[Brachytherapy for prostate cancer: high dose rate or low-dose rate?]

Low-dose brachytherapy for prostate cancer was actually proposed in the first years of the XXth century. Its modern version (iodin 125 or palladium 103 permanent implants) now benefits from some 15 years of experience in a few pioneer centers, with very satisfactory results in term of efficacy/toxicity ratio. More recently, a high-dose rate (HDR) prostate brachytherapy technique has been introduced. Initially utilized essentially as a "boost" irradiation combined with external radiotherapy, it is now being proposed by some authors as a monotherapy for selected localized prostate cancers. Although sophisticated radiobiological models have been proposed to compare those two dose-rates, they are not considered to be valid and reliable enough to compare such different irradiation schemes (A low-dose rate irradiation lasting several months vs a few high-dose fractions given in a few days). When it comes to the implantation techniques, it seems that most of the technical problems which arose for both schemes have been solved, and that the experience of a given team is now much more important than the technique itself. Clinical results cannot be reliably compared so far, the follow-up of the patients treated by HDR brachytherapy being usually shorter, and the patients treated with HDR usually presenting with more advanced lesions. Radioprotection features are very different, with no accident reported for low-dose rate implants. For HDR no irradiation is given at all to the staff and family during a normal application, but one has to face the threat of manipulating high activity sources, with a few accidents or incidents reported in the literature. Financial studies show that for more than 20-30 patients treated in a year, HDR is more economical, although a decrease in the cost of the seeds could change the picture. In conclusion, for low-risk localized prostate cancer, it does not appear reasonable to give up using a low-dose rate technique, which proved to be both efficient and poorly toxic. This actually corresponds to the recent GEC-ESTRO recommendations. For the other patients, a dose escalation is appealing: this could be performed using brachytherapy (LDR or HDR), with or without hormonotherapy. Several trials are ongoing or will be activated very soon to try and answer.