Evaluation of Bone Scan Index as a Prognostic Tool in Breast Cancer Patients with Bone Metastasis

Background: Bone metastatic involvement represents a leading cause of death in patients with advanced breast cancer (BC). At present, it is not clear whether the bone metastatic load might impact Overall Survival (OS) in patients with bone metastatic BC at diagnosis. For this purpose, we used the Bone Scan Index (BSI), which is a reproducible and quantitative expression of tumor load observed at bone scintigraphy. Objective: The aim of this study was to associate BSI with OS in bone metastatic BC patients. Methods: In this retrospective study, we enrolled BC patients with bone metastases at the scintigraphic bone scan performed for staging purposes. The BSI was calculated through the DASciS software, and statistical analysis was carried out. Other clinical variables relevant to OS analysis were taken into account. Results: Of a total of 94 patients, 32% died. In most cases, the histotype was ductal infiltrating carcinoma. The median OS from diagnosis was 72 months (CI 95%: 62-NA). The univariate analysis with COX regression showed that only hormone therapy significantly correlates with OS (HR 0.417, CI 95%: 0.174-0.997, p < 0.049). As concerning BSI, the statistical analysis showed that it does not predict OS in BC patients (HR 0.960, 95% CI: 0.416-2.216, p < 0.924). Conclusion: Although the BSI significantly predicts OS in prostate cancer and in other tumors, we observed that the metastatic load of bone disease has not a key role in prognostic stratification in our population.