Tumor Burden and Intraosseous Metabolic Activity as Predictors of Bone Marrow Failure during Radioisotope Therapy in Metastasized Prostate Cancer Patients

Rationale. Radium-223-Dichloride (Ra-223) is an alpha-emitter, used to treat bone metastases. Patients with high metastatic burden and/or with increased trabecular bone uptake could present a higher incidence of hematologic toxicity. We hypothesized that these two factors are predictors of bone marrow failure. Material and Methods. A computer algorithm discriminated between trabecular bone () and tumor metastases () within pretherapeutic whole-body skeletal SPECT/CT (). The program calculated the metastatic invasion percent (INV%) as the ) ratio and extracted the mean counts. counts were correlated to % drop of hemoglobin (Hb), leukocytes (WBC), and platelets (PLT) after 3/6 Ra-223 cycles. Patient-specific and computational-derived parameters were tested as predictors of hematologic toxicity with MANOVA. Results. counts correlated with drop of Hb ( = 0,65, ) and PLT ( = 0,45, ). Appendicular counts showed a better correlation (, , and for Hb, WBC, and PLT, resp.). INV% directly correlated with counts ( = 0.68, ). At MANOVA, grade III/IV toxicity was predicted by INV% (), by long-bone invasion (), and by counts (). Conclusions. In patients with significant bone tumor burden, degree of bone invasion and trabecular bone uptake are predictors of subsequent bone marrow failure.

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