GSOR23 Presentation Time: 12:20 PM: Clinical Outcomes of Interstitial High-Dose Rate Brachytherapy with and without Concurrent Interstitial Hyperthermia for Gynecologic Malignancies

Abstract

<h3>Purpose</h3> Radiosensitization with external hyperthermia (HT) has demonstrated improved oncologic outcomes for patients with gynecological (GYN) malignancies. However, similar data for multicatheter interstitial HT (IHT) with interstitial high-dose rate (IHDR) brachytherapy is limited. We present a single-institution experience of patients with GYN cancers treated using IHDR with and without concurrent IHT (IHDR-IHT). <h3>Materials and Methods</h3> We retrospectively analyzed 63 patients with locally advanced GYN malignancies treated with IHDR using a Syed-Neblett template (IHDR: 29 and IHDR-IHT: 34 patients). Primary indication for adding IHT was bulky, residual or recurrent disease guided by number, location and geometry of needle placement within HRCTV to allow placement of IHT antennae and thermistors. IHT (target temperature 40-44°C) was performed after IHDR treatment using the same set of interstitial catheters. The median age was 60 yrs (27- 89). Primary sites included cervical (n=40), endometrial (n=9), vaginal (n=10), vulvar (n=3), and non-GYN malignancy with vaginal invasion (n=1). Pelvic radiation therapy was performed prior to IHDR in all but one patient with median dose of 45 Gy (Range, 30.6-55.0 Gy) and 52 patients received concurrent chemotherapy. Median IHDR dose was 23.75 Gy (10-30.0) and number of fractions was 5 (2-5). IHDR and IHDR-IHT groups had similar proportion of reirradiation (p=0.55), stage ≥ III (p=0.11) and HRCTV volume (p=0.65) with marginally higher recurrent cases in the IHDR cohort (p=0.07). Median D90 HRCTV EQD2 was higher in IHDR-IHT (78.2 Gy; 14-105) vs IHDR group (75.9 Gy; range 61-86); p = 0.005. Respective median HRCTV volume were 61.3 cc (25-376) and 48.6 cc (12-175); p = 0.21. Chi -square and Mann-Whitney tests were done to compare variables between the two cohorts. The Kaplan-Meier method with Cox Regression was used to estimate overall survival (OS), local control (LC), locoregional control (LRC) and distant control (DC) and evaluate predictors of LC. <h3>Results</h3> IHDR-IHT and IHDR were well tolerated with no acute procedure-related adverse events. With a median follow up of 12.1 months (<1-59) in IHDR group and 11.0 months (1-76), 1 IHDR-HT patient developed acute CTCAE grade 3+ toxicity (grade 3 urinary obstruction in a patient with horseshoe kidney). Late Grade 3+ toxicity was seen in 9 patients (IHDR: 5, IHDR-IHT: 4 patients); ureteral stricture/incontinence (4), fistula (3) and radiation proctitis (2). Median OS was 31 versus 42 months (p=0.55) in the IHDR and IHDR-IHT groups, respectively. 1 yr LC for IHDR vs IHDR-IHT of 86.9% vs 77.8% (p=0.051). Corresponding, 1-yr LRC and DC were 82.5 vs 74.8% (p=0.056) and 81 vs 77.6% (p=0.84), respectively. On cox regression undergoing IHT (HR 4.7 [95% CI 1.3-16.9] p=0.02) was associated with worse local control. <h3>Conclusions</h3> To our knowledge, this is the largest report describing outcomes from the addition of IHT to IHDR in patients with locally advanced GYN malignancies. Use of IHT had excellent tolerance without any procedural complications. With possible group imbalances, trend to shorter LC and LRC was seen in IHT. Prospective controlled studies will be needed to evaluate clinical benefits.