Radiotherapy combined with deep regional hyperthermia in elderly and frail patients with muscle-invasive bladder cancer: quality analysis of hyperthermia and impact on clinical results.

Radiotherapy (RT) in combination with deep regional hyperthermia (HT) after transurethral removal of bladder tumor (TURBT) can be offered to elderly and frail patients with muscle-invasive bladder cancer (MIBC). In total, 21 patients (mean age 84 years) with unifocal or multifocal MIBC received radiation to a dose of 48-50 Gy/16-20 fractions with weekly HT. The primary endpoint was the variation in temperature metrics, thermal dose expressed as cumulative equivalent minutes at 43 °C when the measured temperature is T (CEM43T) and net power applied in target volume per each HT session. Secondary endpoints were three-year overall survival (OS), disease-free survival (DFS), local progression-free survival (LPFS) and toxicity. The temperature metrics, CEM43T, mean and maximum net power applied did not differ significantly among the HT sessions of the 21 patients. With a median follow-up of 65 months, 52% (95% CI 32-72%) of patients had died 3 years after treatment. The three-year DFS and LPFS rates were 62% (95%CI 41-79%) and 81% (95%CI 60-92%), respectively. The three-year bladder preservation rate was 100%. Three out of four patients with local failure received a thermal dose CEM43T below a median of 2.4 min. The rates of acute and late grade-3 toxicities were 10% and 14%, respectively. The reproducibility of HT parameters between sessions was high. A moderately high CEM43T (> 2.4 min) for each HT session seems to be preferable for local control. RT combined with HT is a promising organ-preservation therapy for elderly and frail MIBC patients.