Purpose: To analyze the effect of total treatment time on infield pelvic control and survival for squamous cell carcinoma of the uterine cervix using the combined 1973 and 1978 Patterns of Care (PCS) data base.
Methods and materials: Eight hundred thirty-seven evaluable patients were analyzed for the effect of total treatment time on outcome. The Kaplan-Meier method was used to estimate time-to-outcome annual rates. Comparisons of time to failure were performed with the log rank test. Multivariate analysis was performed using the Cox regression analysis.
Results: A highly significant decrease in survival (p = .0001) and pelvic control (p = .0001) was demonstrated as the total treatment time was increased from < 6, 6 to 7.9, 8 to 9.9, and 10+ weeks. Stage III accounted for the majority of the adverse effect from the prolongation of total treatment time. Multivariate analysis of total treatment time in addition to previously reported significant pretreatment and treatment factors from the PCS data base revealed three independent factors for infield recurrence, namely Stage I versus II versus III (p = .0001), total treatment time < 6 versus 6 to 7.9 versus 8 to 9.9 versus 10+ weeks (p = .003), and age > 50 versus < or = 50 years (p = .01). When the analysis was performed by stage to evaluate the effect of overall treatment time with respect to the extent of pelvic disease as defined by PCS, total treatment time continued to be an independent prognosticator for infield pelvic control (p = .01) and survival (p = .02) for Stage III but not Stages I and II.
Conclusion: This study demonstrates a significant adverse effect on survival and pelvic control with prolongation of the total radiation treatment time for Stage III squamous cell cancer of the uterine cervix in multivariate analysis. In the future design of clinical trials, limitations on total treatment time should be rigorously controlled, and the effect of variations in this important factor by altered fractionation schemes should be studied.