Natural history of bone-only metastasis in renal cell carcinoma.

Background: Bone metastasis (BM) is considered a poor prognostic factor of renal cell carcinoma (RCC). Confusion exists regarding how to deal with RCC patients with bone-only metastasis.

Patients And Methods: The clinical data of consecutive RCC patients with bone-only metastasis at Peking University Cancer Hospital between 2006 and 2018 were retrospectively collected and analyzed.

Results: Fifty-four eligible patients were screened from an RCC database of 1,878 metastatic patients. After a median follow-up of 43.6 m, 61.1% of the patients were presented with progression of prior BM or new BM. The progression-free survival (PFS) and overall survival (OS) was 16.2 m (95%CI: 11.4-21.0) and 65.2 m, respectively. For the 30 patients with oligo-metastasis (≤3 loci) and 24 ones with multiple-metastasis (>3 loci), the median OS was not reached and 42.0m (95%CI: 12.7-71.2) with statistical difference (P < 0.001). In the oligo-metastasis group, the median PFS of the 15 patients treated with local therapy and of the 13 patients treated with systemic therapy was 14.2 m (95%CI: 5.3-23.3) and 18.0 m (95%CI:15.4-20.6), respectively. In the multiple-metastasis group, the median PFS and OS of the 18 patients treated with systemic therapy was 16.6 m (95%CI: 7.5-25.7) and 63.9 m (95%CI: 21.8-106.0), respectively. Univariate analysis and multivariate analysis showed that the number of metastatic sites (oligo/multiple) and International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) score, RCC pathological subtype were significantly associated with prognosis (P < 0.05).

Conclusion: RCC patients with bone-only metastases have a favorable prognosis. The number of metastatic sites, IMDC, RCC pathological subtype could serve as survival predictors, which might provide clue of treatment modality.