Cell-targeted 114Inm and drug (BCNU) combination therapy in a rat acute lymphoblastic leukaemia

A proportion of syngeneic female rats inoculated intramuscularly with a lethal T-cell lymphoblastic (Roser) leukaemia are cured by a single intraperitoneal injection of bischloroethylnitrosourea (BCNU) (Carmustine) (10 mg kg-1) given towards the end of the preleukaemic phase (day 7). Additional therapy on day 4, using intravenous leukaemia cells lethally labelled with the radionuclide 114Inm, enhanced the overall cure rate by 30%. The spleen is a major site of indium concentration from the targeting cells so that the continuous local radiation field appears to result in a substantial reduction of the body load of leukaemia cells in the enlarged spleen particularly, thus enhancing the curative potential of the drug. The results demonstrate in principle that in patients in remission a single dose of targeted radiotherapy in the spleen combined sequentially with an appropriate drug might provide considerable aid in eliminating a residual population of leukaemia cells.