Does microwave interstitial hyperthermia prior to high-dose-rate brachytherapy change prostate volume or therapy plan parameters?
Purpose: In this prospective preliminary study we evaluated changes of prostate volume and changes of brachytherapy treatment plan parameters due to interstitial hyperthermia (IHT) applied prior to high-dose-rate brachytherapy (HDRBT), compared to our standard HDRBT procedure. Material and methods: In a group of 60 consecutive patients with prostate adenocarcinoma, 30 were treated with HDRBT alone and 30 with IHT preceding HDRBT. Prior to catheter implantation, a ‘virtual’ treatment plan (VP) was complied, a ‘live’ plan (LP) was prepared before patient irradiation, and a ‘post’ plan (PP) was drawn up after completing the irradiation procedure. In each plan, based on transrectal ultrasound images, the contours of the prostate, urethra, and rectum were delineated and the respective volumes and dose–volume histogram parameters were evaluated. These parameters, established for the LP, were then compared with those of the PP. Results: Changes in prostate volume and in parameters of the treatment plans were observed, but differences between the two patient groups were not statistically significant. For all 60 patients treated, the average prostate volume in the VP was 32 cm3, in the LP 41 cm3, and the PP 43 cm3. Average values of relative changes in the therapy planning parameters between LP and PP were for the prostate D90 −5.7%, V100 −5.6%, V200 −13.2%, for the urethra D0, 1 cm3 −1.6%, and for rectum D2 cm3 0%. Conclusion: Hyperthermia prior to HDRBT does not significantly change the volume of the prostate and there is no need to perform the new treatment plan after the hyperthermia session.