Transition from pulsed dose rate to high dose rate brachytherapy: Experience of a single centre.

Background: In February 2021, the Brachytherapy department of the Lorraine Cancer Institute began a transition away from pulsed dose rate (PDR) towards high dose rate (HDR) brachytherapy, for gynaecological cancer, cancers of the oral cavity, oropharynx and anal canal, penile cancer and sarcoma. We describe our experience here; for the benefit of other brachytherapy departments that may be envisaging a similar transition in care.

Medical viewpoint: Fractionation. The 7 brachytherapists of our unit performed a literature search then validated, in a group meeting, the different fractionation regimens. The aim was to select HDR fractionation regimens that would produce comparable results to PDR in terms of tumor control and toxicity, following the recommendations of the GEC-ESTRO, when such guidelines exist. We also chose fractionation regimens that would avoid patients having the brachytherapy device in place over the weekend. The most difficult decisions related to rare indications where only very small series exist. Cohorts of patients treated with HDR will be followed up closely over time. To date, no unexpected toxicity has been observed. It is no longer necessary to have a physician on call at night.

Medical physicist's viewpoint: The discontinuation of PDR has made it possible to reduce the number of radiation sources present in the department, with a reduction of the working time needed for changing out radiation sources and for quality control. There are no longer any difficulties with night duties since all treatment is now performed during the day, in the presence of a physician during normal workday hours. Changes to the treatment planning schedules have been integrated, notably the calculation of biological equivalents for the most complex gynecological dosimetries.

Radiation therapists' viewpoint: The work organization changed markedly, requiring the presence of at least 2 radiation therapists on treatment days, whereas previously, radiation therapists were mainly present on the days of insertion and removal of the brachytherapy source applicators. The schedule for the HDR delivery platform is similar to that of the radiotherapy accelerator. The radiation therapist team has observed benefits in terms of treatment safety, with visual control of the positioning of the equipment before each session, but also in terms of relations with the patient, with more regular interactions with patients. This creates a better atmosphere of trust for implant removal.

Conclusion: With meticulous preparation and close collaboration between the different professions involved in brachytherapy delivery, the transition from PDR to HDR led to significant organizational changes in terms of treatment planning for different cancer sites. Nevertheless, overall, the whole team is satisfied with the new work model. The involvement of all the team members made it possible to anticipate and prepare, enabling a seamless and serene transition towards the scheduled termination of PDR.