Non-small cell lung cancer intracranial metastases treatment
Brain metastases are common in patients with non-small cell lung cancer (NSCLC). Because of associated poor prognosis and limited specific treatment options, there is a real need for the development of medical therapies and strategies for affected patients 1).
EGFR and ALK tyrosine kinase inhibitors (TKIs) provide significantly superior systemic response rates and progression free survival compared to standard chemotherapy in the molecularly defined Non-small cell lung cancer (NSCLC) subpopulations. An apparent intracranial activity of new generation TKIs triggered the discussion on their role in brain metastases in lieu of local therapies 2).
The discovery of Epidermal Growth Factor Receptor (EGFR)-activating mutations and Anaplastic Lymphoma Kinase (ALK) rearrangements in patients with non-small cell lung adenocarcinoma has allowed for the introduction of small-molecule tyrosine kinase inhibitors to the treatment of advanced-stage patients. The Epidermal Growth Factor Receptor (EGFR) is a transmembrane protein with tyrosine kinase-dependent activity. EGFR is present in membranes of all epithelial cells. In physiological conditions, it plays an important role in the process of cell growth and proliferation. Binding the ligand to the EGFR causes its dimerization and the activation of the intracellular signaling cascade. Signal transduction involves the activation of MAPK, AKT, and JNK, resulting in DNA synthesis and cell proliferation. In cancer cells, binding the ligand to the EGFR also leads to its dimerization and transduction of the signal to the cell interior. It has been demonstrated that activating mutations in the gene for EGFR-exon19 (deletion), L858R point mutation in exon 21, and mutation in exon 20 results in cancer cell proliferation. Continuous stimulation of the receptor inhibits apoptosis, stimulates invasion, intensifies angiogenesis, and facilitates the formation of distant metastases. As a consequence, cancer progresses. These activating gene mutations for the EGFR are present in 10-20% of lung adenocarcinomas. Approximately 3-7% of patients with lung adenocarcinoma have the echinoderm microtubule-associated protein-like 4 (EML4)/ALK fusion gene. The fusion of the two genes EML4 and ALK results in a fusion gene that activates the intracellular signaling pathway stimulates the proliferation of tumor cells and inhibits apoptosis. A new group of drugs-small-molecule tyrosine kinase inhibitors-has been developed; the first generation includes gefitinib and erlotinib and the ALK inhibitor crizotinib. These drugs reversibly block the EGFR by stopping the signal transmission to the cell. The second-generation tyrosine kinase inhibitor (TKI) afatinib or ALK inhibitor alectinib block the receptor irreversibly. Clinical trials with TKI in patients with non-small cell lung adenocarcinoma with central nervous system (CNS) metastases have shown prolonged, progression-free survival, a high percentage of objective responses, and improved quality of life. Resistance to treatment with this group of drugs emerging during TKI therapy is the basis for the detection of resistance mutations. The T790M mutation, present in exon 20 of the EGFR gene, is detected in patients treated with first- and second-generation TKI and is overcome by Osimertinib, a third-generation TKI. The I117N resistance mutation in patients with the ALK mutation treated with alectinib is overcome by ceritinib. In this way, sequential therapy ensures the continuity of treatment. In patients with CNS metastases, attempts are made to simultaneously administer radiation therapy and tyrosine kinase inhibitors. Patients with lung adenocarcinoma with CNS metastases, without activating EGFR mutation and without ALK rearrangement, benefit from immunotherapy. This therapeutic option blocks the PD-1 receptor on the surface of T or B lymphocytes or PD-L1 located on cancer cells with an applicable antibody. Based on clinical trials, pembrolizumab and all antibodies are included in the treatment of non-small cell lung carcinoma with CNS metastases 3).
A KPS score ≥ 70, RPA class I/II, and postoperative chemotherapy could benefit post-metastasectomy patients with brain metastases (BM) from Non-small cell lung cancer (NSCLC). Conversely, the initial onset of intracranial lesions is an unfavorable factor that increases the risk of death. These findings support the use of personalized therapy for patients with BM from NSCLC 4).
A article of Preusser et al., is the result of a round table discussion held at the European Lung Cancer Conference (ELCC) in Geneva in May 2017. Its purpose was to explore and discuss the advances in the knowledge about the biology and treatment of brain metastases originating from non-small cell lung cancer. The authors propose a series of recommendations for research and treatment within the discussed context 5).
PUBMED, EMBASE, the Cochrane Library, Web of Knowledge, Current Controlled Trials, Clinical Trials, and 2 conference websites were searched to select NSCLC patients with only single brain metastasis (SBM) who received brain surgery or SRS. SPSS 18.0 software was used to analyze the mean median survival time (MST) and Stata 11.0 software was used to calculate the overall survival (OS).
A total of 18 trials including 713 patients were systematically reviewed. The MST of the patients was 12.7 months in surgery group and 14.85 months in SRS group, respectively. The 1, 2, and 5 years OS of the patients were 59%, 33%, and 19% in surgery group, and 62%, 33%, and 14% in SRS group, respectively. Furthermore, in the surgery group, the 1 and 3 years OS were 68% and 15% in patients with controlled primary tumors, and 50% and 13% in the other patients with uncontrolled primary tumors, respectively. Interestingly, the 5-year OS was up to 21% in patients with controlled primary tumors.
There was no significant difference in MST or OS between patients treated with neurosurgery and SRS. Patients with resectable lung tumors and SBM may benefit from the resection of both primary lesions and metastasis 6).
Patients with NSCLC and synchronous brain metastases, presenting neurological symptoms showed no survival benefit from neurosurgical resection, although quality of life was improved due to early control of neurological symptoms 7).
Response rates after platinum based antineoplastics, range from 23% to 45%. Development of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs): gefitinib or erlotinib, was an improvement in treatment of advanced NSCLC patients. EGFR mutations are present in 10-25% of NSCLC (mostly adenocarcinoma), and up to 55% in never-smoking women of East Asian descent. In the non-selected group of patients with BMF-NSCLC, the overall response rates after gefitinib or erlotinib treatment range from 10% to 38%, and the duration of response ranges from 9 to 13.5 months. In the case of present activating EGFR mutation, the response rate after EGRF-TKIs is greater than 50%, and in selected groups (adenocarcinoma, patients of Asian descent, never-smokers, asymptomatic BMF-NSCLC) even 70%. Gefitinib or erlotinib treatment improves survival of BMF-NSCLC patients with EGFR mutation in comparison to cases without the presence of this mutation. There is no data on the activity of the anti-EML4-ALK agent crizotinib. Bevacizumab, recombinant humanised monoclonal antibody anti-VEGF, in the treatment of advanced non-squamous NSCLC patients is a subject of intense research. Data from a clinical trial enrolling patients with pretreated or occult BMF-NSCLC proved that the addition of bevacizumab to various chemotherapy agents or erlotinib is a safe and efficient treatment, associated with a low incidence of CSN haemorrhages. However, the efficacy and safety of bevacizumab used for therapeutic intent, regarding active brain metastases is unknown 8).