Incorporating biologic measurements (SF2, CFE) into a tumor control probability model increases their prognostic significance: A study in cervical carcinoma treated with radiation therapy

Purpose: To assess whether incorporation of measurements of surviving fract ion at 2 Gy (SF2) and colony-forming efficiency (CFE) into a tumor control probability (tcp) model increases their prognostic significance. Methods and Materials: Measurements of SF2 and CFE were available from a st udy on carcinoma of the cervix treated with radiation alone. These measurem ents, as well as tumor volume, dose, and treatment time, were incorporated into a Poisson tcp model (tcp(alpha,rho)). Regression analysis was performe d to assess the prognostic power of tcp(alpha,rho) vs. the use of either tc p models with biologic parameters fixed to best-fit estimates (but incorpor ating individual dose, volume, and treatment time) or the use of SF2 and CF E measurements alone. Results: In a univariate regression analysis of 44 patients, tcp(alpha,rho) was a better prognostic factor for both local control-and survival (p < 0. 001 and p = 0.049, respectively) than SF2 alone (p = 0.009 for local contro l, p = 0.29 for survival) or CFE alone (p = 0.015 for local control, p = 0. 38 for survival). In multivariate analysis, tcp(alpha,rho) emerged as the m ost important prognostic factor for local control (p < 0.001, relative risk of 2.81). After allowing for tcp(alpha,rho), CFE was still a significant i ndependent prognostic factor for local control, whereas SF2 was not. The se nsitivities of tcp(alpha,rho) and SF2 as predictive tests for local control were 87% and 65%, respectively. Specificities were 70% and 77%, respective ly. Conclusions: A Poisson tcp model incorporating individual SF2, CFE, dose, t umor volume, and treatment time was found to be the best independent progno stic factor for local control and survival in cervical carcinoma patients. (C) 2001 Elsevier Science Inc.