High-dose-rate brachytherapy as monotherapy for prostate cancer: technique, rationale and perspective

Abstract

High-dose-rate (HDR) brachytherapy as monotherapy is a comparatively new brachytherapy procedure for prostate cancer. Although clinical results are not yet mature enough, it is a highly promising approach in terms of potential benefits for both radiation physics and radiobiology. In this article, we describe our technique for monotherapeutic HDR prostate brachytherapy, as well as the rationale and theoretical background, with educational intent.

Keywords: high-dose-rate (HDR) brachytherapy; hypofractionation; monotherapy; prostate cancer; radiotherapy.

Fig. 1

A) Preparation for implant of applicator needles for HDR prostate brachytherapy. An in-house “see-through” template and its cover plate (center), an in-house metallic frame to hold and connect the template with an ultrasonography- probe stepper (right), applicator needles with stoppers (left), and their screws and screw drivers (upper). B) Needle implant under real-time transrectal-ultrasonography guidance. The patient is awake, under epidural anesthesia, in lithotomy position. Template holes had been superimposed on the ultrasonography monitor. C) Fixation of the template with elastic tape. Before taping, the template had been sutured to the perineal skin. Needle stoppers are sandwiched by the template and its cover plate, preventing needle displacement

Fig. 2

A) Three-dimensional reconstruction of the prostate and proximal seminal vesicles (pink), rectum (green), bladder (blue), urethra (cyan), and applicator needles and source dwell positions (red). Dwell positions were automatically selected by designating the area up to 7-mm outside the prostate or seminal vesicles. Note that some needles and dwell positions were entirely outside the prostate grand and/or partly in the seminal vesicles or in the bladder pouch. B) A dose distribution plot of transverse plane. Note that the urethral dose was < 125% of the prescription dose, and the rectal dose < 75%. Most parts of the rectum received < 50% of the prescription dose, which would be difficult to achieve with EBRT (even with IMRT)

Fig. 3

Treatment planning CT on the implant day (magenta) and on the last irradiation day (Day 4, gray), which were overlaid by matching positions of the metallic fiducial marker (VISICOIL^®). Note that the geometry of needle fiducial template was kept constant, in contrary to the shift of pubic symphysis or sacral bone. However, the needles moved about 1 cm in the caudal direction, together with the template, which might be attributable to the perineal edema