Radioimmunotherapy with alpha-particle emitters: Microdosimetry of cells with a heterogeneous antigen expression and with various diameters of cells and nuclei

Intercellular variations in the level of antigen expression and in cellular and nuclear radii were taken into account in a model used to estimate cell survival for an in vitro experiment with antibodies containing cu-particle emitters that target the cell surface. Using measured variations in these characteristics for cells of two human cancer cell lines, the model gave re sults for cell survival and the fundamental parameter of radiation sensitiv ity, z(0), that differ substantially from those obtained using only mean va lues. The cell survival may be underestimated by a factor of 100 if only me an values of these cellular parameters are used, and calculated values of z (0) may be overestimated by a factor of 2, Most of this effect stems from t he variation in antigen expression, The magnitudes of the differences were found to be a function of the fractions of mean specific energy delivered b y surrounding activity and by activity bound to the cells. (C) 2001 by Radi ation Research society.