Modified OPTIModel with oligometastatic disease for the prediction of overall survival of patients with renal cell cancer and symptomatic long bone metastases

Aims: For patients with long bone metastasis (LBM), we have previously developed OPTIModel. In this study, we investigated whether the OPTIModel could be improved for patients with metastatic renal cell cancer (mRCC) by including oligometastatic bone metastases (OBM) as a risk factor. Methods: Patients with mRCC and symptomatic LBMs were included in a retrospective and prospective multicenter cohort. Bone metastases (BMs) were categorized as: solitary (SBM), limited BMs (2–4 BMs) or diffuse BMs (DBM; >4 BMs). OBM were defined as ≤ 4 BMs. Overall survival was estimated using Kaplan Meier method. Effect of risk factors on overall survival were assessed using multivariate Cox regression model. Based on these results, the OPTIModel was modified. To assess the discriminatory ability, Harrell's C-statistic was used. Results: 178 patients were included. Overall, median overall survival was 12.1 months (95 % confidence interval (CI): 8.8–15.3). Median survival for SBM (n = 53, 29.8 %), limited BMs (n = 60, 33.7 %) and DBMs (n = 65, 36.5 %) was 19.6 months (95 %CI: 6.8–32.4), 14.8 months (95 %CI: 7.6–21.9) and 6.1 months (95 %CI: 2.7–9.5), respectively. Median survival was 16.3 months (95 %CI: 10.6–22.0) in patients with OBM (n = 113, 63.5 %), with a hazard ratio of 2.11 (95 %CI: 1.44–3.09) compared to patients with DBM. Including OBM in the OPTIModel for mRCC improved C-statistic from 0.585 (standard error (SE) = 0.027) to 0.618 (SE = 0.024). Conclusion: Both SBM and limited BMs were associated with a longer overall survival in patients with mRCC and symptomatic LBMs. The modified OPTIModel for mRCC with inclusion of oligometastatic disease could guide decisions about local treatment of symptomatic LBMs.