Now is it time to implement spacers in cervical cancer brachytherapy?

Role of the gel spacer in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients

BACKGROUND

To protect the rectum and bladder from high dose exposure, the Japanese guidelines for managing uterine cervical carcinoma recommend pelvic irradiation with central shielding (CS). Conversely, the European Society for Radiotherapy and Oncology (ESTRO) and the American Brachytherapy Society (ABS) guidelines recommend delivering ≥85 Gy to high-risk clinical target volume D90 (CTVHR D90%). In this study, we investigated whether a gel spacer can enable the safe delivery of the ESTRO/ABS-recommended doses to the target while observing dose constraints for the OARs without using CS in external beam radiation therapy (EBRT).

MATERIALS AND METHODS

Twenty patients who received definitive radiation therapy without CS and were treated by brachytherapy with a gel spacer between 2017 and 2022 were retrospectively reviewed. The cumulative doses of EBRT and brachytherapy treatment outcomes and incidence of adverse events were also examined.

RESULTS

The median cumulative CTVHR D90%, rectum D2cm3, and bladder D2cm3 were 86.6 Gy, 62.9 Gy, and 72.0 Gy, respectively. The 2-year local control rate was 95%. There were no CTCAE ≥Grade 3 late gastrointestinal or genitourinary adverse events.

CONCLUSIONS

The use of gel spacer can enable ESTRO/ABS-recommended dose constraints even without using CS in EBRT, with favorable outcomes and low adverse event rates.

Effective timing of hyaluronate gel injection in image-guided adaptive brachytherapy for uterine cervical cancer: a proposal of the 'adjusted dose score'

Hyaluronate gel injection (HGI) in the rectovaginal septum and vesicovaginal septum is effective in the setting of high-dose-rate image-guided adaptive brachytherapy (IGABT) for cervical cancer. We aimed to retrospectively investigate optimal conditions for HGI to achieve optimal dose distribution with a minimum number of HGI. We classified 50 IGABT plans of 13 patients with cervical cancer who received IGABT both with and without HGI in the rectovaginal septum and vesicovaginal septum into the following two groups: plan with (number of plans = 32) and plan without (number of plans = 18) HGI. The irradiation dose parameters of high-risk clinical target volume (CTVHR) and organs at risk per fraction were compared between these groups. We also developed the adjusted dose score (ADS), reflecting the overall irradiation dose status for four organs at risk and CTVHR in one IGABT plan and investigated its utility in determining the application of HGI. HGI reduced the maximum dose to the most exposed 2.0 cm3 (D2.0 cm3) of the bladder while increasing the minimum dose covering 90% of CTVHR and the percentage of CTVHR receiving 100% of the prescription dose in one IGABT plan without causing any associated complications. An ADS of ≥2.60 was the optimum cut-off value to decide whether to perform HGI. In conclusion, HGI is a useful procedure for improving target dose distribution while reducing D2.0 cm3 in the bladder in a single IGABT plan. The ADS can serve as a useful indicator for the implementation of HGI.

Safe dose escalation and reduction of the fraction number of uterine cervical brachytherapy using a gel spacer in the rectovaginal and vesicouterine septum: A planning study

PURPOSE

To evaluate the possibility of dose escalation and reduction of fraction number in cervical brachytherapy using a gel spacer.

MATERIAL AND METHODS

Twenty patients with uterine cervical cancer treated with image-guided adaptive brachytherapy (IGABT) were selected. Hyaluronic acid gel injection (HGI) was performed in the rectovaginal and vesicouterine septum for 10 patients. The other ten patients were not with HGI. Both groups were treated with IGABT involving tandem/ovoid or cylindrical applicators along with additional interstitial needles. Dose distributions approved by radiation oncologists were retrospectively analyzed, and a dose summation of 45 Gy/25 of external beam radiation therapy and IGABT was performed. Dose constraints for D2cc of bladder, rectum, and sigmoid were 80, 70, and 70 Gy, respectively. Equivalent dose in 2-Gy fractions calculations used α/β = 10 Gy for high-risk clinical target volume (CTVHR) D90 and α/β = 3 Gy for organs at risks (OARs). As a planning study, dose distribution rescaling was conducted to deliver as much dose to CTVHR D90 as possible within the dose constraint limitation for OARs when IGABT was performed for four, three, and two fractions in both groups.

RESULTS

The median CTVHR D90 was >80 Gy in the non-HGI group and >85 Gy in the HGI group for virtual two and three fractions. Rectum D2cc was significantly lower in the HGI group for three fractions (p < 0.01).

CONCLUSIONS

In the HGI group, adequate dose delivery to CTVHR could be achieved with a reduced IGABT fraction number while meeting the dose constraints of OARs.

Gynecological technical notes for appropriate spacer injections

BACKGROUND

Despite its efficacy, if adherence to dose constraints for surrounding normal tissues proves unattainable, the risk of late radiation-related adverse events after primary radiotherapy involving brachytherapy remains a noteworthy concern. Some studies suggest that similar to prostate radiotherapy, spacers may potentially reduce doses to surrounding healthy rectal or bladder tissues. However, guidance on spacer injections for gynecologic brachytherapy is scarce, and the optimal anatomical location for spacer placement remains undefined. We discuss maximizing the effects of spacers from an anatomical perspective.

FINDINGS

As vesicovaginal and rectovaginal septa form part of the endopelvic fascia and are not uniform tissues, spacer injection resistance varies. In pelvic organ prolapse surgery, saline is injected into the anterior and posterior vaginal walls as a spacer, and the vagina, vesicovaginal septum, and bladder can be fluidly dissected. Relatively firm vesicovaginal septum tissue is used as a reconstructive organ, whereas rectovaginal septum tissue is less dense. Cervical cancer is invasive, involving surrounding fascia and ligaments. Ideally, the vesicovaginal and rectovaginal septa should be resected in radical hysterectomy. Here, spacer adaptation and the technical details of injection are described. When using ultrasound guidance for spacer injection, the target site should be adequately magnified, and the spacer ideally injected into the incision layer during radical hysterectomy. Finally, posthysterectomy, the intestinal tract may adhere to the vaginal cuffs. Therefore, artificial ascites may be useful; however, the spread depends on perioperative manipulation.

CONCLUSIONS

Anatomical and surgical viewpoints are advantageous for safe, therapeutic, and replicable spacer injection administration.

Hydrogel spacer injection to the meso-sigmoid to protect the sigmoid colon in cervical cancer brachytherapy: A technical report

Purpose

The use of a hydrogel spacer inserted into recto-vaginal fossa is a valuable strategy to mitigate radiation exposure to the rectum during radiation therapy for female pelvic malignancies. However, when the sigmoid colon is in proximity to the cervix, radiation exposure to the sigmoid colon cannot be adequately mitigated with a hydrogel spacer injected into the recto-vaginal fossa. Here, we presented a case, in which a hydrogel spacer was injected into the meso-sigmoid to protect the sigmoid colon.

Material and methods

A 73-year-old female diagnosed with T3b stage IIIC2r uterine cervical cancer (FIGO 2018) underwent high-dose-rate interstitial brachytherapy consisting of 24 Gy in 4 fractions, following concurrent chemoradiotherapy with external beam radiation therapy of 50 Gy in 25 fractions of whole pelvic radiation therapy. In the initial brachytherapy, the sigmoid colon was in close contact with the uterine cervix. In the second brachytherapy, attempts to create a space between the sigmoid colon and uterine cervix using injected artificial ascites were unsuccessful due to rapid absorption of fluid. In the third and fourth brachytherapy fractions, 5 mL of hydrogel was injected into the meso-sigmoid through a pouch of Douglas under trans-rectal ultrasonography guidance. Dose ratio of sigmoid colon D2cc and high-risk clinical target volume (HR-CTV) D90 of each brachytherapy were evaluated.

Results

Dose ratio of the sigmoid colon D2cc to HR-CTV D90 was 1.03, 0.43, 0.56, and 0.47 in each respective brachytherapy session, indicating dose escalation to HR-CTV whilst achieving acceptable sigmoid dose with hydrogel spacer injected into the meso-sigmoid.

Conclusions

The dose ratio of the sigmoid colon to HR-CTV D90 was decreased by introducing a hydrogel spacer into the meso-sigmoid. In cases where the sigmoid colon is in proximity to the cervical tumor, this novel technique can be considered to achieve better clinical outcomes.

MucoUp® as a spacer in brachytherapy for uterine cervical cancer: A first-in-human experience

We first used MucoUp®, a hyaluronic acid used in endoscopic resection, as a spacer in brachytherapy. In five cervical cancer patients, MucoUp® insertion increased a 90% dose of the high-risk CTV to over 80 Gy while decreasing the dose of organs at risk. No related adverse events were observed.

Is it time to modify the Japanese Uterine Cervical Cancer Guidelines to recommend a higher dose for radio-resistant tumors?

Compared with the European or the United States' uterine cervical cancer management guidelines, which aim to deliver >85 Gy EQD2 (the equivalent effective dose in 2 Gy per fraction) to the high-risk clinical target volume (CTVHR) D90 (minimal dose of 90% of the CTVHR), the dose goal of the corresponding Japanese guidelines does not recommend delivering such a high dose to the CTVHR D90. Subsequently, while the rate of late radiation-induced toxicities is reported to be much lower in the Japanese schedule, the local control rate is relatively inferior to that of clinical results reported by the IntErnational study on MRI-guided BRAchytherapy in CErvical cancer study (EMBRACE-I) in which the dose goal for CTVHR D90 was >85 Gy and showed >90% local control regardless of tumor stage. In daily clinical practice, patients with residual disease supposedly due to insufficient total dose delivery are occasionally referred to our hospital for the possibility of re-irradiation, which is not usually recommended because the risk of late severe radiation-induced toxicity is high. In this report, the authors hope to raise a discussion in our community about modifying our treatment guidelines to recommend a higher dose at least for patients with poor response.