Tairo Kashihara

Technical report on the first clinical use of a bioabsorbable PGA spacer in HDR brachytherapy for recurrent cervical cancer

Abstract In recurrent gynecologic malignancies following prior pelvic irradiation, definitive radiation therapy is often precluded by cumulative dose constraints to adjacent organs at risk (OARs), and patients may be left with only highly invasive surgical options such as total pelvic exenteration. While some institutions have explored displacement techniques such as artificial ascites or hyaluronic acid gel injection, these approaches are not widely adopted and frequently fail to ensure consistent and stable separation of OARs. We report the first clinical use of Neskeep®, a bioabsorbable polyglycolic acid (PGA) spacer, in high-dose-rate (HDR) brachytherapy for recurrent cervical cancer after prior pelvic radiation. A woman in her 40s with prior hysterectomy and HDR brachytherapy for cervical intraepithelial neoplasia grade III developed vaginal stump recurrence 4 years later. Laparoscopic placement of the PGA spacer was performed to achieve durable displacement of the small bowel, followed by eight fractions of HDR brachytherapy. Hyaluronic acid gel was also injected during each fraction to displace the bladder and rectum. The spacer maintained position and volume throughout treatment without complications. Dose–volume analysis showed a marked reduction in small bowel D₂cc (mean equivalent dose in 2 Gy fractions (EQD₂): 121.6 cGy) compared to the initial treatment (606.0 cGy), while the spacer itself received a mean D₂cc of 690.3 cGy. MRI confirmed complete response at 2 months, with no adverse events observed at that time point. The PGA spacer enabled safe, curative reirradiation in a case that would otherwise be unsuitable for further radiation therapy.

Configuration analysis of the injection position and shape of the gel spacer in gynecologic brachytherapy

In this single-institution retrospective study, configuration analysis was performed to determine the optimal location and volume of hyaluronic acid gel spacer injection into the rectovaginal or vesicovaginal septum for effective dose reduction (DR) to the organs at risk (OARs), the rectum and bladder. 70 and 50 intracavitary brachytherapy treatment plans used only vaginal cylinders with gel spacers for the rectal and bladder sides, respectively, whereas 28 did not use spacers. Correlation analysis was performed between the geometrical parameters and injection position of the gel spacers and the 2-cm A higher DR was predicted for hyaluronic acid gel spacer injection within ±5 mm and ±2.5 mm in the lateral-medial direction from the midpoint on the rectal and bladder sides, and ±10 mm in the cranial-caudal direction from the midpoint on the rectal side. There were correlations between 2-cm A gel spacer volume of ∼10 cm

A case report of a patient with bulky uterine cervical neoplasm who achieved complete response with “intentional internal high-dose policy” high-dose-rate interstitial brachytherapy

Abstract Rationale Gynecological high-dose-rate (HDR) brachytherapy has progressed for years, but it remains difficult for bulky tumors to be controlled locally. Dose limitations to organs at risk (OARs) are invariably obstacles in increasing the prescription dose. Additionally, it is controversial that the excessive hyperdose sleeve, the volume receiving a dose equal to or greater than twice the reference dose, should be eliminated in gynecological HDR brachytherapy. On the other hand, the technique of simultaneous integrated protection was reported for large hepatocellular carcinoma treatment, and similarly, internal high-dose brachytherapy could be used for treating bulky cervical carcinoma. Patient Concerns A 54-year-old female had irregular genital bleeding and lost 13 kg in one year. Diagnosis She was diagnosed with T3bN1M0 cervical cancer in another hospital. The transverse diameter of the primary tumor was 10.5 cm. Interventions The whole pelvis and para-aortic lymph node were irradiated with a total of 50 Gy in 25 fractions, but the size of the tumor showed only a slight decrease to 8.9 cm. After external beam radiotherapy, first-time high-dose-rate interstitial brachytherapy (HDR-ISBT) was administered without “intentional internal high-dose (IIHD) policy,” the technique of high-dose administration to only the inside of the tumor. Considering the rectum dose limitation, in the additional 2 times of brachytherapy, “IIHD policy” HDR-ISBT was applied. In the second and third HDR-ISBT, the percentage of the volume exposed to 200% of the prescribed dose for high-risk clinical target volume increased by 241% and 204% compared with the first HDR-ISBT, while the doses to OARs were not significantly higher than those of the first-time HDR-ISBT. Outcomes Complete response was obtained, and no recurrence findings and side effects caused by HDR-ISBT have been detected for 2 years and 9 months. Lessons To our knowledge, this is the first report of IIHD HDR-ISBT for bulky cervical cancer. This technique can be the solution for treating bulky cervical cancer.

Salvage image-guided freehand interstitial brachytherapy for pelvic sidewall recurrence after hysterectomy for uterine malignancies

Pelvic sidewall recurrence after hysterectomy for uterine malignances has a poor prognosis, and the salvage therapy for this type of recurrence is still challenging. The purpose of this study was to investigate the efficacy of freehand high-dose-rate interstitial brachytherapy (HDR-ISBT) through the perineum using transrectal ultrasonography for this disease. We retrospectively evaluated 42 patients with pelvic sidewall recurrence after hysterectomy for uterine cervical and endometrial cancers. We investigated patients' characteristics, the 2-year local control and survival rates, and late adverse events of the rectum and bladder. The 2-year overall survival, local control, and progression-free survival rates were 73.7% (95% confidence interval [CI], 60.8-89.3%), 69.4% (95% CI, 55.4-80.1%), and 37.3% (95% CI, 24.6-56.5%), respectively. In Cox multivariate analysis, tumor size at recurrence (<45 mm vs. ≥45 mm) (p = 0.04) and disease-free periods after hysterectomy (<10 months vs. ≥10 months) (p < 0.01) were significant prognostic factors for overall survival. Lymph node metastasis at recurrence (p < 0.01) was also a significant prognostic factor for progression-free survival. Three patients experienced Grade 3-4 late proctitis (7%). Transperineal freehand salvage HDR-ISBT using transrectal ultrasonography was demonstrated to be a curative treatment option for patients with pelvic sidewall recurrence following hysterectomy. Based on the findings of this study, we emphasize the importance of HDR-ISBT for pelvic sidewall recurrence.