Metastatic brain tumors from non-small cell lung cancer with EGFR mutations: distinguishing influence of exon 19 deletion on radiographic features.

INTRODUCTION

Miliary brain metastasis is a rarity and refers to the presence of numerous small tumors in a perivascular distribution without intraparenchymal invasion and focal edema. Although the presence of epidermal growth factor receptor (EGFR) mutation and good response to gefitinib have been reported in non-small cell lung cancer (NSCLC) patients with miliary brain metastases, the influence of the EGFR mutations on the radiographic features remains unclear.

PATIENTS AND METHODS

All NSCLC patients with synchronous brain metastases detected at the time of a new diagnosis of NSCLC from March 2005 through May 2011 were divided according to EGFR mutation status. The number of brain tumors, size of the largest brain tumors, and size of peritumoral brain edema were compared among the groups.

RESULTS

Fifty-seven patients who met the criteria were divided into three groups: wild-type EGFR group (31 patients), exon 19 deletion group (18 patients), and exon 21 point mutation group (8 patients). The exon 19 deletion group had more multiple and smaller brain tumors with smaller peritumoral brain edema than did the wild-type group (P = 0.024, P = 0.0016, and P = 0.0036, respectively). The exon 21 point mutation group showed no significant difference in any of the radiographic values when compared with the wild-type group.

CONCLUSION

Our results indicate that NSCLC patients with the exon 19 deletion have such a peculiar pattern of brain metastases as multiple small metastases with small brain edema. This metastatic pattern may be similar to that of miliary brain metastases. Because it is unclear whether or not severe neurologic symptoms develop during their clinical courses like miliary brain metastases, regular evaluation with brain magnetic resonance imaging (MRI) should be considered, regardless of the presence of neurologic symptoms. Accumulation of knowledge about specific pattern of brain metastasis will help approach to "individual" management.