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Published on: August 31, 2022
Time-dependent dose-response relation for absence of vaginal elasticity after gynecological radiation therapy
Eleftheria Alevronta1, Elisabeth Åvall-Lundqvist2, Massoud Al-Abany3
1Department of Oncology-Pathology, Division of Clinical Cancer Epidemiology, Karolinska Institutet, Stockholm, Sweden; Department of Oncology, Institute of Clinical Sciences, Division of Clinical Cancer Epidemiology, Sahlgrenska Academy, Gothenburg, Sweden.
Background And Purpose:
To investigate the dose-response relation between the dose to the vagina and the patient-reported symptom 'absence of vaginal elasticity' and how time to follow-up influences this relation.
Material And Methods:
The study included 78 long-term gynecological cancer survivors treated between 1991 and 2003 with external beam radiation therapy. Of those, 24 experienced absence of vaginal elasticity. A normal tissue complication model is introduced that takes into account the influence of time to follow-up on the dose-response relation and the patient's age. The best estimates of the dose-response parameters were calculated using Probit, Probit-Relative Seriality (RS) and Probit-time models. Log likelihood (LL) values and the Akaike Information Criterion (AIC) were used to evaluate the model fit.
Results:
The dose-response parameters for 'absence of vaginal elasticity' according to the Probit and Probit-time models with the 68% Confidence Intervals (CI) were: LL=-39.8, D50=49.7 (47.2-52.4) Gy, γ50=1.40 (1.12-1.70) and LL=-37.4, D50=46.9 (43.5-50.9) Gy, γ50=1.81 (1.17-2.51) respectively.
Conclusions:
The proposed model, which describes the influence of time to follow-up on the dose-response relation, fits our data best. Our data indicate that the steepness of the dose-response curve of the dose to the vagina and the symptom 'absence of vaginal elasticity' increases with time to follow-up, while D50 decreases.
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