An analysis of the survival rate after radiotherapy in lung cancer patients with bone metastasis: is there an optimal subgroup to be treated with high-dose radiation therapy?

We investigated the prognostic factors after radiotherapy for bone metastasis from lung cancer while taking the recent findings in the treatment of such cases into consideration. A total of 132 patients with bone metastases from pathologically confirmed lung cancer were evaluated regarding the following potential prognostic factors: treatment for primary site (surgery vs. other), treatment site (spine vs. other), number of bone metastases (solitary vs. multiple), number of metastatic organs (0 vs. 1 vs. ≥2), neurological symptoms (no symptoms vs. numbness vs. paresis), degree of pain (no pain vs. mild pain vs. severe pain), performance status [PS] (0-1 vs. ≥2), biological effective dose [BED] (≥40 Gy vs. <40Gy), time to distant metastasis (≥1 year vs. <1 year), histology (adenocarcinoma vs. others), and use of epidermal growth factor receptor [EGFR]-targeted agents (Yes vs. No). The univariate analysis demonstrated that all factors except for the treatment site were significant. Surgery as treatment for primary site, solitary bone metastasis, no visceral organ metastasis, no symptoms or numbness, no pain, PS<2, BED≥40 Gy, time to distant metastasis ≥ 1year, adenocarcinoma histology, and use of EGFR-targeted agents were correlated with a favorable prognosis. In a multivariate analysis, solitary bone metastasis, PS<2, BED≥40 Gy, adenocarcinoma histology, and the use of EGFR-targeted agents were significantly correlated with a better survival (p = 0.038, 0.006, 0.003, 0.014, and <0.001, respectively). A contingency table to assess the relationship between each variable and the median survival time of the patients according to the administered BED showed that in patients with the time to distant metastasis ≥ 1year and the use of EGFR-targeted agents, the subgroups treated with BED≥40 Gy had a favorable prognosis. Our study suggests that high-dose radiotherapy is associated with a better prognosis in combination with other favorable prognostic factors.