Interfraction Variation and Dosimetric Changes in Patients With Cervical Cancer Treated With Intracavitary Brachytherapy

Abstract

PurposeIntracavitary brachytherapy is integral in the treatment of cervical cancer. Because of interfraction variation, the current standard is replanning with every fraction. This study aimed to determine whether there was a difference in relative dosimetry if the source position and dwell time of the first fraction were applied to subsequent fractions.Materials and MethodsThe authors performed a retrospective review of charts and films from 2007 to 2012. Eligible cases were patients with cervical cancer treated with brachytherapy with the same dose prescription to point A. Replanning was done on the first set of orthogonal plates. Source position and dwell time were subsequently applied to the remaining fractions using actual films.ResultsTwenty-nine patients were included in this study. The results showed that cervical, rectal, and bladder dose between the actual plan and the hypothetical plan were not statistically different. In the hypothetical plan, the source activity and dwell time of the first plan were applied to the orthogonal films of the subsequent fractions and showed no significant difference in all dose points.ConclusionThe results of this study showed proof of concept of the safety of using the source position and dwell time of the first plan for subsequent fractions. Until further studies are performed (also using three-dimensional planning software), the concept should be considered investigational because of the small sample size of the study. Until such research is performed, it is still strongly recommended that replanning be performed with every fraction whenever it is feasible.

Dosimetric changes and interfraction anatomical variations during high dose rate brachytherapy of cervical cancers- Can replanning be avoided?

“…Garipagaoglu et al showed a significant variation in the interfraction position of applicators accounting for different doses delivered to the bladder and rectal tissues, but with no remarkable differences in the radiobiological effective doses 11 whereas the study by Jason et al in his recent retrospective review of 29 patients, showed evidence of the safely considering the first plan using the same source position and dwell time for the subsequent fractions but however do not currently recommend it as a standard of care. 12 This study with a sample size of 133 patients, convey that when the source position and dwell time of the first implemented fraction plan when applied to the subsequent second and third brachytherapy applications, there is a statistically significant difference between the doses received to the point B, rectum and bladder points, which necessitates replanning for every session of brachytherapy. The results of this study is in accordance to the current American Brachytherapy Society recommendation for replanning with every fraction.…”

“…Jason et al in his recent retrospective review of 29 patients, showed the proof of safely considering the first plan for the subsequent fractions using same source position and dwell time but however do not currently recommend it as a standard of care. 12 Our study aimed to determine the correlation of interfraction variations in positioning of applicator and its relationship with relative dosimetry if the dwell time and source positions of the plan of first fraction were applied to other subsequent fractions.…”