Bone scan index on bone scintigraphy and radiation therapy for bone metastases from cancers other than prostate and breast cancers: a retrospective observational study
Abstract Background A low bone scan index that is associated with a better prognosis in patients with bone metastases from prostate or breast cancer, the former often being osteolytic, has been established. In this study we aimed to use new automatic analysis software (VSBONE BSI; Nihon Medi-Physics, Tokyo, Japan) to investigate whether the pre-radiation therapy bone scan index, derived from bone scintigraphy images, is a prognostic indicator in patients undergoing radiation therapy for bone metastases from cancers other than breast or prostate cancer. Methods In this retrospective single institution study, we analyzed data of 51 patients who had undergone whole-body scintigraphy before receiving radiation therapy for bone metastases from cancers other than breast and prostate cancer between 2013 and 2019. Their bone metastases were classified as osteoblastic, osteolytic, or mixed and their pre-radiation bone scan indexes were automatically calculated using newly developed software (VSBONE BSI; Nihon Medi-Physics, Tokyo, Japan). Univariate and multivariate analyses were performed to identify associations between selected clinical variables and overall survival. Results We did not find a significant association between BSI and overall survival, possibly because osteolytic lesions may be underestimated by bone scan indexes. However, we did find that younger patients (aged less than the median of 66 years at the time of bone scintigraphy or of diagnosis of bone metastases) had significantly better overall survivals than older patients (P = 0.016 and P = 0.036, respectively). Additionally, bone scan indexes were significantly lower in patient with solitary or osteolytic bone metastases than in those with osteoblastic or mixed bone metastases (P = 0.035 and P = <0.001, respectively), and significantly higher in those with lung cancer than in those with other types of cancer (mean BSI 3.26% vs. 1.97%; P = 0.009). Conclusions The only significant association with survival identified in this study was for age at the time of bone scintigraphy and at time of diagnosis of bone metastases. In particular, we found no association between bone scan index and survival in the whole study cohort.