Advertisement

Integrating Permanent Interstitial Brachytherapy Using Cesium-131 into the Primary Management of Gynecologic Malignancies: Bringing Back the Old School

      Purpose

      Permanent interstitial brachytherapy (PIB) using free radiation seeds is an often forgotten modality that provides multiple distinct advantages. The relatively low initial dose rate and short half-life of Cesium-131 significantly reduces the exposure to the treating physician and involved medical staff compared to previously used permanent isotopes. Re-irradiation using Cesium-131 PIB has been described as a management option for recurrent disease. This report presents our experience incorporating its use in up-front management of Gyn malignancies.

      Materials and Methods

      The records of 21 consecutive patients were retrospectively reviewed, all of whom were treated for a gynecologic malignancy using Cesium-131 PIB as a component of definitive therapy. Local failure was defined as a recurrence within the irradiated organ (vagina or vulva). Maximum doses to gross disease and normal tissues were calculated using equivalent dose at 2Gy per fraction (EQD2), outcomes were estimated from the time in months from the date of PIB, and toxicities were scored according to CTCAE v4.0.

      Results

      Reasons for performing PIB included a boost to gross disease for endometrioid adenocarcinoma (EAC) of the uterus (5), squamous cell carcinoma (SCC) of the cervix (1), vaginal SCC (3), vaginal melanoma (3), and vulvar SCC (2); and as a boost for close or positive margins in EAC (4), SCC of the cervix (1), and SCC of the vulva (2). Combined with a median dose of external beam RT of 45 Gy (range 30-64.8 Gy), the median dose delivered using PIB was 22 Gy (range 15-50 Gy) using a median 13 Cesium-131 sources (range 9-30), with median strength of 0.76 u/seed. The median area of PIB was 6 cm2 (range 2 - 19.25 cm2). All patients received their procedure as an outpatient. Sedation consisted of general anesthesia in 2 patients, and local anesthesia in 19. After a median follow-up period of 10.7 months (3-26.5 mos), there has been no local failures. All patients developed acute grade 1-2 mucosal reactions, and only 1 patient has demonstrated persistent grade 3 reactions beyond 6 months. Compared to equivalent plans using vaginal cylinders, equivalent tumoricidal doses of radiation could be delivered using Cs-131 PIB, while calculated maximum doses in EQD2 to normal tissues such as rectum and bladder could consistently be reduced by as much as 20% using PIB.

      Conclusions

      PIB using Cs-131 is an effective treatment modality for incorporation into primary management of gynecologic cancers. The technique benefits from a low rate of morbidity and a very high local control.