Dual- versus single-agent HER2 inhibition and incidence of intracranial metastatic disease: a systematic review and meta-analysis

A hybrid [18F]fluoropivalate PET-multiparametric MRI to detect and characterise brain tumour metastases based on a permissive environment for monocarboxylate transport

The incidence of Intracranial Metastatic Disease (IMD) continues to increase in part due to improvements in systemic therapy resulting in durable control of extra-cranial disease (ECD). Contrast-enhanced Magnetic Resonance Imaging (CE-MRI) is the preferred method for imaging IMD, but has limitations particularly in follow-up surveillance scans to optimise patient care. We investigate a new diagnostic approach of hybrid ([18]F]fluoropivalate (FPIA) Positron Emission Tomography-multiparametric MRI (PET-mpMRI), in 12 treatment-naïve and 10 stereotactic radiosurgery (SRS)-treated patients (± combination therapy within 4-8 weeks). High FPIA uptake was seen in all IMD compared to contralateral white matter, regardless of ECD tumour-of-origin (p = 0.0001) and FPIA-PET volumes extended beyond CE-MRI volumes in treatment-naïve but not SRS-treated tumours. Patients with maximum PET Standardised Uptake Value, (SUVmax) ≥ 2.0 showed particularly short overall-survival (median 4 v 15 months, p = 0.0136), while CE-MRI was uninformative regarding outcome; a PET-mpMRI grade-measure also provided non-invasive prediction of overall-survival, warranting larger studies of PET-mpMRI. Independent metabolomics analyses were consistent with shared adaptation of IMD to utilise or accumulate monocarboxylates and acylcarnitines, respectively, providing a common phenotypic basis to FPIA-PET. Reprogrammed monocarboxylate metabolism-related FPIA-PET provides new insights into annotating IMD, to be expounded in future opportunities for therapy decisions for the growing number of cancer patients with IMD [Trial registration reference: Clinicaltrials.gov NCT04807582; 3rd November 2021, retrospectively registered].

Association of Brain Metastases With Survival in Patients With Limited or Stable Extracranial Disease: A Systematic Review and Meta-analysis

IMPORTANCE

Intracranial metastatic disease (IMD) is a severe complication of cancer with profound prognostic implications. Patients with IMD in the setting of limited or stable extracranial disease (IMD-SE) may represent a unique and understudied subset of patients with IMD with superior prognosis.

OBJECTIVE

To evaluate overall survival (OS), progression-free survival (PFS), and intracranial PFS (iPFS) in patients with IMD-SE secondary to any primary cancer.

DATA SOURCES

Records were identified from MEDLINE, EMBASE, CENTRAL, and gray literature sources from inception to June 21, 2021.

STUDY SELECTION

Studies in English reporting OS, PFS, or iPFS in patients with IMD-SE (defined as IMD and ≤2 extracranial metastatic sites) and no prior second-line chemotherapy or brain-directed therapy were selected.

DATA EXTRACTION AND SYNTHESIS

Author, year of publication, type of study, type of primary cancer, and outcome measures were extracted. Random-effects meta-analyses were performed to estimate effect sizes, and subgroup meta-analysis and metaregression were conducted to measure between-study differences in February 2022.

MAIN OUTCOMES AND MEASURES

The primary end point was OS described as hazard ratios (HRs) and medians for comparative and single-group studies, respectively. Secondary end points were PFS and iPFS.

RESULTS

Overall, 68 studies (5325 patients) were included. IMD-SE was associated with longer OS (HR, 0.52; 95% CI, 0.39-0.70) and iPFS (HR, 0.63; 95% CI, 0.52-0.76) compared with IMD in the setting of progressive extracranial disease. The weighted median OS estimate for patients with IMD-SE was 17.9 months (95% CI, 16.4-22.0 months), and for patients with IMD-PE it was 8.0 months (95% CI, 7.2-12.8 months). Pooled median OS for all patients with IMD-SE was 20.9 months (95% CI, 16.35-25.98 months); for the subgroup with breast cancer it was 20.2 months (95% CI, 10.43-38.20 months), and for non-small cell lung cancer it was 27.5 months (95% CI, 18.27-49.66 months). Between-study heterogeneity for OS and iPFS were moderate (I2 = 56.5%) and low (I2 = 0%), respectively.

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis of patients with IMD-SE, limited systemic disease was associated with improved OS and iPFS. Future prospective trials should aim to collect granular information on the extent of extracranial disease to identify drivers of mortality and optimal treatment strategies in patients with brain metastases.

NRG1/ERBB3/ERBB2 Axis Triggers Anchorage-Independent Growth of Basal-like/Triple-Negative Breast Cancer Cells

ERBB3, also known as HER3, is a tyrosine kinase transmembrane receptor of the ERBB family. Upon binding to neuregulin 1 (NRG1), ERBB3 preferentially dimerizes with HER2 (ERBB2), in turn inducing aggressive features in several cancer types. The analysis of a dataset of breast cancer patients unveiled that higher ERBB3 mRNA expression correlates with shorter relapse-free survival in basal-like breast cancers, despite low ERBB3 expression in this breast cancer subtype. Administration of neuregulin 1 beta (NRG1β) significantly affected neither cellular proliferation nor the basal migratory ability of basal-like/triple-negative quasi-normal MCF10A breast cells, cultured in mono-layer conditions. Furthermore, no significant regulation in cell morphology or in the expression of basal/myoepithelial and luminal markers was observed upon stimulation with NRG1β. In non-adherent conditions, NRG1β administration to MCF10A cells did not significantly influence cell survival; however, it robustly induced cell growth as spheroids (3D growth). Intriguingly, a remarkable upregulation of ERBB3 and ERBB2 protein abundance was observed in 3D compared to 2D cell cultures, and NRG1β-induced 3D cell growth was efficiently prevented by the anti-HER2 monoclonal antibody pertuzumab. Similar results were obtained by the analysis of basal-like/triple-negative breast cancer cellular models, MDA-MB-468 and MDA-MB-231 cells, in which NRG1β induced anchorage-independent cell growth that in turn was prevented or reduced by the simultaneous administration of anti-HER2 neutralizing antibodies. Finally, the ability of pertuzumab in suppressing NRG1β-induced 3D growth was also evaluated and confirmed in MCF10A engineered with HER2-overexpression. We suggest that the NRG1/ERBB3/ERBB2 pathway promotes the anchorage-independent growth of basal-like breast cancer cells. Importantly, we provide evidence that ERBB2 neutralization, in particular by pertuzumab, robustly inhibits this process. Our results pave the way towards the development of novel anticancer strategies for basal-like breast cancer patients based on the interception of the NRG1/ERBB3/ERBB2 signaling axis.