Osteoblastic Response in Patients with Non-small Cell Lung Cancer with Activating EGFR Mutations and Bone Metastases during Treatment with EGFR Kinase Inhibitors

Frequently, treatment of patients with non-small cell lung cancer with tyrosine kinase inhibitors is stopped because of new or progressive bone metastases. Osteoblastic response is considered a healing reaction during effective systemic therapy, defined by osteoblastic demarcation of preexisting or “new” bone lesions, whereas disease response can be identified in other tumor locations. 1 In this study, we describe three patients with non-small cell lung cancer harboring sensitizing epidermal growth factor receptor (EGFR) mutations with osteoblastic responses during disease control by tyrosine kinase inhibitor treatment. PATIENT 1 This 47-year-old woman, former smoker, was diagnosed with stage IV adenocarcinoma (EGFR exon19 del) of the lung with pulmonary, hepatic, and osseous metastases. After five cycles of platinum-containing chemotherapy plus radiotherapy (right shoulder, thoracic spine, and both femurs), progressive hepatic and osseous metastasis occurred. Gefitinib was started, and 8 weeks later, computed tomography (CT) confirmed a partial response in lung and liver. Simultaneously, progressive demarcation of a preexisting osteoblastic lesion in the left iliac bone could be identified as possible sign of response (Figures 1A, B). Six months later, when progressive disease was diagnosed in lung, liver, and axillary lymph nodes, the lesion in the left iliac bone showed less sclerosis and more lytic areas (Figures 1B, C).