IMAGING FOR IMPROVED PREDICTION OF MYELOTOXICITY AFTER RADIOIMMUNOTHERAPY

BACKGROUND. The severity of myelotoxicity after radioimmunotherapy has been predicted from body and blood radiation doses to marrow. However , marrow radiation can be increased substantially if the marrow or ske leton contains the malignancy targeted by the radiolabeled monoclonal antibodies. A study of 29 patients treated with iodine-131 (I-131)-Lym -1 showed that radiation doses to marrow from body and blood had littl e correlation with myelotoxicity. The purpose of the present study was to assess the significance of marrow targeting and other factors for prediction of myelotoxicity. METHODS. Injected radioactivity and nonta rgeted radiation doses to marrow were compared with peripheral blood c ell counts after the first therapy dose of I-131-Lym-1 in 16 heavily p retreated patients with non-Hodgkin's lymphoma (NHL). Bone marrow biop sy, targeted marrow radiation doses, marrow image uptake scores, age, Kamofsky performance score (KPS), previous chemotherapy, and tumor bur den were also compared with blood counts. RESULTS. Myelotoxicity was n ot predicted well by injected radioactivity, total body radiation, or body and blood radiation doses contributed to marrow (P > 0.1). Biopsy -proven bone marrow lymphoma also failed to predict myelotoxicity (P > 0.1). Thrombocytopenia and leukopenia were predicted well by targeted radiation dose to marrow (P < 0.05) obtained by I-131 imaging. Simila rly, marrow image scores predicted decreases in platelets and white bl ood cells (WBCs; P < 0.05). Prediction of myelotoxicity using marrow r adiation dose methods was slightly improved when serum lactic dehydrog enase (LDH), age, KPS, and prior chemotherapy were included in the ana lysis (P less than or equal to 0.01). CONCLUSIONS. Prediction of myelo toxicity was improved in this group of patients by assessment of the t argeting component of marrow radiation and was better predicted and ob tained more easily by semiquantitative marrow image scores. Further im provement in prediction was slight when other factors were considered. (C) 1997 American Cancer Society.