Fluorine-18-fluorocholine PET/CT parameters predictive for hematological toxicity to radium-223 therapy in castrate-resistant prostate cancer patients with bone metastases: a pilot study

PURPOSE: This study aims to predict hematological toxicity induced by (223)Ra therapy. We investigated the value of metabolically active bone tumor volume (MBTV) and total bone lesion activity (TLA) calculated on pretreatment fluorine-18-fluorocholine ((18)F-FCH) PET/CT in castrate-resistant prostate cancer (CRPC) patients with bone metastases treated with (223)Ra radionuclide therapy. PATIENTS AND METHODS: (18)F-FCH PET/CT imaging was performed in 15 patients with CRPC before treatment with (223)Ra. Bone metastatic disease was quantified on the basis of the maximum standardized uptake value (SUV), total lesion activity (TLA=MBTV×SUV(mean)), or MBTV/height (MBTV/H) and TLA/H. (18)F-FCH PET/CT bone tumor burden and activity were analyzed to identify which parameters could predict hematological toxicity [on hemoglobin (Hb), platelets (PLTs), and lymphocytes] while on (223)Ra therapy. Pearson’s correlation was used to identify the correlations between age, prostate-specific antigen, and (18)F-FCH PET parameters. RESULTS: MBTV ranged from 75 to 1259 cm(3) (median: 392 cm(3)). TLA ranged from 342 to 7198 cm(3) (median: 1853 cm(3)). Patients benefited from two to six cycles of (223)Ra (n=56 cycles in total). At the end of (223)Ra therapy, five of the 15 (33%) patients presented grade 2/3 toxicity on Hb and lymphocytes, whereas three of the 15 (20%) patients presented grade 2/3 PLT toxicity. Age was correlated negatively with both MBTV (r=−0.612, P=0.015) and TLA (r=−0.596, P=0.018). TLA, TLA/H, and MBTV/H predicted hematological toxicity on Hb, whereas TLA/H and MBTV/H predicted toxicity on PLTs at the end of (223)Ra cycles. Receiver operating characteristic curve analysis allowed to define the cutoffs for MBTV (915 cm(3)) and TLA (4198 cm(3)) predictive for PLT toxicity, with an accuracy of 0.92 and 0.99. CONCLUSION: Tumor bone burden calculation is feasible with (18)F-FCH PET/CT with freely available open-source software. In this pilot study, baseline (18)F-FCH PET/CT markers (TLA, MBTV) have shown abilities to predict Hb and PLT toxicity after (223)Ra therapy and could be explored for patient selection and treatment optimization.