A new hyaluronate gel spacer and injection technique for cervical cancer brachytherapy: a technical report

Spacers separating the tumor from adjacent organs help improve irradiation dose parameters. We introduce a new hyaluronate gel spacer with MEIJI (ADANT®) as an alternative to the previously used Suvenyl® and its injection technique for cervical cancer brachytherapy. Five patients with cervical cancer underwent hyaluronate gel injection (HGI) with the MEIJI hyaluronate gel in their rectovaginal and vesicovaginal septa. The minimum doses covering 90% of the high-risk clinical target volume (CTVHRD90%), the most exposed 2 cc (D2cc) of organs at risk per session, as well as the total doses for combined external beam radiotherapy (with a central shield) and brachytherapy, were assessed. The median CTVHRD90% was 9.3 (range, 6.4-9.7) Gy per session and 92.2 Gy in the equivalent dose in 2 Gy fractions (EQD2) (80.3-93.3 Gy-EQD2) overall. The median rectum D2cc was 2.9 (1.8-5.0) Gy per session and 45.4 (43.4-57.1) Gy-EQD2 overall. The median D2cc of the bladder (bladder D2cc) was 4.8 (2.4-6.5) Gy per session and 64.6 (62.3-69.6) Gy-EQD2 overall. The MEIJI spacer disappeared within 3 or 7 days with no adverse events associated with HGI or deterioration of the patients' quality of life. MEIJI HGI facilitates a sufficient CTVHRD90% while keeping the rectal and bladder D2cc within dose constraints, even when the rectum and bladder are in close proximity to the CTVHR. In conclusion, the MEIJI spacer may help appropriately meet dose constraints, thereby potentially contributing to improving local control and/or reducing adverse events for patients receiving radiotherapy for cervical cancer.