Prospective evaluation of hydrogel use in gynecologic brachytherapy

To evaluate hydrogel visualization as a marker on CT and MR imaging and consider any potential dosimetric effects incurred by placement of the marker on brachytherapy for the treatment of gynecologic malignancies.

This prospective cohort study enrolled 25 patients with gynecologic cancers who underwent brachytherapy at Johns Hopkins Hospital. MR and CT imaging were used to compare TraceIT^TM hydrogel visualization immediately after placement with the brachytherapy applicator in place. Rectal dosimetric data of a 2 cm3 volume (D2cc) and equi-effective doses of 2 Gy fractions (EQD2) were obtained. For patients with data collected before and after spacer placement, a comparative analysis was conducted to assess the impact of the marker on rectal dose.

Hydrogel was safely injected into the space between the rectum and vagina in 25 patients, with no side effects related to gel placement. When comparing the agreement in gel visualization by 2 interpreters, inter-rater reliability (kappa statistic) was calculated and showed 58.3% (moderate) agreement (p = 0.0007). In patients who received a brachytherapy fraction both before and after TraceIT^TM placement, the average rectal displacement was 1.33 cm. The change in EQD2 D2cc rectum was significantly lower, with an average pre-TraceIT^TM dose of 5.02 Gy and a post-TraceIT^TM average of 4.60 Gy (p = 0.002).

Hydrogel placement is feasible during brachytherapy procedures for the treatment of gynecologic malignancies. Using TraceIT^TM as a marker resulted in better visualization on MR than on CT. Displacement significantly reduced the D_2cc to the rectum. Further research is needed to determine the optimal amount of hydrogel for spacing in gynecologic cancer patients.