Can the Katagiri scoring system predict prognosis for surgically-managed patients with metastatic bone disease?

Background: The Katagiri scoring system is used extensively to predict survival for patients with metastatic bone disease. However, this system was initially formulated using a cohort largely comprised of patients managed non-operatively. Moreover, it is unclear whether surgery can impact or alter the survival of patients with metastatic bone disease. In this study, we sought to validate the Katagiri scoring system using a cohort of diverse surgically managed patients as well as to investigate the impact of surgical intervention on their outcome. Methods: We asked (I) what is the survival rate for each risk group in our cohort of surgically-managed patients? (II) Do surgically-managed patients exhibit improved survival compared with medically-managed patients with similar Katagiri scores? We retrospectively reviewed a cohort of patients who underwent surgical management for metastatic bone disease at a single institution over a 10-year period. Patients were divided into low-risk (score 1-3), intermediate-risk (score 4-6), and high-risk (score 7-10) groups based on their Katagiri score. The length of survival was recorded after surgical management. Survival at 6, 12, and 24 months was compared with those originally reported by Katagiri's cohort. Results: One hundred and eighty-three surgically treated patients were identified. Survival for low-risk surgically-treated patients was 83.3%, 71.8%, and 43.6% compared with 97.9%, 91.5% and 77.2% for the Katagiri cohort at 6, 12, and 24 months respectively (P=0.0004, P=0.0014, and P=0.0001 respectively). Survival for intermediate-risk surgically-treated patients was 64.1%, 43.6%, and 30.1% compared with 73.9%, 49.2%, and 27.6% for the Katagiri cohort at 6, 12, and 24 months respectively (P=0.08, P=0.63, and P=0.57 respectively). Survival for high-risk surgically-treated patients was 70.1%, 50.0%, and 29.2% compared with 27.2, 6.1%, and 2.2% for the Katagiri cohort at 6, 12, and 24 months respectively (P<0.001, P<0.001, and P<0.001 respectively). Conclusions: The Katagiri scoring system predicts survival well for surgically-managed patient within the intermediate-risk group. However, it underestimates the survival of surgically-managed patients in the high-risk group and overestimates the survival of surgically-managed patients in the low-risk group. Current findings suggest that high-risk patients may have improved outcomes as a result of surgical intervention, while low-risk patients realize improved outcomes with non-operative management. Level of evidence: Level III, retrospective study.