Impact on treatment time of MRI-based brachytherapy in two implants (4 doses) compared with CT-based brachytherapy in five implants for cervical cancer.

Purpose: Concurrent chemoradiotherapy and brachytherapy is the standard of care for locally advanced cervical cancer. Brachytherapy is an integral part of treatment and has improved overall survival. Research is needed to ascertain the planning modalities and schedules to best use resources and optimize treatment time course. We hypothesized that MRI-based brachytherapy when delivered with the described regimen would not prolong, and potentially shorten, overall treatment time as compared with CT-based brachytherapy.

Methods And Materials: This study was a single-institution retrospective review within the years 2008 through 2018. Patients with cervical cancer of any stage who underwent definitive chemoradiotherapy and either CT- or MRI-based brachytherapy were included. The primary outcome variable for this study was time (in days). Overall treatment time was defined as the number of days from the first until the last day of radiotherapy. Univariate analysis was performed using Stata statistical software.

Results: External beam radiotherapy doses were generally 45-50.4 Gy. CT-based and MRI-based brachytherapy were performed in 55 and 49 patients, respectively. The median treatment time for brachytherapy with CT-based planning was 19.0 days and with MRI-based planning was 9.0 days (p < 0.001). The median treatment time for total radiation therapy with CT-based planning was 53 days, and with MRI-based planning was 50 days (p = 0.781).

Conclusions: This study found that MRI-based brachytherapy, when performed with the proposed regimen, did not prolong overall treatment time and significantly decreased time to complete brachytherapy in comparison with CT-based brachytherapy on nonconsecutive days. This regimen favorably impacts timely completion of treatment and uses MRI resources well within the construct of our institution.