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.

Purpose: 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). Methods: 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 90 (CEM43T 90 ) 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. Results: The temperature metrics, CEM43T 90 , 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 90 below a median of 2.4 min. The rates of acute and late grade-3 toxicities were 10% and 14%, respectively. Conclusion: The reproducibility of HT parameters between sessions was high. A moderately high CEM43T 90 (> 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.