2795 - Evaluating Statistical Cure Probability and Cure Time in Cervical Cancer Patients Based on a Mixture Cure Model

Purpose/Objective(s): The primary objective of this study was to evaluate the relative survival (RS) of cervical cancer patients using a mixture cure model, comparing them to a matched general population. The model assumes two groups: cured (with no excess risk) and uncured. A plateau in the RS curve indicates a cure, with the plateau corresponding to the cure fraction. This study aims to determine whether cervical cancer patients achieve statistical cure following definitive chemoradiotherapy and to estimate the time to cure based on both mortality and disease progression.

Materials/Methods: We conducted a retrospective analysis of 1,434 cervical cancer patients diagnosed between 2005 and 2016 received definitive (chemo) radiotherapy. After excluding patients with incomplete baseline data, the final cohort included 1,209 patients. Mixture cure models were fitted using a Weibull distribution and logistic link, with mortality and progression as events for the uncured group. Background mortality was adjusted by matching patients to a general population based on age, sex, and year of diagnosis. The cure fraction, representing the proportion of patients with no excess risk of death compared to the general population, was estimated by identifying the plateau in the RS curve, as indicated by the logistic component of the model. Cure time, defined as the time from treatment initiation until 95% of uncured patients experienced the event, was calculated using the survival distribution for the uncured group. All statistical analyses were performed using STATA and R.

Results: When mortality was considered as the uncured event, the cure fraction was estimated to be 79.9%, with a cure time of 7.62 years. Significant factors associated with a lower probability of cure included non-squamous histology (p<0.001), tumor size =4 cm (p<0.001), para-aortic lymph node metastasis (p<0.001), and FIGO stage =III (p<0.001); however, pelvic lymph node metastasis was not significantly associated (p=0.119). When progression was considered as the uncured event, the cure fraction was 74.3%, with a cure time of 4.85 years. Significant factors included non-squamous histology (p<0.001), tumor size =4 cm (p<0.001), para-aortic lymph node metastasis (p<0.001), and FIGO stage =III (p=0.002); pelvic lymph node metastasis was again non-significant (p=0.056). RS curves showed a plateau, confirming the model’s fit.

Conclusion: This study demonstrates that cervical cancer patients can achieve statistical cure after chemoradiotherapy, with cure fractions of 79.9% (mortality as the uncured event, cure time: 7.62 years) and 74.3% (progression as the uncured event, cure time: 4.85 years). Factors that significantly reduce the likelihood of cure include non-squamous histology, larger tumor size, para-aortic lymph node metastasis, and advanced FIGO stage. These findings, enriched with cure time estimates, address an important gap in the literature and support the efficacy of chemoradiotherapy in treating cervical cancer.