RESEARCH ARTICLE

EGFR mutation status and its impact on survival of Chinesenon-small cell lung cancer patients with brain metastases

Dongdong Luo & Xin Ye & Zheng Hu & Kaiwen Peng &

Ye Song & Xiaolu Yin & Guanshan Zhu & Qunsheng Ji &Yuping Peng

Received: 11 September 2013 /Accepted: 14 October 2013# International Society of Oncology and BioMarkers (ISOBM) 2013

Abstract Brain metastasis (BM) is a leading cause of death inpatients with non-small cell lung cancer (NSCLC). EGFRmutations in primary NSCLC lesions have been associatedwith sensitivity to EGFR tyrosine kinase inhibitor (TKI).Therefore, it has become important to understand EGFRmutation status in BM lesions of NSCLC, and its clinicalimplications. BM samples of 136 NSCLC patients from SouthChina, in which 15 had paired primary lung tumors, wereretrospectively analyzed for EGFR mutation by amplificationmutation refractory system (ARMS). Effect of BM EGFRmutations on progression-free survival (PFS) and overallsurvival (OS) was evaluated by Kaplan–Meier curves andlog-rank test. EGFR mutations were detected in 52.9 % (72of 136) of the BM lesions, with preference in female andnever-smokers. A concordance rate of 93.3 % (14 of 15)was found between the primary NSCLC and correspondingBM. Positive prediction value of testing primary NSCLCs forBM EGFR mutation is 100.0 %, and negative predictionvalue is 87.5 %. Median PFS of BM surgery was 12 and10 months (P=0.594) in the wild-type and mutant group,respectively. Median OS of BM surgery was 24.5 and15 months (P=0.248) in the wild-type and mutant group,respectively. In conclusion, EGFR mutation status is highlyconcordant between the primary NSCLC and corresponding

BM. The primary NSCLC could be used as surrogate samplesto predict EGFR mutation status in BM lesions or vice versa.Moreover, EGFR mutations showed no significant effect onPFS or OS of NSCLCs with BM.

Key words Brain metastasis .EGFR mutations . Non-smallcell lung cancer

Introduction

Lung cancer is the leading cause of cancer-related mortalityworldwide [1]. Non-small cell lung cancer (NSCLC) accountsfor approximately 85 % of all lung cancers, with the mostprevalent subtype, adenocarcinoma, markedly increasing inincidence over recent years [2]. Brain is one of the mainmetastatic sites in patients with lung cancer, and brainmetastases (BMs) remain a major cause of morbidity andmortality. Nearly 50 % of NSCLC patients with distalmetastasis will be affected by BM during the course of disease[3, 4].

EGFR mutation has been demonstrated to be an importantcontributor to the development of NSCLC in Asia population[5, 6]. The small molecular EGFR tyrosine kinase inhibitors(EGFR-TKIs), gefinitib and erlotinib, are currently used forthe treatment of patients with advanced NSCLC harboringsomatic EGFR mutations with 60–80 % response rate [7, 8].Recently, clinical activity of gefitinib in BMs was alsoobserved in some NSCLC patients, indicating the existenceof activating EGFR mutations in the brain metastatic lesions[9, 10]. Therefore, it becomes clinically important tounderstand EGFR mutation status in the BMs of NSCLC.

In patients with advanced NSCLC, it might not be practicalto retrieve the BM lesions in most cases. The primary lungtumor could be the only tissue sample available for EGFRmutation detection. In some other cases, biopsy or resection of

D. Luo and X. Ye contributed equally to this work.

D. Luo : Z. Hu :K. Peng :Y. Song :Y. Peng (*)Department of Neurosurgery, Nanfang Hospital,Southern Medical University, Guangzhou 510515, Chinae-mail: pengyupingch@yeah.net

D. LuoDepartment of Neurosurgery, Cancer Center of Guangzhou MedicalUniversity, Guangzhou 510095, China

X. Ye :X. Yin :G. Zhu :Q. JiInnovation Center China of AstraZeneca R&D, Shanghai, China

Tumor Biol.DOI 10.1007/s13277-013-1323-9

BMs may be the first step to enable histological diagnosis,while neither biopsy nor resection of primary tumor could takeplace. In either scenario, it would be important to understandwhether the EGFR mutation status is consistent betweenprimary lung tumor and BM lesions for a better predictionof TKI therapy. In this study, 136 BM samples from ChineseNSCLC patients, including 15 corresponding primary lungtumors, were evaluated for the EGFR mutation frequency andconcordance. In addition, progression-free survival (PFS) andoverall survival (OS) of these patients following surgicalresection of BM lesions were also studied retrospectively.

Material and methods

Patients and tumor samples

We retrospectively evaluated NSCLC patients with metastaticdissemination to the brain, who had been enrolled in eightcenters in south China from November 2007 to November2012. Formalin-fixed, paraffin-embedded tissues of primarytumors and corresponding BMs obtained from histologicallyconfirmed NSCLC patients were included. A total of 136patients were included, whose BM samples of resection orbiopsy were obtained. Among these patients, 15 had matchedprimary lung tumor samples obtained by resection or biopsy.All tissue samples went through pathological evaluation onceagain in the center of Southern Medical University AffiliatedNanfang Hospital to confirm the diagnosis of NSCLC and thepercentage of tumor cells. As the analytical sensitivity ofamplification mutation refractory system (ARMS) assay isaround 1 %, only the tumor specimens with more than 1 %of tumor contents were qualified for the following EGFRmutation evaluation in primary tumors and matchedmetastases.

Clinical characteristics, including age, sex, smokinghistory, treatment, time to progression and survival time, wereobtained frommedical records from the eight centers. Clinicalstaging was performed according to the 7th AJCC CancerStaging System [11].

The study was reviewed and approved by the InstitutionalReview Board of Southern Medical University AffiliatedNanfang Hospital. All patients gave their informed consentto participate in this study.

DNA extraction and quality check

QIAamp DNA formalin-fixed paraffin-embedded Tissue Kit(Qiagen, Hilden, Germany) was used for DNA extractionfrom tumor tissue samples following the instruction of themanufacturer. Extracted DNA samples were quantified withthe real-time quantitative PCR method using commercialTaqman assay for RNase P gene (Life Technologies, USA).

The concentration of each DNA sample was normalized to0.4 ng/μl whenever possible. The concentration of 29 DNAsamples was lower than 0.4 ng/μl, for which the originalconcentration was applied.

EGFR mutation analysis

The EGFR Mutation Detection Kit (Amoy Diagnostics,Xiamen, China), which is based on the ARMS technology,was used to detect the 29 most common types of EGFRmutations in lung cancer. All experiments were performedfollowing the user manual. Briefly, 4.7 μl DNA was addedto 35.3 μl PCR master mix of each assay which contains PCRprimers, fluorescent probes, PCR buffer, and Taq DNApolymerase. PCR thermal cycling was as follows: 5 minincubation at 95 °C, followed by 15 cycles of 95 °C for25 s, 64 °C for 20 s, 72 °C for 20 s, and then 31 cycles of93 °C for 25 s, 60 °C for 35 s, 72 °C for 20 s. The primersequences for EGFR gene were as follows: forward primer5′- CTCTTACACCCAGTGGAGAA-3′, reverse primer 5′-CATCCACTTGATAGGCA CTT-3′, the length is 572 bp.Fluorescent signal was collected from FAM and HEXchannels. The results were analyzed according to theinstructions in the user manual.

Statistic analysis

The McNemar's test and Pearson Chi-square test were used todetermine whether EGFR mutation differed significantlybetween primary tumors and corresponding BMs. PearsonChi-square test was used to determine whether EGFRmutation was significantly relevant to the correspondingclinical characteristics. P values less than 0.05 wereconsidered statistically significant (difference). An associationbetween mutation status of EGFR and survival outcomes wasanalyzed. PFS was assessed from the date of BM surgery tothe date of the first recurrence, second primary lungmalignancy, any other metastases, or death from any cause.OS was calculated from the date of BM surgery to the date ofthe last follow-up or death from any cause. Kaplan–Meiercurves were generated for PFS and OS. The survivaldifference between groups was assessed by the log-rank test.A P value less than 0.05 was considered statisticallysignificantly different. SPSS 13.0 (SPSS, Chicago, IL) forWindows was used for the statistical analyses.

Results

Clinical characteristics of the patients

Clinical characteristics of the 136 patients are shown inTable 1. Median age of the patients at initial diagnosis was

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Table 1 Correlation of clinical characteristics with EGFR mutation in NSCLC patients with BM

No. of Patients EGFRvalue (%) (n=136) WT (n =64) MT (n =72) P value

Age at Diagnosis 0.293

Median 55 (range, 26–79)

≥55 years 70 (51.5 %) 36 (51.4 %) 34 (48.6 %)

<55 years 66 (48.5 %) 28 (42.4 %) 38 (57.6 %)

Sex 0.000

Male 83 (61.0 %) 53 (63.9 %) 30 (36.1 %)

Female 53 (39.0 %) 11 (20.8 %) 42 (79.2 %)

Smoking history 0.000

Never-smoker 73 (53.7 %) 27 (37.0 %) 46 (63.0 %)

Former and current smoker 51 (37.5 %) 35 (68.6 %) 16 (31.4 %)

Unknown 12 (8.8 %) 2 (16.7 %) 10 (83.3 %)

KPS 0.189

50 5 (3.7 %) 5 (100.0 %) 0 (.0 %)

60 20 (14.7 %) 8 (40.0 %) 12 (60.0 %)

70 24 (17.6 %) 11 (45.8 %) 13 (54.2 %)

80 62 (45.6 %) 28 (45.2 %) 34 (54.8 %)

90 25 (18.4 %) 12 (48.0 %) 13 (52.0 %)

Stage at diagnosis (Stage T) 0.828

T1 75 (55.1 %) 33 (44.0 %) 42 (56.0 %)

T2 52 (38.2 %) 27 (51.9 %) 25 (48.1 %)

T3 5 (3.7 %) 2 (40.0 %) 3 (60.0 %)

T4 4 (2.9 %) 2 (50.0 % 2 (50.0 %)

Stage at diagnosis (Stage N) 0.198

N0 51 (37.5 %) 30 (58.8 %) 21 (41.2 %)

N1 33 (24.3 %) 14 (42.4 %) 19 (57.6 %)

N2 39 (28.7 %) 15 (38.5 %) 24 (61.5 %)

N3 13 (9.6 %) 5 (38.5 %) 8 (61.5 %)

Primary sites in lung 0.902

Right Lung 80 (58.8 %) 38 (47.5 %) 42 (52.5 %)

Left Lung 56 (41.2 %) 26 (46.4 %) 30 (53.6 %)

Metastatic sites in brain 0.141

Right cerebral hemisphere 62 (45.6 %) 24 (38.7 %) 38 (61.3 %)

Left cerebral hemisphere 41 (30.1 %) 19 (46.3 %) 22 (53.7 %)

Right cerebellar hemisphere 21 (15.4 %) 13 (61.9 %) 8 (38.1 %)

Left cerebellar hemisphere 12 (8.8 %) 8 (66.7 %) 4 (33.3 %)

Brain metastases number of lesions 0.898

Single 90 (66.2 %) 42 (46.7 %) 48 (53.3 %)

Multiple 46 (33.8 %) 22 (47.8 %) 24 (52.2 %)

Brain metastases size of largest lesions 0.490

<2 cm 9 (6.6 %) 3 (33.3 %) 6 (66.7 %)

≥2 cm, ≤3c m 38 (27.9 %) 15 (39.5 %) 23 (60.5 %)

≥3 cm, ≤4 cm 45 (33.1 %) 24 (53.3 %) 21 (46.7 %)

>4 cm 44 (32.4 %) 22 (50.0 %) 22 (50.0 %)

Pathological grading

Undifferentiation 2 (1.5 %) 2 (100.0 %) 0 (.0 %)

Poorly differentiated 69 (50.7 %) 32 (46.4 %) 37 (53.6 %)

Moderately differentiated 60 (44.1 %) 30 (50.0 %) 30 (50.0 %)

Highly differentiated 5 (3.7 %) 0 (.0 %) 5 (100.0 %)

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55 years (range, 26–79 years). No statistical significance (P=0.293) was shown for EGFR mutation status in different agegroups (cut point at 55 years). Overall, 86 (61.0 %) patientswere men and 53 (39.0 %) were women. Women had a higherrisk for EGFR mutations (P=0.000). Fifty-one (37.5 %)patients had a history of smoking, and EGFR mutation ratewas higher in non-smokers (P =0.000). The KarnofskyPerformance Status (KPS) Score of the patients was 50–90 at presentation. All the patients had stage IV disease whenBMs were diagnosed. In this cohort, 58.8 % of the primarytumors occurred in the right lung, and 75.7% of the BMswerelocated in cerebral hemisphere, while 24.3 % were incerebellar hemisphere. Overall, 66.2 % of BM lesions weresingle and 65.5 % had the largest lesion (i.e., >3 cm in size).And 112 (82 .4 %) samples were d iagnosed as

adenocarcinoma; no significant difference in EGFR mutationstatus was observed among the different pathological types ofNSCLC (P=0.183). A total of 129 (94.8 %) samples werepathologically staged as being poorly or moderatelydifferentiated. The clinical symptoms in the patients withBM included intracranial hypertension (75.7 %), paraesthesia(9.6 %), paralysis (22.8 %), ataxia (21.3 %), seizure (11.8 %),aphasia (5.9 %) and loss of attention (36.8 %). It is worthnoting that 108 (79.4 %) patients were initially admittedwithout any pulmonary symptoms at presentation. The brainmetastatic lesions in all patients were surgically removed, and42 (30.9 %) patients had undergone whole brain radiationtherapy (WBRT) after the operation, and 13 (9.6 %) hadundergone stereotactic radiotherapy (SRT). Moreover, 57(41.9 %) patients received postoperative adjuvant therapy

Table 1 (continued)

No. of Patients EGFRvalue (%) (n=136) WT (n =64) MT (n =72) P value

Pathological classification 0.183

Adenocarcinoma 112 (82.4 %) 48 (42.9 %) 64 (57.1 %)

Squamous cell carcinoma 5 (3.7 %) 3 (60.0 %) 2 (40.0 %)

Adenosquamous carcinoma 8 (5.9 %) 6 (75.0 %) 2 (25.0 %)

Others (large cell carcinoma) 11 (8.1 %) 7 (63.6 %) 4 (36.4 %)

Pulmonary symptoms at diagnosis 0.768

Cough 22 (16.2 %) 10 (45.5 %) 12 (54.5 %)

Blood sputum 6 (4.4 %) 2 (33.3 %) 4 (66.7 %)

No specific symptoms 108 (79.4 %) 52 (48.1 %) 56 (51.9 %)

Brain symptoms at diagnosis

Intracranial hypertension 103 (75.7 %) 47 (45.6 %) 56 (54.4 %)

Paraesthesia 13 (9.6 %) 3 (23.1 %) 10 (76.9 %)

Palalysis 31 (22.8 %) 16 (51.6 %) 15 (48.4 %)

Ataxia 29 (21.3 %) 16 (55.2 %) 13 (44.8 %)

Seizure 16 (11.8 %) 7 (43.8 %) 9 (56.2 %)

Aphasia 8 (5.9 %) 2 (25.0 %) 6 (75.0 %)

Loss of attention 50 (36.8 %) 23 (46.0 %) 27 (54.0 %)

Treatment

WBRT 42 (30.9 %) 25 (59.5 %) 17 (40.5 %)

SRT 13 (9.6 %) 8 (61.5 %) 5 (38.5 %)

Adjuvant chemotherapy 57 (41.9 %) 30 (52.6 %) 27 (47.4 %)

EGFR TK inhibitors 7 (5.1 %) 0 (.0 %) 7 (100.0 %)

Progression-free survivor

Mean ± SD 13.763±11.0014

Survival

Death 83 (61.0 %) 38 (45.8 %) 45 (54.2 %)

Live 24 (17.6 %) 12 (50.0 %) 12 (50.0 %)

Censoring 29 (21.3 %) 14 (48.3 %) 15 (51.7 %)

Mean ± SD 19.572±14.7856

EGFR epidermal growth factor receptor, MT mutant, WT wild-type, KPS Karnofsky Performance Status, WBRT whole brain radiation therapy, SRTstereotactic radiotherapy, TK inhibitors tyrosine kinase inhibitors

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with Platinum, Taxanes or/and Pemetrexed. Seven (5.1 %)patients were administered with EGFR TKI during the courseof the disease.

EGFR mutation status in BM and primary lung lesionsof the NSCLC patients

EGFR mutation status of 136 brain metastatic samples inNSCLC patients is presented in Table 2. EGFR mutationwas detected in 72 (52.9 %) patients. Sixty-two (86.1 %)patients carried either leucine-to-arginine mutation in exon21 (L858R, 26/72, 36.1 %) or deletion in exon 19 (19-Del,36/72, 50.0 %). Six (8.3 %) patients had 19-Del&L858R

double mutations. The remaining four patients hadG719X&L861Q, 19-Del&G719X, 19-Del&Ins-20, andL861Q, respectively. The statistical analysis among thedifferent EGFR mutations are also listed in Table 2.

EGFR mutation status comparison between primaryNSCLC and the corresponding BM was also analyzed, andis shown in Table 3. EGFR mutation status was classified as:(1) EGFR wild-type in both primary tumor and BM (n =7,46.7 %), (2) EGFR mutation in primary tumor (n =0, 0.0 %)or in BM (n =1, 6.7 %), and (3) EGFR mutation in bothprimary tumor and metastasis (n =7, 46.7 %). Overall, EGFRmutation status showed a concordance rate of 93.3 % (14 of15 patients) between the primary lung lesions andcorresponding BMs. No statistically significant difference(McNemar's test, P=1.000; Kappa test, κ=0.867, P=0.000)was observed between these two groups. The positiveprediction value (PPV) of testing primary lung lesions forBM EGFR mutation status is 100.0 % (7/7), and the negativeprediction value (NPV) is 87.5 % (7/8). On the other hand, thePPV of testing BM lesions for primary lung lesion EGFRmutation is 87.5 % (7 out of 8) and the NPV is 100.0 % (7/7)(see Table 4).

The EGFR mutation status of 136 BMs with 15 primarylung lesions is presented in Table 5. The EGFR mutation ratein primary NSCLC lesions was 46.7 % (7/15 patients). Nostatistical significance of EGFR mutation rate (Pearson Chi-square test, χ 2=0.213, P =0.644) was seen between theprimary lung lesions and BMs in those NSCLC patients.

Table 2 EGFR mutation type and frequency in 136 NSCLC brainmetastases

EGFR mutation Frequency (%) P1 P2 P3

L858R 26 (36.1 %) – 0.032 0.013

19-Del 36 (50.0 %) 0.032 – 0.011

19-Del/L858R 6 (8.3 %) 0.013 0.011 –

G719X/L861Q 1 (1.4 %) 0.004 0.002 0.421

19-Del/G719X 1 (1.4 %) 0.003 0.001 0.381

19-DeL/20-Ins 1 (1.4 %) 0.002 0.001 0.293

L861Q 1 (1.4 %) 0.004 0.002 0.492

P1 EGFRmutations vs. L858R EGFRmutation, P2 EGFRmutations vs.19-Del EGFR mutation, P3 EGFR mutations vs. 19-Del/L858R EGFRmutation

Table 3 Comparison of EGFR mutation between the primary lung lesions and paired brain metastases in 15 NSCLC patients

Case Sex Age Smoking history Pathology diagnosis EGFR mutation

Primary BM Primary BM

1 F 38 Never SCC SCC WT WT

2 M 47 Active AC AC WT WT

3 M 43 Active Mixed SCC-AC Mixed SCC-AC WT WT

4 M 55 Active AC AC L858R L858R

5 M 74 Active Mixed SCC-AC Mixed SCC-AC 19-del 19-del

6 M 68 Never AC AC WT WT

7 M 63 Active AC Poorly differentiated NSCLC WT 19-del

8 M 44 Active Mixed SCC-AC AC 19-del 19-del

9 F 45 Never AC AC L858R L858R

10 F 59 Never AC AC WT WT

11 M 67 Active AC AC L858R L858R

12 F 59 Never Mixed SCC-AC AC 19-del 19-del

13 M 50 Never SCC Mixed SCC-AC WT WT

14 M 48 Active AC AC 19-del 19-del

15 M 55 Active AC AC WT WT

EGFR epidermal growth factor receptor,WT wild-type, SCC squamous cell carcinoma, AC adenocarcinoma, NSCLC non-small-cell lung cancer, BMbrain metastases

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Correlation of EGFR mutation with survival outcomesof the patients

PFS was not significantly different between the wild-typegroup versus the mutant group (P=0.594) with median PFSof 12 months (95 % confidence interval, 6.362–17.638) and10 months (95 % confidence interval, 7.428–12.572) (Fig. 1),respectively.

OS was not significantly different between the mutantgroup and the wild-type group (P=0.248). Median OS was24.5 months in the wild-type group (95 % confidence interval,17.007–31.993) and 15 months in the mutant group (95 %confidence interval, 9.667–20.333) (Fig. 2).

Discussion

To our best knowledge, this is the largest cohort of BM lesionsanalyzed for EGFR mutation and its clinical implications inChinese NSCLC patients. Our results showed a similar levelof EGFR mutation frequency in BMs (52.9 %, 72/136) as inthe primary NSCLC tumors (46.7 %, 7/15) (P=0.644). Inaddition, a high concordance rate (93.3 %) of EGFR mutationstatus was shown between the primary lung andcorresponding brain lesions. Recently, two other studies inEast Asian NSCLC patients were reported with similarfindings although the sample sizes were smaller. Matsumotoet al. [12] found EGFR mutations in 63 % (12/19) of BMs

from Japanese NSCLC patients. Moreover, six of eight pairsof cases were positive for EGFR mutation and theconcordance rate was 100 %. Gow et al. [13] identified44 % (11/25) of EGFR mutation rate in BMs of NSCLCpatients from Taiwan [13]. The concordance rate betweenthe primary lung tumor and BMs was increased from 68 %to 84 % when a more sensitive method (SARMS) was used ascompared to direct DNA sequencing. In Caucasianpopulation, three studies evaluated the EGFR mutation inBM of NSCLCs and identified only 0–2% of EGFR mutationrate in both the primary lung tumors and the BMs [14–16].

Table 4 Combined analysis of EGFR mutation in the primary NSCLCand paired brain metastases

EGFR mutation, no. (%)

Primary BM Total

EGFRWT EGFR MT

EGFR wt 7 (87.5 %) 1 (12.5 %) 8

EGFR mt 0 (.0 %) 7 (100.0 %) 7

Total 7 (46.7 %) 8 (53.3 %) 15

EGFR epidermal growth factor receptor, WT wild type, MT mutant,NSCLC non-small-cell lung cancer, BM brain metastases

Table 5 EGFR mutation frequency in primary lung lesions and brainmetastasis

EGFR mutation, no. (%)

EGFRWT EGFR MT Total

Primary 8 (53.3 %) 7 (46.7 %) 15

Metastasis 64 (47.1 %) 72 (52.9 %) 136

EGFR epidermal growth factor receptor,WT wild-type,MT mutant type,NSCLC non-small-cell lung cancer

Fig. 1 Kaplan–Meier survival curves for progression free survivalbetween mutation group and wild-type group. EGFR epidermal growthfactor receptor, WT wild-type, MT mutation

Fig. 2 Kaplan–Meier survival curves for overall survival betweenmutant group and wild-type group. EGFR epidermal growth factorreceptor, WT wild-type, MT mutation

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The biased population with predominant smokers and malesmight explain the far lower EGFR mutation rate than thepreviously reported 10 % in Caucasian patients [8].

In our study, one out of the 15 patients with paired sampleswas detected to be wild-type EGFR in the primary lung lesionand 19-Del in the corresponding BMs. This might beattributed to the potential heterogeneity of primary lung tumortissue [17]. Considering the high concordance of EGFRmutation status between primary lung tumor and BMs, EGFRmutation detected at one site (lung or brain) could be used as apredictor for the status of another site (brain or lung). The PPVof testing primary lung lesions for BM EGFR mutation statusis 100.0 %, and the negative prediction value is 87.5 %.Similar prediction value is to be obtained by testing BMsamples for primary lung EGFR mutation status. For theadvanced NSCLC patients, whose BMs were not clinicallyeligible for surgery or biopsy due to the health condition ofpatients or the characters of BM lesions, such as miliarymetastases, the primary lung lesion could be used as surrogatesamples to predict the EGFR mutation status in the BMlesions. Under some other circumstances, brain lesions werefound at presentation before primary lung cancer is detectable.In our study, 108/136 (79.4 %) patients were initially admittedwith a variety of craniocerebral disorders without anypulmonary symptoms at presentation. Resection of BMsmay become the first step in treatment for symptomaticreasons and/or to prolong survival. Therefore, for thesepatients, brain lesions might be the only available tissue fordetermination of EGFR status, and the status might help topredict the patients' response to EGFR-TKI therapy.

Heimberger et al. reported that TKIs did not readily crossthe blood–brain barrier (BBB) [18]. The study by Zhang et al.[19] had found that the concentration of gefitinib in the CSFwas low, and increase in the doses of gefitinib was effectivefor the new intracranial lesions. It was also shown thatcontinuous administration of EGFR-TKI followingradiotherapy after progressive disease in isolated metastasisappeared to be a valid treatment option [20]. Therefore, whenusing EGFR-TKI to control the BMs, the high dose mighthave helped to increase the TKI concentration in CSF andimprove curative effect. Hence, a new generation of EGFR-TKI with better BBB penetration property would be attractivefor treatment of NSCLC patients with BMwith the foundationthat the EGFR mutation status of the BM is mostly the sameas primary lung lesion in NSCLC patients.

We also conducted a comprehensive analysis of thecharacteristics of the NSCLC patients as well as theirBM lesions stratified by the EGFR mutation status.Similar to the reports on primary tumors, EGFR mutationsin the BM occur more frequently in females and never-smokers. No significant difference was found in terms of thenumber or the size of the BM in the patients with or withoutEGFR mutations.

The reports about the relationship between the EGFRmutation status and patients' survival have been controversial.It was reported that the presence of EGFR mutations was anindependent prognostic factor in patients with BMs and wasassociated with longer survival [21]. In our study, however,EGFR mutations showed no significant effect on PFS or OS.The study by Nose et al. [22] showed similar findings to ours.They found that mutant or wild-type EGFR had no influenceon the PFS of 393 Japanese patients with stage I–IV lungadenocarcinoma that underwent complete resection. On theother hand, Lee et al. [23] have reported that tumors harboringEGFR mutations had lower risk of recurrence than thoseharboring the wild-type EGFR in curatively resected lungadenocarcinoma. There might be several factors that led tothe inconsistent findings. The major one could be the use ofEGFR-TKI therapy in different cohorts. It is reported thatpatients who received EGFR-TKI at any time after diagnosisof BMs survived longer than those who did not [21, 24]. Thirty-two out of 73 recurred patients in the report by Lee et al. hadbeen receiving salvage therapy with EGFR-TKIs. However,only seven of 136 patients had TKI therapy in our study.

In conclusion, EGFR mutations occur in more than half ofthe NSCLC BM lesions with preference for females andnever-smokers. More than 90 % of the NSCLC patients havethe same EGFR mutations between the primary lung tumorsand the corresponding BM lesions. The EGFR mutationfrequency of BM is largely consistent with that of primarylesion in these NSCLC patients. Therefore, the primary lungtumor samples could be used as surrogate tissues to assess theEGFR mutation status in the BM lesions, vice versa.Moreover, EGFR mutations showed no significant effect onthe PFS and OS in the NSCLC patients with BM. However,well-controlled prospective studies with paired primaryNSCLC and BMs are needed to further validate the prognosticsignificance of EGFR mutation.

Conflicts of interest None

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Tumor Biol.