Immunotherapy in NSCLC patients with brain metastases. Understanding brain tumor microenvironment and dissecting outcomes from immune checkpoint blockade in the clinic

BACKGROUND

Brain metastases are frequent complications in patients with non-small-cell lung cancer (NSCLC) associated with significant morbidity and poor prognosis. Our goal is to give a global overlook on clinical efficacy from immune checkpoint inhibitors in this setting and to review the role of biomarkers and molecular interactions in brain metastases from patients with NSCLC.

METHODS

We reviewed clinical trials reporting clinical outcomes of patients with NSCLC with brain metastases as well as publications assessing the tumor microenvironment and the complex molecular interactions of tumor cells with immune and resident cells in brain metastases from NSCLC biopsies or preclinical models.

RESULTS

Although limited data are available on immunotherapy in patients with brain metastases, immune checkpoint inhibitors alone or in combination with chemotherapy have shown promising intracranial efficacy and safety results. The underlying mechanism of action of immune checkpoint inhibitors in the brain niche and their influence on tumor microenvironment are still not known. Lower PD-L1 expression and less T CD8⁺ infiltration were found in brain metastases compared with matched NSCLC primary tumors, suggesting an immunosuppressive microenvironment in the brain. Reactive astrocytes and tumor associated macrophages are paramount in NSCLC brain metastases and play a role in promoting tumor progression and immune evasion.

CONCLUSIONS

Discordances in the immune profile between primary tumours and brain metastases underscore differences in the tumour microenvironment and immune system interactions within the lung and brain niche. The characterization of immune phenotype of brain metastases and dissecting the interplay among immune cells and resident stromal cells along with cancer cells is crucial to unravel effective immunotherapeutic approaches in patients with NSCLC and brain metastases.

Response of Leptomeningeal Metastases in EGFR-Mutated Non-Small-Cell Lung Cancer to Afatinib in the Absence of Radiotherapy

Palliative radiotherapy is currently the medical standard of care for non-small-cell lung cancer (NSCLC) patients with symptomatic CNS and leptomeningeal disease. We report the case of a 62-year-old male patient with EGFR mutation (del19+) NSLC with symptomatic lymph node, bone, CNS, and leptomeningeal metastases. Taking into account on one hand the response to tyrosine kinase inhibitors (TKIs) and on the other hand the short- to medium-term side effects of radiotherapy and the lack of timely availability in our healthcare system, the patient was treated with afatinib (40 mg daily) and exhibited a rapid response with improvement of neurological symptoms. The patient presented partial response of extracranial, CNS, and leptomeningeal lesions at 3, 6, and 12 months of treatment, currently completing 16 months of progression-free survival despite presenting mild dermatological and gastrointestinal toxicities. Afatinib is an effective and safe option in patients with NSLC EGFR mutation del19+ with CNS and leptomeningeal compromise avoiding or delaying radiotherapy and its side effects, especially in countries where there is a lack of access to this kind of therapy.

EGFR-TKIs plus bevacizumab demonstrated survival benefit than EGFR-TKIs alone in patients with EGFR-mutant NSCLC and multiple brain metastases

INTRODUCTION

Previous studies suggested that epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKIs) plus bevacizumab could significantly prolong progression-free survival (PFS) than EGFR-TKI alone as first-line setting for patients with EGFR-mutant non-small-cell lung cancer (NSCLC). However, whether this combination could benefit patients with multiple brain metastases (BrMs) remains undetermined.

METHODS

A total of 208 patients with EGFR-mutant NSCLC and multiple BrM (number >3, at least one of lesions was measurable) were retrospectively identified. Kaplan-Meier curves with two-sided log-rank tests and Cox proportional hazards model with calculated hazard ratios and 95% confidence intervals were used to determine the survival difference.

RESULTS

Of all patients, 149 patients received EGFR-TKIs monotherapy and 59 received EGFR-TKIs plus bevacizumab as first-line setting. EGFR-TKIs plus bevacizumab was associated with a significantly higher intracranial objective response rate (ORR, 66.1% vs. 41.6%, P = 0.001), systemic ORR (74.6% vs. 57.1%, P = 0.019), longer intracranial PFS (14.0 vs. 8.2 months; P < 0.001) and systemic PFS (14.4 vs. 9.0 months; P < 0.001). Importantly, addition of bevacizumab also had a significantly longer overall survival (OS, 29.6 vs. 21.7 months; P < 0.001). Multivariate analysis consistently revealed that addition of bevacizumab was independently associated with prolonged intracranial and systemic PFS, and OS. No unexpected serious adverse effects were observed.

CONCLUSIONS

EGFR-TKIs plus bevacizumab prolonged not only PFS but also OS in patients with EGFR-mutant NSCLC and multiple BrMs when compared with EGFR-TKIs alone, indicating that this combination could be an alternative therapeutic option for those patients.

Systemic therapy for brain metastases

Metastases from cells outside of the central nervous system are the most common cancer found in the brain and are commonly associated with poor prognosis. Although cancer treatment is improving overall, central nervous system metastases are becoming more prevalent and require finesse to properly treat. Physicians must consider the biology of the primary tumor and the complex neurological environment that the metastasis resides in. This can be further complicated by the fact that the practice of cancer management is constantly evolving and therapy that works outside of the blood-brain barrier may not be effective inside of it. Therefore, this review seeks to update the reader on recent advancements made on the three most common sources of brain metastases: lung cancer, breast cancer, and melanoma. Each of these malignancies has been the subject of intriguing and novel avenues of therapy which are reviewed here.

The Future Is Now-Prospective Study of Radiosurgery for More Than 4 Brain Metastases to Start in 2018!

Stereotactic radiosurgery (SRS) has replaced whole brain radiotherapy (WBRT) as standard therapy for most patients with four or fewer brain metastases due to improved cognitive outcomes and more favorable health related quality of life (QoL). Whether SRS or WBRT is the optimal radiation modality for patients with five to fifteen brain metastases remains an open question. Efforts are underway to develop prospective evidence to answer this question. One of the planned trials is a Canadian Cancer Trials Group (CCTG)-lead North American intergroup trial. In general cancer treatments must have two basic aims: prolonging and improving QoL. In this vein, the selection of overall survival and QoL metrics as outcomes appear obvious. Potential secondary outcomes are numerous: patient/disease related, treatment related, economic, translational, imaging, and dosimetric. In designing a trial, one must also ponder what is standard WBRT—specifically, whether it should be associated with memantine. With the rapid accrual of an intergroup trial of hippocampal-sparing WBRT, we may find that the standard WBRT regimen changes in the course of planned trials. As up-front radiosurgery is increasingly used for more than 4 brain metastases without high level evidence, we have a window of opportunity to develop high quality evidence which will help guide our future clinical and policy decisions.

Osimertinib as first-line therapy in advanced NSCLC: a profile of its use

Osimertinib (Tagrisso^®) is an oral, CNS-active, third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that selectively inhibits EGFR TKI-activating mutations over wild-type EGFR in patients with advanced non-small cell lung cancer (NSCLC), including the T790M mutation that often underlies acquired resistance to earlier generation EGFR TKIs. Relative to standard of care first-generation EGFR TKIs (erlotinib or gefitinib) as first-line treatment of EGFR activating mutation-positive advanced NSCLC, osimertinib significantly prolongs median progression-free survival (PFS), with separation of the Kaplan-Meier PFS survival curves evident by the first assessment timepoint of 6 weeks. Osimertinib prolongs PFS relative to standard EGFR TKI therapy in all prespecified groups, irrespective of the EGFR mutation present at study entry and presence of CNS metastases at study entry. Overall survival data are not yet mature. Osimertinib has a generally manageable tolerability profile.