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 ( = 47). 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, < 0.01) and PLT ( = 0,45, < 0.01). Appendicular counts showed a better correlation ( < 0.05, < 0.01, and < 0.001 for Hb, WBC, and PLT, resp.). INV% directly correlated with counts ( = 0.68, < 0.001). At MANOVA, grade III/IV toxicity was predicted by INV% ( < 0.01), by long-bone invasion ( < 0.005), and by counts ( < 0.05).

Conclusions: In patients with significant bone tumor burden, degree of bone invasion and trabecular bone uptake are predictors of subsequent bone marrow failure.