Can bone marrow scintigraphy predict platelet toxicity after treatment with 186Re-HEDP?

The toxicity of 186Re-1,1-hydroxyethylidene diphosphonate (186Re-HEDP) therapy in patients with painful bone metastases is mainly limited to thrombocytopaenia. The aim of this study was to investigate the influence of bone marrow scintigraphy on the prediction of decreased platelet counts after 186Re-HEDP therapy. Twenty-nine prostatic cancer patients with multiple painful bone metastases were included in the study. From a pre-therapy nanocolloid bone marrow scintigram, the bone marrow index (BMI) was determined as an indicator of the extent of bone marrow involvement. The influence of the BMI on the prediction of percent decrease in platelet counts was investigated. The mean BMI was 59 +/- 20. Regression analysis showed that the BMI does not improve the relationship between percent reduction in platelet count and administered dose. In contrast, we previously showed that the bone scan index (BSI) does predict the percent reduction in platelet counts before treatment. We conclude that bone marrow scintigraphy does not provide any additional information on platelet toxicity after a therapeutic dose of 186Re-HEDP. Bone scintigraphy is preferred in the prediction of reduced platelet counts.