Prognostic Value of a Bone Marrow Scan Before and During Treatment of Bone Metastases With Radium-223-dichloride in Metastatic Castration-resistant Prostate Cancer

Background: Due to the risks of hematological side effects resp. clinical aggravation, not all patients with metastasized castration resistant prostate cancer (mCRPC) and bone metastases should undergo all six cycles of radium-223-dichloride therapy. A parameter helping us to assess the chances of successful therapy management as well as the risk of hematological side effects is needed. The aim of this study is to analyze “Bone Marrow Scintigraphy” (BMS) as a prognostic factor. Methods: 106 patients were included in our single-center study. 93 patients underwent BMS with 492-667 MBq Tc-99m Scintimun® prior to therapy. The “Uptake Ratio” (UR) was calculated by positioning “regions of interest” (ROI) around the sacroiliac region, the sternum and the background areas. We calculated an UR threshold value by means of a “Receiver-Operating-Characteristics” (ROC) curve. The UR and the “Bone Scan Index” (BSI), which is automatically gained by bone scintigraphy, were related and compared to other measured parameters (lab parameters, androgen deprivation therapy (ADT)). Statistics software IBM® SPSS® Statistics (Version 24.0) was employed to identify prognostic factors by univariate und multivariate analyzes.Results: The sacroiliac area-to-background technique proved helpful in combination with the calculated threshold UR=8 for quantitative assessment of a BMS. Radium-223-dichloride treatment showed significantly lower hematological toxicity at UR>8 (p=0.001). More precisely subdivided, there was a significant effect on to the number of erythrocytes (p=0.018), leucocytes (p=0.030) und neutrophil granulocytes (p=0.031). Significant prognostic factors influencing the “Overall survival” (OS) were the bone marrow (BM) distribution pattern (p=0.039) and the calculated UR (p=0.027). Conclusion: An UR value of 8 can be used for an approximation in prognostic assessment of risks and chances of this therapy. A combination of a qualitative and a quantitative evaluation of pre-therapeutic BMS could help to minimize therapy drop-outs and an avoidable exposure to radium-223-dichloride-therapy as well as other potential radio-nuclide therapies.