Osteosclerotic change as a therapeutic response to gefitinib in symptomatic non-small cell lung cancer bone metastasis

BACKGROUND: Despite improvement in the overall survival of patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutation, the effects of EGFR tyrosine kinase inhibitor (EGFR-TKI) treatment on bone metastasis remain unclear. This study investigated radiological responses to gefitinib regarding bone metastasis in patients. METHODS: We treated 260 patients with NSCLC and symptomatic bone metastasis. Thirty-seven patients harboring EGFR mutation were treated with gefitinib for more than 30 days and followed up for more than 3 months (GEF group). We performed a retrospective observational study by selecting 36 cases without EGFR-TKI treatment, at least 3 months of follow-up, and at least two radiological evaluations as the control group. We assessed the best overall radiological response, interval from treatment initiation to appearance of a radiological response, and the local response maintenance rate. RESULTS: The best effect in the GEF group was 98% partial response or better, which was significantly higher than the 57% observed in the control group (p < 0.001). The GEF and control groups maintained 83% and 42% local response maintenance rates at one year, respectively (p < 0.001). In the GEF with radiotherapy group, the local response maintenance rate was maintained at 92% at 1 year, while in the GEF without RT group, there was a decrease in the local response maintenance rate from 270 days. CONCLUSION: Gefitinib treatment for bone metastases in patients harboring EGFR mutation resulted in a beneficial osteosclerotic change in most patients. Combined gefitinib and radiotherapy provide long-lasting local control of bone metastases.