ESTRO meets Asia 2024 - Abstract Book

S291

Interdisciplinary – Urology

ESTRO meets Asia 2024

289

Proffered Paper

High thermal dose improves effect in non-muscle-invasive bladder cancer treated with MMC and heating

C. Paola Tello Valverde 1 , Debby Geijsen 1 , Akke Bakker 1 , Jorg Oddens 2 , Theo de Reijke 2 , Petra Kok 1 , Hans Crezee 1

1 Department of Radiation Oncology, Amsterdam UMC, Amsterdam, Netherlands. 2 Department of Urology, Amsterdam UMC, Amsterdam, Netherlands

Purpose/Objective:

Incidence of recurrences remain high for patients with non-muscle-invasive bladder cancer (NMIBC) despite different adjuvant intravesical therapies. Previous studies showed a clear advantage of hyperthermia combined with mitomycin C (MMC) compared to MMC alone. 1,2,3 Thermal dose-effect on clinical outcomes in non-muscle invasive bladder cancer (NMIBC) have not yet been investigated. We aimed to investigate the effect of hyperthermia thermal dose (TD) on recurrence-free survival (RFS) and in relation to acute toxicity in patients with NMIBC treated with chemohyperthermia.

Material/Methods:

In this historical cohort study (#NL5636), 60 patients with high-risk NMIBC treated with six weekly sessions of locoregional chemohyperthermia with MMC followed by four maintenance sessions between 2009 and 2020 were included. Temperature was monitored with multisensor thermocouple probes in the bladder and bladder region (i.e. urethra, rectum and, if applicable, vagina). Groups were divided using an outcome-related cut-off point into ‘low’ (n= 30; < 16.6 min) and ‘high’ (n= 30; ≥ 16.6 min) TD groups by the total CEM43T50 (=median cumulative equivalent minutes at 43°C) from the bladder region. Actuarial RFS, and acute toxicity (CTCAE v5.0= common terminology criteria of adverse events version 5.0) were analyzed. Multivariate Cox regression and inverse probability weighting (IPW) analysis were performed. The maximum of three potential confounders were calculated and included in the analysis. Confounders included were based on clinical literature, such as sex, pathological stage, and number of treatment sessions. Median time to recurrence was 1.7 years (interquartile range 0.8 – 4.3 years). RFS rates for the whole group at one-, two- and three-year were 76.5%, 57.2% and 46.4%, respectively. Actuarial RFS was significantly higher in the high TD group than in the low group ( P = 0.028, Figure 1). For the low and high TD groups, the RFS rates at one-, two- and three-year were 72.9% vs. 80.0%, 48.7% vs. 65.7% and 27.0% vs. 65.7%, respectively. These RFS rates remain stable at four and five years. After adjusting for pre-specified potential confounders, the effect of high TD in the bladder region remained significant on RFS (low vs. high; adj. HR 2.5; 95% CI 1.1 – 5.7; P = 0.031). IPW analysis (low vs. high; HR 2.5; 95% CI 1.9 – 3.1, P = 0.031) confirmed this result. Acute toxicity was not significantly different between low and high TD groups ( P = 1.00). Grade 1 and grade 2 toxicity was observed in 63.3% (n= 38) and 31.7% (n= 19) of the patients, respectively. No grade ≥ 3 toxicity was reported. The only two reported grade 2 toxicities were bladder spasm (n= 13, 21.7%) and allergic reaction (n= 8, 13.3%), Table 1. Results: