Bone Metastasis of Non-Small-Cell Lung Cancer Showing Pathological Complete Response to Osimertinib Monotherapy

A 70-year-old man with lung adenocarcinoma had undergone right lower lobectomy and lymph node dissection. Only 6 months later under adjuvant uracil and futraful therapy, the patient developed a solitary bone metastasis in the right 8th rib. Due to positive mutation of epidermal growth factor receptor (EGFR) exon 21 L858R in the primary cancer, the patient received osimertinib monotherapy, leading to massive calcification of the osteolytic bone metastasis with significant decrease of standard uptake value on positron emission tomography. After 12 months of osimertinib monotherapy, slight enlargement of the ground glass nodule, i.e., presumed noninvasive lung cancer, in the right upper lobe, and no further occurrence of metastatic foci made us to resect both the lung nodule and the bone metastasis. Pathological examination showed the lung nodule to be noninvasive adenocarcinoma and the bone metastasis to have no viable cancer cells. The patient was discharged on the 8th postoperative day without any complication. On developing a therapeutic strategy for advanced/recurrent EGFR mutation-positive lung adenocarcinoma, oncologists should note the possibility of pathological complete response to newly developed EGFR tyrosine kinase inhibitors including osimertinib for a presumed cure of oligometastatic lung adenocarcinoma.