5.98), and showed a tendency towards an increase in recurrent events if the observation period extended beyond the 5 years of the standard endocrine treatment term. FGFR1 gain/amplification was found in 43 (14.0%) patients, which was only associated with higher nuclear grade (P = 0.010). No correlation was found between FGFR1 mRNA expression levels and any clinicopathological factors. Overall, the level of FGFR1 protein expression may be a biomarker of ER‐positive/HER2‐negative primary breast cancer with possible resistance to standard treatment, and may be a useful tool to identify more specific patients who would benefit from FGFR‐1 targeted therapy.