Impact of Bone-Modifying Agents on Post-Bone Metastasis Survival Across Cancer Types.

Background: Bone metastasis is associated with a poor prognosis. Bone-modifying agents (BMA) are commonly used for the prevention or treatment of skeletal-related events (SRE) in patients with bone metastasis; however, whether or not treatment with BMA improves survival remains unclear. In this study, we investigated whether BMA was involved in post-bone metastasis survival.

Methods: A total of 539 cancer patients were retrospectively analyzed to identify significant independent factors in post-bone metastasis survival.

Results: Among the overall population, patients with the following cancers had a median survival longer than 24 months: thyroid, 97.2 months; breast, 51.5 months; prostate, 47.2 months; and kidney, 38.8 months. In contrast, median post-bone metastasis survival was significantly shorter in gastrointestinal (GI) (6.5 months), head and neck (6.3 months), and urinary tract (3.4 months) cancers. In non-small cell lung cancer (NSCLC), the log-rank test demonstrated that the epidermal growth factor receptor (EGFR) mutation was a significant factor for post-bone metastasis survival: EGFR mutation (-) = 67, median post-bone metastasis survival 11.5 months (95% CI: 6.0-15.2); EGFR mutation (+) = 39, median post-bone metastasis survival 28.8 months (95% CI: 18.1-35.7) ( < 0.05). Intriguingly, treatment with BMA was a significant positive prognostic factor: BMA (-) = 203, median post-bone metastasis survival 7.8 months (95% CI: 5.8-12.5); BMA (+) = 336, median post-bone metastasis survival 21.9 months (95% CI: 16.1-26.4) ( < 0.001). Moreover, the Cox proportional hazards model showed that this was particularly evident in cancer types with poor prognosis such as GI cancer (hazard ratio [HR]: 0.62, 95% CI: 0.40-0.95; < 0.05) and NSCLC without the epidermal growth factor receptor (EGFR) mutation (HR: 0.56, 95% CI: 0.34-0.91; < 0.05).

Conclusions: Treatment with BMA is recommended not only for the prevention and/or treatment of SRE, but also may have a positive impact on post-bone metastasis survival, particularly in cancers with typically poor post-bone metastasis survival such as GI cancer and NSCLC without the EGFR mutation.