Figure 1.

Demonstration of the mathematical analysis of tumor growth and treatment. Data points are actual values obtained for a 9L tumor treated with a 2 × LD₁₀ BCNU dose. The line marked A is the least-squares fit of the pretreatment growth points to Eq. 1. The line marked C is the fit of the posttreatment growth points. Line C is extrapolated back to the time of treatment to give V_post. Log cell kill is the log of the ratio V_pre/V_post (Eq. 2). The line marked B is the theoretical tumor regrowth curve assuming Td_post = Td_pre. The relative contributions of cell kill and tumor growth rates are related to the calculated repopulation intervals, Tra_pre and Tra_post, as described by Eqs. 3 and 4. Tx, point of BCNU administration; Tra_pre, repopulation interval given equivalent pretreatment and posttreatment growth rates; Tra_post, repopulation interval given the fitted posttreatment growth rate; V_pre, tumor volume at Tx; V_post, theoretical “viable” tumor volume immediately after treatment determined by extrapolation of C.