Researchers say they have identified potential prognostic markers and targets for treatment in patients with non–small cell lung cancer (NSCLC) and brain metastases (BM).
There was “substantial” concordance in driver mutations, such as EGFR and KRAS, between BM and primary tumor samples but greater genomic instability in BM samples, reported Hong-Sheng Wang, PhD, of Sun Yat-Sen University in Guangzhou, China, and colleagues.
PI3K signaling was significantly associated with an increased risk of BM, and CDKs and PIK3CA were “potential druggable mutations,” they reported in Cancer.
The researchers conducted a retrospective study of 61 Chinese patients with NSCLC and BM. The patients had adenocarcinoma (n = 50), squamous cell carcinoma (n = 3), and mixed subtypes (n = 8). Less than half of patients (n = 28) had stage IV disease at diagnosis, 36 had metachronous disease, and 25 had synchronous disease. All patients had undergone surgery, 33 had received chemoradiation, 26 had received no systemic treatment, and 5 had been treated with tyrosine kinase inhibitors.
The researchers performed next-generation sequencing on primary tumors and matched BM samples from the 61 patients, targeting 416 cancer-relevant genes.
Results showed high concordance between the primary and BM samples with regard to major driver mutations – 92% for EGFR, 82% for KRAS, and 83% for TP53 mutations.
For nearly half of patients (48%), all mutations found in primary tumor samples were also found in BM samples. In fact, 18% of patients had the same mutational profiles in lung and brain lesions.
Conversely, 30% of patients had more brain-specific mutations, 13% had more lung-specific mutations, 28% had mixed profiles, and 11% had completely unique mutational profiles in lung and brain lesions.
Compared with primary tumor samples, BM samples had a significantly higher frequency of copy number variations (P = .0002); alterations in CDKN2A/2B, CCND1, CDK4, and RB1 (P = .0019); and alterations in PIK3CA, PTEN, STK11, RICTOR, and NF2 (P = .0037).
Patients with activated PI3K signaling in their primary tumors had significantly shorter BM-free survival. The hazard ratio (adjusted for baseline clinicopathologic parameters) was 8.49 (P = .0005).
There was no significant difference in BM-free survival between EGFR-/KRAS-mutated patients and patients with wild-type EGFR/KRAS (P = .29). However, there was a trend toward shorter BM-free survival in patients with TP53 mutations (P = .15).
There was a trend toward shorter BM-free intervals in patients with an activated WNT pathway via CTNNB1 mutations (P = .22) or APC and AXIN2 mutations (P = .015). However, the researchers said these findings should be treated with caution due to a small sample size.
The National Natural Science Foundation of China and the Natural Science Foundation of Guangdong Province supported the research. The researchers disclosed relationships with Geneseeq Technology Inc. in Toronto and Nanjing Geneseeq Technology Inc.
SOURCE: Wang H et al. Cancer. 2019 Jul 9. doi: 10.1002/cncr.32372.
