Pulsed dose rate brachytherapy – is it the right way?

Abstract

Pulsed dose rate (PDR-BT) treatment is a brachytherapy modality that combines physical advantages of high-dose-rate (HDR-BT) technology (isodose optimization, radiation safety) with the radiobiological advantages of low-dose-rate (LDR-BT) brachytherapy. Pulsed brachytherapy consists of using stronger radiation source than for LDR-BT and producing series of short exposures of 10 to 30 minutes in every hour to approximately the same total dose in the same overall time as with the LDR-BT. Modern afterloading equipment offers certain advantages over interstitial or intracavitary insertion of separate needles, tubes, seeds or wires. Isodose volumes in tissues can be created flexibly by a combination of careful placement of the catheter and the adjustment of the dwell times of the computerized stepping source. Automatic removal of the radiation sources into a shielded safe eliminates radiation exposures to staff and visitors. Radiation exposure is also eliminated to the staff who formerly loaded and unloaded multiplicity of radioactive sources into the catheters, ovoids, tubes etc. This review based on summarized clinical investigations, analyses the feasibility and the background to introduce this brachytherapy technique and chosen clinical applications of PDR-BT.

Dose Rate Definition in Brachytherapy

“…This produces treatment dose rates of up to about 3 Gy/h, which can be utilized (pulsed) every hour, 24 pulses per day. [2,3] Table 1 shows the BRT dose rates and the most common clinical applications.…”

“…If these conditions are met, the biological effects of PDR radiation therapy should be equivalent to those of LDR BRT for all tissues. [3,33,34] The advantages and disadvantages of PDR BRT can be listed as follows [3]:…”

High precision radiotherapy including intensity-modulated radiation therapy and pulsed-dose-rate brachytherapy for cervical cancer: a retrospective monoinstitutional study

“…Concern-ing BT, radiation therapy centres around the world transited from low-dose-rate (LDR) to remote after-loading high-dose-rate (HDR) keeping the same oncological result, as demonstrated in a number of randomized trials [10,11,12,13,14,15,16]. A third type of BT is pulsed-doserate (PDR), developed in the 1990s, which combines the radiation safety advantages of after-loading technology and isodose optimization of HDR-BT (applicators and treatment planning system are the same and after-loaders are quite similar) with the theoretical radiobiological advantage of LDR-BT, due to the incomplete repair of the sub-lethal damage between two succeeding pulses [17,18]. From an organizational point of view, PDR-BT is similar to LDR-BT in terms of the dedicated shielded room and nursing care.…”

Pulsed-Dose Rate Brachytherapy for the Treatment of Endometrial Cancer

“…In fact, the interval between pulses carries a radiobiological disadvantage, increasing late normal tissue reactions. But, normally, in PDR schedules this gap is not sufficient to allow the complete repair of sublethal damage, thus the increased radiobiological effect on late-responding normal tissues is limited [19] .…”