Rapid intracranial response to osimertinib, without radiotherapy, in nonsmall cell lung cancer patients harboring the EGFR T790M mutation: Two Case Reports

Abstract

Rationale: Most of nonsmall cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) activating mutations eventually acquire resistance to the first EGFR-tyrosine kinase inhibitors (TKIs) therapy after varying periods of treatment. Of note, approximately one-third of those patients develop brain metastases, which deteriorate their quality of life and survival. The effect of systemic chemotherapy on brain metastases after acquisition of EGFR-TKI resistance is limited, and thus far, whole-brain radiation therapy, which may cause the harmful effect on neurocognitive functions, has been the only established therapeutic option for especially symptomatic brain metastases. Osimertinib is a third-generation oral, potent, and irreversible EGFR-TKI. It can bind to EGFRs with high affinity even when the EGFR T790M mutation exists in addition to the sensitizing mutations. Its clinical efficacy for NSCLC patients harboring the T790M mutation has already been shown; however, the evidence of osimertinib on brain metastases has not been documented well, especially in terms of the appropriate timing for treatment and its response evaluation.

Patient concerns, diagnoses, and interventions: We experienced 2 NSCLC patients with the EGFR T790M mutation; a 67-year-old woman with symptomatic multiple brain metastases administered osimertinib as seventh-line chemotherapy, and a 76-year old man with an asymptomatic single brain metastasis administered osimertinib as fifth-line chemotherapy.

Outcomes: These patients showed great response to osimertinib within 2 weeks without radiation therapy.

Lessons: These are the first reports to reveal the rapid response of the brain metastases to osimertinib within 2 weeks. These cases suggest the possibility that preemptive administration of osimertinib may help patients to postpone or avoid radiation exposures. In addition, rapid reassessment of the effect of osimertinib on brain metastases could prevent patients from being too late to receive essential radiotherapy.

Figure 1

Contrast-enhanced axial brain CT images of case 1. Multiple metastases at baseline. Complete remission of brain metastases except for 1 (white allow) in the left frontal lobe after 13 days osimertinib administration. CT = computed tomography.

Figure 2

Chest x-rays of case 1. Shrinkage of the right pulmonary nodule after 5 days osimertinib administration.

Figure 3

Contrast-enhanced axial brain CT images of case 2. Complete remission of a single brain metastasis (white allow) in the right parietal lobe after 10 days osimertinib administration.

Figure 4

Chest x-rays and axial chest CT images of case 2. Decrease of pleural effusion and shrinkage of pulmonary nodules on chest x-rays after 14 days osimertinib administration. Shrinkage of multiple lung metastases and decrease of left-sided pleural effusion on chest CT images after 31 days osimertinib administration.